I am looking to build an amp for home theatre/hifi use.
currently have an amp using Hitachi's default design for mos fets from the 
'80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and ipl 
acoustics tl4 speakers at the front and Ariston ( small black tubular things 
that sound quite good ) at the back.

I plan using LM4702 but have three options for the output stage.

bipolar
SAP15P and SAP15N
2SA1943 and 2SC5200
mosfet
2SK1530 and 2SJ201

I know I'm inviting WW3 but would there be any differance in sound between 
them ?

Pete

In article <4af03f39$0$2492$db0fefd9@news.zen.co.uk>, Pete
 wrote:
> I am looking to build an amp for home theatre/hifi use. currently have
> an amp using Hitachi's default design for mos fets from the '80's (
> 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and ipl
> acoustics tl4 speakers at the front and Ariston ( small black tubular
> things that sound quite good ) at the back.

> I plan using LM4702 but have three options for the output stage.

> bipolar SAP15P and SAP15N 2SA1943 and 2SC5200 mosfet 2SK1530 and 2SJ201

> I know I'm inviting WW3 but would there be any differance in sound
> between them ?

No need for WW3 since no meaningful answer is possible without knowing the
actual details of the designs which use them, and more info on the use. :-)

The main thing you could tell from the above is the max power / current /
voltage you might be able to drive. But if that is 'sufficient' for your
speakers and listening level that becomes irrelevant to the choice. 

If the SAP devices are of the type that are darlingtons with the internal
thermal compensation diodes, then they may make thermal stability easier.
But I personally never liked darlingtons or power fets as I found they
tended to be prone to ultrasonic hooting. But YMMV. The SAP and mosfets can
make driving and biassing easier. That said I am old fashioned so am most
comfortable with using simple bipolar output devices.

Slainte,

Jim

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

"Pete"  wrote in message 
news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>I am looking to build an amp for home theatre/hifi use.
> currently have an amp using Hitachi's default design for mos 
> fets from the '80's ( 2sk49 2sj50 I think ). It is used with a 
> tagmclaren av32r  and ipl acoustics tl4 speakers at the front 
> and Ariston ( small black tubular things that sound quite 
> good ) at the back.
>
> I plan using LM4702 but have three options for the output 
> stage.
>
> bipolar
> SAP15P and SAP15N
> 2SA1943 and 2SC5200
> mosfet
> 2SK1530 and 2SJ201
>
> I know I'm inviting WW3 but would there be any differance in 
> sound between them ?
>
> Pete
>
>
>
>

Why bother? The basic Hitachi design is as good as it gets. You 
can improve things by building aproper regulated power supply for 
it.

Mine, on Ambit boards, was dual mono with regulated PSUs designed 
by John Lindsey Hood would do about 112W at the onset of limiting 
into 8R and 224W at the onset of limiting into 4R. In 'normal' 
use it barely got warm. It was as flat as a pancake (OK +/- 
0.2dB) from about 12Hz to well over 100KHz, with maximum phase 
error of about 2 deg at 12Hz and about 80KHz. Surely that's good 
enough for anybody?


-- 
Woody

harrogate three at ntlworld dot com

"Pete"  wrote in message 
news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>I am looking to build an amp for home theatre/hifi use.
> currently have an amp using Hitachi's default design for mos fets from the 
> '80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and ipl 
> acoustics tl4 speakers at the front and Ariston ( small black tubular 
> things that sound quite good ) at the back.
>
> I plan using LM4702 but have three options for the output stage.
>
> bipolar
> SAP15P and SAP15N
> 2SA1943 and 2SC5200
> mosfet
> 2SK1530 and 2SJ201
>
> I know I'm inviting WW3 but would there be any differance in sound between 
> them ?

**Depends on implementation. The MOSFETs, of course, will always sound like 
MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200 
devices are amongst the most advanced, lowest distortion output devices 
developed. The SAP15s are easy and convenient to implement, but you run the 
risk of using a device unique to a single manufacturer. Once that 
manufacturer deletes them from the product line-up, you'll be screwed for 
spare parts later on. Personally, I like the 2SA1943/2SC5200 devices, 
Collectors coupled to the load.


-- 
Trevor Wilson
www.rageaudio.com.au

On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
 wrote:

>
>"Pete"  wrote in message 
>news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>>I am looking to build an amp for home theatre/hifi use.
>> currently have an amp using Hitachi's default design for mos fets from the 
>> '80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and ipl 
>> acoustics tl4 speakers at the front and Ariston ( small black tubular 
>> things that sound quite good ) at the back.
>>
>> I plan using LM4702 but have three options for the output stage.
>>
>> bipolar
>> SAP15P and SAP15N
>> 2SA1943 and 2SC5200
>> mosfet
>> 2SK1530 and 2SJ201
>>
>> I know I'm inviting WW3 but would there be any differance in sound between 
>> them ?
>
>**Depends on implementation. The MOSFETs, of course, will always sound like 
>MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200 
>devices are amongst the most advanced, lowest distortion output devices 
>developed. The SAP15s are easy and convenient to implement, but you run the 
>risk of using a device unique to a single manufacturer. Once that 
>manufacturer deletes them from the product line-up, you'll be screwed for 
>spare parts later on. Personally, I like the 2SA1943/2SC5200 devices, 
>Collectors coupled to the load.

Compressed? You can of course produce a transfer characteristic to
back this up? As far as I am aware it is perfectly possible to produce
a MOSFET design without a trace of compression - which would of course
show up as an unimaginably huge distortion figure.

d

"Don Pearce"  wrote in message 
news:4af19415.34158250@news.eternal-september.org...
> On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
>  wrote:
>
>>
>>"Pete"  wrote in message
>>news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>>>I am looking to build an amp for home theatre/hifi use.
>>> currently have an amp using Hitachi's default design for mos fets from 
>>> the
>>> '80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and 
>>> ipl
>>> acoustics tl4 speakers at the front and Ariston ( small black tubular
>>> things that sound quite good ) at the back.
>>>
>>> I plan using LM4702 but have three options for the output stage.
>>>
>>> bipolar
>>> SAP15P and SAP15N
>>> 2SA1943 and 2SC5200
>>> mosfet
>>> 2SK1530 and 2SJ201
>>>
>>> I know I'm inviting WW3 but would there be any differance in sound 
>>> between
>>> them ?
>>
>>**Depends on implementation. The MOSFETs, of course, will always sound 
>>like
>>MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
>>devices are amongst the most advanced, lowest distortion output devices
>>developed. The SAP15s are easy and convenient to implement, but you run 
>>the
>>risk of using a device unique to a single manufacturer. Once that
>>manufacturer deletes them from the product line-up, you'll be screwed for
>>spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
>>Collectors coupled to the load.
>
> Compressed?

**Yep.

You can of course produce a transfer characteristic to
> back this up?

**Negative Tempco of gm.

 As far as I am aware it is perfectly possible to produce
> a MOSFET design without a trace of compression - which would of course
> show up as an unimaginably huge distortion figure.

**What can I say? It what they sound like, when operating in low bias Class 
A/B. When operating in high bias Class A/B or Class A, they show no signs of 
compression. At low currents, they suck. Ask anyone who has taken the time 
to do a double blind listen. I have. Many times. Shockers.


-- 
Trevor Wilson
www.rageaudio.com.au

On Wed, 4 Nov 2009 07:52:21 +1100, "Trevor Wilson"
 wrote:

>
>"Don Pearce"  wrote in message 
>news:4af19415.34158250@news.eternal-september.org...
>> On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
>>  wrote:
>>
>>>
>>>"Pete"  wrote in message
>>>news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>>>>I am looking to build an amp for home theatre/hifi use.
>>>> currently have an amp using Hitachi's default design for mos fets from 
>>>> the
>>>> '80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and 
>>>> ipl
>>>> acoustics tl4 speakers at the front and Ariston ( small black tubular
>>>> things that sound quite good ) at the back.
>>>>
>>>> I plan using LM4702 but have three options for the output stage.
>>>>
>>>> bipolar
>>>> SAP15P and SAP15N
>>>> 2SA1943 and 2SC5200
>>>> mosfet
>>>> 2SK1530 and 2SJ201
>>>>
>>>> I know I'm inviting WW3 but would there be any differance in sound 
>>>> between
>>>> them ?
>>>
>>>**Depends on implementation. The MOSFETs, of course, will always sound 
>>>like
>>>MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
>>>devices are amongst the most advanced, lowest distortion output devices
>>>developed. The SAP15s are easy and convenient to implement, but you run 
>>>the
>>>risk of using a device unique to a single manufacturer. Once that
>>>manufacturer deletes them from the product line-up, you'll be screwed for
>>>spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
>>>Collectors coupled to the load.
>>
>> Compressed?
>
>**Yep.
>
>You can of course produce a transfer characteristic to
>> back this up?
>
>**Negative Tempco of gm.
>
> As far as I am aware it is perfectly possible to produce
>> a MOSFET design without a trace of compression - which would of course
>> show up as an unimaginably huge distortion figure.
>
>**What can I say? It what they sound like, when operating in low bias Class 
>A/B. When operating in high bias Class A/B or Class A, they show no signs of 
>compression. At low currents, they suck. Ask anyone who has taken the time 
>to do a double blind listen. I have. Many times. Shockers.

Negative tempco makes no difference. The gain of a power amplifier is
set by a pair of feedback resistors. Provided there is sufficient open
loop gain available (and we must assume there is) there can be no
compression. The system will perform at constant gain up to the
clipping point just like any amplifier.

I presume you are treating this as an interview for a job reviewing in
Stereophile?

d

"Don Pearce"  wrote in message 
news:4af299e7.35648796@news.eternal-september.org...
> On Wed, 4 Nov 2009 07:52:21 +1100, "Trevor Wilson"
>  wrote:
>
>>
>>"Don Pearce"  wrote in message
>>news:4af19415.34158250@news.eternal-september.org...
>>> On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
>>>  wrote:
>>>
>>>>
>>>>"Pete"  wrote in message
>>>>news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>>>>>I am looking to build an amp for home theatre/hifi use.
>>>>> currently have an amp using Hitachi's default design for mos fets from
>>>>> the
>>>>> '80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and
>>>>> ipl
>>>>> acoustics tl4 speakers at the front and Ariston ( small black tubular
>>>>> things that sound quite good ) at the back.
>>>>>
>>>>> I plan using LM4702 but have three options for the output stage.
>>>>>
>>>>> bipolar
>>>>> SAP15P and SAP15N
>>>>> 2SA1943 and 2SC5200
>>>>> mosfet
>>>>> 2SK1530 and 2SJ201
>>>>>
>>>>> I know I'm inviting WW3 but would there be any differance in sound
>>>>> between
>>>>> them ?
>>>>
>>>>**Depends on implementation. The MOSFETs, of course, will always sound
>>>>like
>>>>MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
>>>>devices are amongst the most advanced, lowest distortion output devices
>>>>developed. The SAP15s are easy and convenient to implement, but you run
>>>>the
>>>>risk of using a device unique to a single manufacturer. Once that
>>>>manufacturer deletes them from the product line-up, you'll be screwed 
>>>>for
>>>>spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
>>>>Collectors coupled to the load.
>>>
>>> Compressed?
>>
>>**Yep.
>>
>>You can of course produce a transfer characteristic to
>>> back this up?
>>
>>**Negative Tempco of gm.
>>
>> As far as I am aware it is perfectly possible to produce
>>> a MOSFET design without a trace of compression - which would of course
>>> show up as an unimaginably huge distortion figure.
>>
>>**What can I say? It what they sound like, when operating in low bias 
>>Class
>>A/B. When operating in high bias Class A/B or Class A, they show no signs 
>>of
>>compression. At low currents, they suck. Ask anyone who has taken the time
>>to do a double blind listen. I have. Many times. Shockers.
>
> Negative tempco makes no difference. The gain of a power amplifier is
> set by a pair of feedback resistors. Provided there is sufficient open
> loop gain available (and we must assume there is) there can be no
> compression. The system will perform at constant gain up to the
> clipping point just like any amplifier.
>
> I presume you are treating this as an interview for a job reviewing in
> Stereophile?

**I doubt that. I have been critical of Stereophile many times. I have also 
performed several DBTs involving MOSFET amps and BJT amps. The first was way 
back when Perreaux first burst onto the scene with their MOSFET amps. I 
wondered at what I was hearing, so I set up a Phase Linear 400 amp for 
comparison. The Phase Linear was determined (not just by me) to be much more 
dynamic sounding. The only MOSFET amps I've heard which do not suffer this 
problem are those manufactured by Pass Labs.

Tell me about your blind listening experiences with MOSFET amps and BJT 
amps.


-- 
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson"  wrote in
message news:7lbgqcF3cri2oU1@mid.individual.net


> **Depends on implementation. The MOSFETs, of course, will
> always sound like MOSFETs - dull, boring, undynamic and
> compressed.

Sounds like more of the same "every amplifier sounds different religion that 
Trevor has been entertaining many of with for years and years.

It wasn't that long ago that Trevor was making similar claims about power 
amps with that well-known circuit design *failing* known as loop feedback.

So Trevor, which is worse, MOSFETs with or without loop feedback, versus 
bipolars with or without loop feedback?

On Wed, 4 Nov 2009 08:32:19 +1100, "Trevor Wilson"
 wrote:

>
>"Don Pearce"  wrote in message 
>news:4af299e7.35648796@news.eternal-september.org...
>> On Wed, 4 Nov 2009 07:52:21 +1100, "Trevor Wilson"
>>  wrote:
>>
>>>
>>>"Don Pearce"  wrote in message
>>>news:4af19415.34158250@news.eternal-september.org...
>>>> On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
>>>>  wrote:
>>>>
>>>>>
>>>>>"Pete"  wrote in message
>>>>>news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>>>>>>I am looking to build an amp for home theatre/hifi use.
>>>>>> currently have an amp using Hitachi's default design for mos fets from
>>>>>> the
>>>>>> '80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r  and
>>>>>> ipl
>>>>>> acoustics tl4 speakers at the front and Ariston ( small black tubular
>>>>>> things that sound quite good ) at the back.
>>>>>>
>>>>>> I plan using LM4702 but have three options for the output stage.
>>>>>>
>>>>>> bipolar
>>>>>> SAP15P and SAP15N
>>>>>> 2SA1943 and 2SC5200
>>>>>> mosfet
>>>>>> 2SK1530 and 2SJ201
>>>>>>
>>>>>> I know I'm inviting WW3 but would there be any differance in sound
>>>>>> between
>>>>>> them ?
>>>>>
>>>>>**Depends on implementation. The MOSFETs, of course, will always sound
>>>>>like
>>>>>MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
>>>>>devices are amongst the most advanced, lowest distortion output devices
>>>>>developed. The SAP15s are easy and convenient to implement, but you run
>>>>>the
>>>>>risk of using a device unique to a single manufacturer. Once that
>>>>>manufacturer deletes them from the product line-up, you'll be screwed 
>>>>>for
>>>>>spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
>>>>>Collectors coupled to the load.
>>>>
>>>> Compressed?
>>>
>>>**Yep.
>>>
>>>You can of course produce a transfer characteristic to
>>>> back this up?
>>>
>>>**Negative Tempco of gm.
>>>
>>> As far as I am aware it is perfectly possible to produce
>>>> a MOSFET design without a trace of compression - which would of course
>>>> show up as an unimaginably huge distortion figure.
>>>
>>>**What can I say? It what they sound like, when operating in low bias 
>>>Class
>>>A/B. When operating in high bias Class A/B or Class A, they show no signs 
>>>of
>>>compression. At low currents, they suck. Ask anyone who has taken the time
>>>to do a double blind listen. I have. Many times. Shockers.
>>
>> Negative tempco makes no difference. The gain of a power amplifier is
>> set by a pair of feedback resistors. Provided there is sufficient open
>> loop gain available (and we must assume there is) there can be no
>> compression. The system will perform at constant gain up to the
>> clipping point just like any amplifier.
>>
>> I presume you are treating this as an interview for a job reviewing in
>> Stereophile?
>
>**I doubt that. I have been critical of Stereophile many times. I have also 
>performed several DBTs involving MOSFET amps and BJT amps. The first was way 
>back when Perreaux first burst onto the scene with their MOSFET amps. I 
>wondered at what I was hearing, so I set up a Phase Linear 400 amp for 
>comparison. The Phase Linear was determined (not just by me) to be much more 
>dynamic sounding. The only MOSFET amps I've heard which do not suffer this 
>problem are those manufactured by Pass Labs.
>
>Tell me about your blind listening experiences with MOSFET amps and BJT 
>amps.

We're discussing compression, which can be measured objectively -
please don't try to divert the discussion onto the metaphysical. Show
me compression.

d

"Arny Krueger"  wrote in message 
news:kO6dnQHBWPZvPG3XnZ2dnUVZ_gqdnZ2d@giganews.com...
> "Trevor Wilson"  wrote in
> message news:7lbgqcF3cri2oU1@mid.individual.net
>
>
>> **Depends on implementation. The MOSFETs, of course, will
>> always sound like MOSFETs - dull, boring, undynamic and
>> compressed.
>
> Sounds like more of the same "every amplifier sounds different religion 
> that Trevor has been entertaining many of with for years and years.

**I'll make it easy for you. Locate an old Phase Linear 400(b) and an early 
Perreaux amp. Set up a DBT between the two and ask the listeners what 
differences they feel they can hear (if any). Let me know what results you 
find. Both amps are plentiful and cheap, so the test should be an easy one. 
Both amps use shit-loads of global NFB, minimal bias current and primitive 
topology so the only major differences are related to the output devices 
used.

Take the time to listen for yourself. You might be surprised. I was.


-- 
Trevor Wilson
www.rageaudio.com.au

"Don Pearce"  wrote in message 
news:4af3a210.37737421@news.eternal-september.org...
> On Wed, 4 Nov 2009 08:32:19 +1100, "Trevor Wilson"
>  wrote:
>
>>
>>"Don Pearce"  wrote in message
>>news:4af299e7.35648796@news.eternal-september.org...
>>> On Wed, 4 Nov 2009 07:52:21 +1100, "Trevor Wilson"
>>>  wrote:
>>>
>>>>
>>>>"Don Pearce"  wrote in message
>>>>news:4af19415.34158250@news.eternal-september.org...
>>>>> On Wed, 4 Nov 2009 07:06:02 +1100, "Trevor Wilson"
>>>>>  wrote:
>>>>>
>>>>>>
>>>>>>"Pete"  wrote in message
>>>>>>news:4af03f39$0$2492$db0fefd9@news.zen.co.uk...
>>>>>>>I am looking to build an amp for home theatre/hifi use.
>>>>>>> currently have an amp using Hitachi's default design for mos fets 
>>>>>>> from
>>>>>>> the
>>>>>>> '80's ( 2sk49 2sj50 I think ). It is used with a tagmclaren av32r 
>>>>>>> and
>>>>>>> ipl
>>>>>>> acoustics tl4 speakers at the front and Ariston ( small black 
>>>>>>> tubular
>>>>>>> things that sound quite good ) at the back.
>>>>>>>
>>>>>>> I plan using LM4702 but have three options for the output stage.
>>>>>>>
>>>>>>> bipolar
>>>>>>> SAP15P and SAP15N
>>>>>>> 2SA1943 and 2SC5200
>>>>>>> mosfet
>>>>>>> 2SK1530 and 2SJ201
>>>>>>>
>>>>>>> I know I'm inviting WW3 but would there be any differance in sound
>>>>>>> between
>>>>>>> them ?
>>>>>>
>>>>>>**Depends on implementation. The MOSFETs, of course, will always sound
>>>>>>like
>>>>>>MOSFETs - dull, boring, undynamic and compressed. The 2SA1943/2SC5200
>>>>>>devices are amongst the most advanced, lowest distortion output 
>>>>>>devices
>>>>>>developed. The SAP15s are easy and convenient to implement, but you 
>>>>>>run
>>>>>>the
>>>>>>risk of using a device unique to a single manufacturer. Once that
>>>>>>manufacturer deletes them from the product line-up, you'll be screwed
>>>>>>for
>>>>>>spare parts later on. Personally, I like the 2SA1943/2SC5200 devices,
>>>>>>Collectors coupled to the load.
>>>>>
>>>>> Compressed?
>>>>
>>>>**Yep.
>>>>
>>>>You can of course produce a transfer characteristic to
>>>>> back this up?
>>>>
>>>>**Negative Tempco of gm.
>>>>
>>>> As far as I am aware it is perfectly possible to produce
>>>>> a MOSFET design without a trace of compression - which would of course
>>>>> show up as an unimaginably huge distortion figure.
>>>>
>>>>**What can I say? It what they sound like, when operating in low bias
>>>>Class
>>>>A/B. When operating in high bias Class A/B or Class A, they show no 
>>>>signs
>>>>of
>>>>compression. At low currents, they suck. Ask anyone who has taken the 
>>>>time
>>>>to do a double blind listen. I have. Many times. Shockers.
>>>
>>> Negative tempco makes no difference. The gain of a power amplifier is
>>> set by a pair of feedback resistors. Provided there is sufficient open
>>> loop gain available (and we must assume there is) there can be no
>>> compression. The system will perform at constant gain up to the
>>> clipping point just like any amplifier.
>>>
>>> I presume you are treating this as an interview for a job reviewing in
>>> Stereophile?
>>
>>**I doubt that. I have been critical of Stereophile many times. I have 
>>also
>>performed several DBTs involving MOSFET amps and BJT amps. The first was 
>>way
>>back when Perreaux first burst onto the scene with their MOSFET amps. I
>>wondered at what I was hearing, so I set up a Phase Linear 400 amp for
>>comparison. The Phase Linear was determined (not just by me) to be much 
>>more
>>dynamic sounding. The only MOSFET amps I've heard which do not suffer this
>>problem are those manufactured by Pass Labs.
>>
>>Tell me about your blind listening experiences with MOSFET amps and BJT
>>amps.
>
> We're discussing compression, which can be measured objectively -
> please don't try to divert the discussion onto the metaphysical. Show
> me compression.

**DBTs are not metaphysical. They allow REAL differences to be heard. Tell 
me about your experiences with DBTs between MOSFET and BJT amps.


-- 
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson"  wrote
>
> **DBTs are not metaphysical. They allow REAL differences to be heard. Tell 
> me about your experiences with DBTs between MOSFET and BJT amps.
>
I'd be interested to know how these DBTs were conducted. How many listeners 
did you use?, how were they recruited, how much did they know about the 
purpose of the test? etc.

David.

On Wed, 4 Nov 2009 08:47:13 +1100, "Trevor Wilson"
 wrote:

>> We're discussing compression, which can be measured objectively -
>> please don't try to divert the discussion onto the metaphysical. Show
>> me compression.
>
>**DBTs are not metaphysical. They allow REAL differences to be heard. Tell 
>me about your experiences with DBTs between MOSFET and BJT amps.
>

Stop changing the subject. Either there is compression as you claim,
or there is not. Show me evidence of compression.

d

"David Looser"  wrote in message 
news:7lbn69F3cpcudU1@mid.individual.net...
> "Trevor Wilson"  wrote
>>
>> **DBTs are not metaphysical. They allow REAL differences to be heard. 
>> Tell me about your experiences with DBTs between MOSFET and BJT amps.
>>
> I'd be interested to know how these DBTs were conducted. How many 
> listeners did you use?

**10. I arranged for a person who had no knowledge of which amp (he was no 
present at set-up time) was which to throw the switch, whilst keeping a 
record of which position the switch was in at each change. I set the 
equipment up and was present for the test, but took no part.

, how were they recruited, how much did they know about the
> purpose of the test? etc.

**They only knew that there might be a change in the system when the light 
changed from green to red. The listeners were all those who considered 
themselves to be audiophiles. They were not 'people off the street'. I was 
already familiar with the listening preferences of each. They were tested in 
groups of two, over a period of several days.

I performed the test, because I heard about these "new" (back in the early 
1980s) MOSFET amps and how wonderful they allegedly were. I was surprised at 
how bad they sounded, despite glowing reviews in places like Stereophile. I 
decided to recruit others to see if their perceptions agreed with mine. They 
did. All listeners reported similar findings. The MOSFET amps sounded 
'compressed' and lacking in dynamics.


-- 
Trevor Wilson
www.rageaudio.com.au

"Don Pearce"  wrote in message 
news:4af4a78e.39143906@news.eternal-september.org...
> On Wed, 4 Nov 2009 08:47:13 +1100, "Trevor Wilson"
>  wrote:
>
>>> We're discussing compression, which can be measured objectively -
>>> please don't try to divert the discussion onto the metaphysical. Show
>>> me compression.
>>
>>**DBTs are not metaphysical. They allow REAL differences to be heard. Tell
>>me about your experiences with DBTs between MOSFET and BJT amps.
>>
>
> Stop changing the subject. Either there is compression as you claim,
> or there is not. Show me evidence of compression.

**I cannot. Try the test and let me know what you hear. Perhaps you will 
have a different explanation. Negative tempco of gm is the only thing that 
makes sense to me.


-- 
Trevor Wilson
www.rageaudio.com.au

On Wed, 4 Nov 2009 09:12:59 +1100, "Trevor Wilson"
 wrote:

>
>"Don Pearce"  wrote in message 
>news:4af4a78e.39143906@news.eternal-september.org...
>> On Wed, 4 Nov 2009 08:47:13 +1100, "Trevor Wilson"
>>  wrote:
>>
>>>> We're discussing compression, which can be measured objectively -
>>>> please don't try to divert the discussion onto the metaphysical. Show
>>>> me compression.
>>>
>>>**DBTs are not metaphysical. They allow REAL differences to be heard. Tell
>>>me about your experiences with DBTs between MOSFET and BJT amps.
>>>
>>
>> Stop changing the subject. Either there is compression as you claim,
>> or there is not. Show me evidence of compression.
>
>**I cannot. Try the test and let me know what you hear. Perhaps you will 
>have a different explanation. Negative tempco of gm is the only thing that 
>makes sense to me.

We are discussing one single parameter - compression. Once you start
with nonsense like seeing what you hear, you are no longer able to
isolate that parameter - you hear the sum of everything. And of course
mixed in with your "just listen" thing is all your bullshittery with
terms like "more dynamic". This is meaningless drivel, and the
standard recourse of the charlatan trying to claim superior skills of
discernment to the average man. It won't wash. You made the claim, now
substantiate it or withdraw it.

d

"Pete"
>
> I am looking to build an amp for home theatre/hifi use.
> currently have an amp using Hitachi's default design for mos fets from the 
> '80's ( 2sk49 2sj50 I think ).

** Those are Hitachi's famous TO3 pack " lateral " mosfets as used in many 
famous hi-fi and professional power amps.

They are extremely easy to use, exceptionally rugged and have  NO issues 
with biasing or bias stability. Plus they will share current automatically 
when used in parallel.


> I plan using LM4702 but have three options for the output stage.
>
> bipolar
> SAP15P and SAP15N
> 2SA1943 and 2SC5200
>
> mosfet
> 2SK1530 and 2SJ201


** Those Toshiba numbers are  NOT  lateral mosfets at all  -  but switching 
types with a low gate voltage threshold.

Such devices do not have any of the desirable characteristics of the Hitachi 
laterals.

Biasing is a pig, thermal runaway is just itching to happen.


....  Phil

"Don Pearce"  wrote in message 
news:4af5af9a.41203046@news.eternal-september.org...
> On Wed, 4 Nov 2009 09:12:59 +1100, "Trevor Wilson"
>  wrote:
>
>>
>>"Don Pearce"  wrote in message
>>news:4af4a78e.39143906@news.eternal-september.org...
>>> On Wed, 4 Nov 2009 08:47:13 +1100, "Trevor Wilson"
>>>  wrote:
>>>
>>>>> We're discussing compression, which can be measured objectively -
>>>>> please don't try to divert the discussion onto the metaphysical. Show
>>>>> me compression.
>>>>
>>>>**DBTs are not metaphysical. They allow REAL differences to be heard. 
>>>>Tell
>>>>me about your experiences with DBTs between MOSFET and BJT amps.
>>>>
>>>
>>> Stop changing the subject. Either there is compression as you claim,
>>> or there is not. Show me evidence of compression.
>>
>>**I cannot. Try the test and let me know what you hear. Perhaps you will
>>have a different explanation. Negative tempco of gm is the only thing that
>>makes sense to me.
>
> We are discussing one single parameter - compression. Once you start
> with nonsense like seeing what you hear, you are no longer able to
> isolate that parameter - you hear the sum of everything. And of course
> mixed in with your "just listen" thing is all your bullshittery with
> terms like "more dynamic". This is meaningless drivel, and the
> standard recourse of the charlatan trying to claim superior skills of
> discernment to the average man. It won't wash. You made the claim, now
> substantiate it or withdraw it.

**I'm uncertain of what you are demanding I withdraw. Are you demanding that 
I withdraw my theory that pertains to why MOSFET amps sound so bad? Or are 
you demanding I withdraw what I and others hear?

Given the problems that many people hear with MOSFET amps, I proferred a 
theory. I cannot validate that theory. If you have an alternate theory to 
explain what people hear, then please present it.

As for claims of "superior skills of discernment", I make no such claims. My 
hearing is just average. Anyone with average hearing will easily discern the 
problems I speak of. I suggest you conduct your own test and confirm. 
Perhaps you will develop a more credible theory.


-- 
Trevor Wilson
www.rageaudio.com.au

"David Looser"  wrote in
message news:7lbn69F3cpcudU1@mid.individual.net
> "Trevor Wilson"  wrote
>>
>> **DBTs are not metaphysical. They allow REAL differences
>> to be heard. Tell me about your experiences with DBTs
>> between MOSFET and BJT amps.
> I'd be interested to know how these DBTs were conducted.
> How many listeners did you use?, how were they recruited,
> how much did they know about the purpose of the test? etc.

In the end you've got to go to Australia to see Trevor prove his point. I've 
been down this road with him before in his anti-loop-feedback days.

"Arny Krueger"  wrote in message 
news:C6udnefPOdIZW23XnZ2dnUVZ_hqdnZ2d@giganews.com...
> "David Looser"  wrote in
> message news:7lbn69F3cpcudU1@mid.individual.net
>> "Trevor Wilson"  wrote
>>>
>>> **DBTs are not metaphysical. They allow REAL differences
>>> to be heard. Tell me about your experiences with DBTs
>>> between MOSFET and BJT amps.
>> I'd be interested to know how these DBTs were conducted.
>> How many listeners did you use?, how were they recruited,
>> how much did they know about the purpose of the test? etc.
>
> In the end you've got to go to Australia to see Trevor prove his point. 
> I've been down this road with him before in his anti-loop-feedback days.

**Perhaps you missed my last post to you.

Here it is:

---
**I'll make it easy for you. Locate an old Phase Linear 400(b) and an early
Perreaux amp. Set up a DBT between the two and ask the listeners what
differences they feel they can hear (if any). Let me know what results you
find. Both amps are plentiful and cheap, so the test should be an easy one.
Both amps use shit-loads of global NFB, minimal bias current and primitive
topology so the only major differences are related to the output devices
used.

Take the time to listen for yourself. You might be surprised. I was.
---

Both amps were readily available in the US (and other places) and should be 
very cheap and easy to obtain. No need to travel to Australia.

-- 
Trevor Wilson
www.rageaudio.com.au

In article , David Looser
 wrote:
> "Trevor Wilson"  wrote
> >
> > **DBTs are not metaphysical. They allow REAL differences to be heard.
> > Tell me about your experiences with DBTs between MOSFET and BJT amps.
> >
> I'd be interested to know how these DBTs were conducted. How many
> listeners did you use?, how were they recruited, how much did they know
> about the purpose of the test? etc.

I'd also like to see the details of the circuits, methodology, and results.

I've often in the past compared amps made with MOSFETs with BJT. So far as
I could tell they were audibly indistinguishable provided you avoided
errors like trying to obtain power or current levels which a design could
not provide. And so far as I recall, all the published controlled tests
also show this. Certainly all the ones I've seen.

So where are the details of your DBT Trevor?

Slainte,

Jim

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

In article , Trevor Wilson
 wrote:

> "David Looser"  wrote in message
> news:7lbn69F3cpcudU1@mid.individual.net...
> > "Trevor Wilson"  wrote
> >>
> >> **DBTs are not metaphysical. They allow REAL differences to be heard.
> >> Tell me about your experiences with DBTs between MOSFET and BJT amps.
> >>
> > I'd be interested to know how these DBTs were conducted. How many
> > listeners did you use?

> **10. I arranged for a person who had no knowledge of which amp (he was
> no present at set-up time) was which to throw the switch, whilst
> keeping a record of which position the switch was in at each change. I
> set the equipment up and was present for the test, but took no part.

So the person throwing the switch did know which choice (A or B) they had
made at each time? That means the result isn't double-blind. The point of
double blind is that *noone* involved in either running or taking the test
has *any* idea which - A or B - is being presented at the time.

Where was the 'switch'?

> , how were they recruited, how much did they know about the
> > purpose of the test? etc.

> **They only knew that there might be a change in the system when the
> light changed from green to red. 

Which "light" controlled how?

> The listeners were all those who considered themselves to be
> audiophiles. They were not 'people off the street'. I was already
> familiar with the listening preferences of each. They were tested in
> groups of two, over a period of several days.

> I performed the test, because I heard about these "new" (back in the
> early 1980s) MOSFET amps and how wonderful they allegedly were. I was
> surprised at how bad they sounded, despite glowing reviews in places
> like Stereophile. I decided to recruit others to see if their
> perceptions agreed with mine. They did. All listeners reported similar
> findings. The MOSFET amps sounded 'compressed' and lacking in dynamics.

Raw data of results? Statistical analysis and outcomes in terms of levels
of confidence, etc?

Which 'amps' did you try? What were the details of the level matching,
avoidance of clipping/saturation etc?

How did you establish the results *were* a basis for conclusions about one
form of transistor versus another rather than being a problem with some
specific designs or devices?

Given all the work, where did you publish the results? Since your results
seem to run contrary to all the published results I've seen - and I suspect
would have been welcomed by many 'subjective reviewers' I would expect them
to have been eager to have them published.

The problem is that you've only now given us your selected recollections.
Not the evidence anyone else would need to see if what you say stands up as
a conclusion.

Slainte,

Jim

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

In article , Trevor Wilson
 wrote:

> --- **I'll make it easy for you. Locate an old Phase Linear 400(b) and
> an early Perreaux amp.

Your definition of "easy" seems to differ from mine. I do have new
neighbours moving in today though. Maybe they'll have the above amps to
loan me.  :-)

> Set up a DBT between the two and ask the listeners what differences they
> feel they can hear (if any). Let me know what results you find. Both
> amps are plentiful and cheap, so the test should be an easy one. Both
> amps use shit-loads of global NFB, minimal bias current and primitive
> topology so the only major differences are related to the output devices
> used.

My problem here is that in the past I *have* repeately compared amps with
different types of op devices. And heard no differences due to that when
the amps were used within their drive limits and had much the same
frequency response, etc. i.e. were sensible designs.

In addition all the properly controlled blind comparisons I've seen
published results from that could be analysed return the same result.

So if your tests show otherwise it would be important to have all the
details published for examination and consideration.

Slainte,

Jim

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

In article ,
   Trevor Wilson  wrote:
> *Depends on implementation. The MOSFETs, of course, will always sound
> like MOSFETs - dull, boring, undynamic and compressed.

I've got a pair of 150w MOSFET amps in the workshop - so listen to them
quite a lot. Actually Maplin kits, but with a rather better power supply.
And they sound as sweet as a nut.  Home made speakers too sort of thrown
together out of Audax units left over from a job. But one of those happy
coincidences that just work well.

-- 
*Don't use no double negatives *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

"Trevor Wilson"  wrote in
message news:7lc0afF3dlrfhU2@mid.individual.net
> "Arny Krueger"  wrote in message
> news:C6udnefPOdIZW23XnZ2dnUVZ_hqdnZ2d@giganews.com...
>> "David Looser"  wrote in
>> message news:7lbn69F3cpcudU1@mid.individual.net
>>> "Trevor Wilson"  wrote
>>>>
>>>> **DBTs are not metaphysical. They allow REAL
>>>> differences to be heard. Tell me about your
>>>> experiences with DBTs between MOSFET and BJT amps.
>>> I'd be interested to know how these DBTs were conducted.
>>> How many listeners did you use?, how were they
>>> recruited, how much did they know about the purpose of
>>> the test? etc.
>>
>> In the end you've got to go to Australia to see Trevor
>> prove his point. I've been down this road with him
>> before in his anti-loop-feedback days.
>
> **Perhaps you missed my last post to you.

Not at all.

Your suggest is actually less practical than me catching the next  flight to 
down under.

(True! read below!)

> Here it is:

> ---
> **I'll make it easy for you. Locate an old Phase Linear
> 400(b)

I don't have any, and don't know anybody who currently has one.

If I wanted to buy one, they seem to be going for about $500 on eBay.

>  and an early Perreaux amp.

I don't have any, and don't know anybody who even ever had  one.

I don't even know what the model number would be, since you are so vague in 
describing it.

I see that I could pick a fairly decent Perreaux amp up for $1,500 on eBay.

Northwest airlines will sell me a round trip ticket from DTW to SYD for 
$1,295.

I have proven that your suggestion is even less practical than what I first 
suggested.


> Set up a DBT between
> the two and ask the listeners what differences they feel
> they can hear (if any). Let me know what results you
> find. Both amps are plentiful and cheap, so the test
> should be an easy one. Both amps use shit-loads of global
> NFB, minimal bias current and primitive topology so the
> only major differences are related to the output devices
> used.


The real truth Trevor is that if all amplifiers sounded as different as you 
claim, there would be a world of amps that would DBT different, not just an 
early SS old-timer well-known for being a loser (whether true or not) and 
some esoteric wunder-amp.

Phil is probably right that I'll not gain much or ven anything from the 
Hitachi design I have now.
But it will always niggle at me that there maybe a better design nowadays.
MOS appeals from the robustness angle but I'm not convinced it's best for 
audio, relatively few manufacturers seem to go that route apart from in car 
audio..........
So this is my current target

http://www.tech-diy.com/Amplifiers/LM4702/LM4702_Sanken.htm

I take on board that the SAP15's may go out of exisitence in the future but 
I could always change the output stage to something else should the worst 
happen.
I even have 2 pair of SAP01M fets but looking around they don't appear to be 
stocked so they must have been a non-starter ( I got them as samples when 
they came out )

thanks for all your comments.

Pete

"Pete"

> Phil is probably right that I'll not gain much or ven anything from the 
> Hitachi design I have now.

** Huh ???

Are there posts from me here in invisible ink now  ??

Cos I cannot see what the OP is replying to.



 ....   Phil

"Phil Allison"  wrote in message 
news:7ldhf7F3dqp6sU1@mid.individual.net...
>
> "Pete"
>
>> Phil is probably right that I'll not gain much or ven anything from the 
>> Hitachi design I have now.
>
> ** Huh ???
>
> Are there posts from me here in invisible ink now  ??
>
> Cos I cannot see what the OP is replying to.
>
>
>
> ....   Phil
>
>
>
>
>
>

Phil,

Sorry, I was flicking through all the replies and took your reply a little 
out of context. There was a lot to digest ( is my excuse.....)

"** Those are Hitachi's famous TO3 pack " lateral " mosfets as used in many
famous hi-fi and professional power amps.

They are extremely easy to use, exceptionally rugged and have  NO issues
with biasing or bias stability. Plus they will share current automatically
when used in parallel."


Pete

"Pete"
> "Phil Allison"
>> "Pete"
>>
>>> Phil is probably right that I'll not gain much or ven anything from the 
>>> Hitachi design I have now.
>>
>> ** Huh ???
>>
>> Are there posts from me here in invisible ink now  ??
>>
>> Cos I cannot see what the OP is replying to.
>>
>
> Sorry, I was flicking through all the replies and took your reply a little 
> out of context. There was a lot to digest ( is my excuse.....)
>
> "** Those are Hitachi's famous TO3 pack " lateral " mosfets as used in 
> many
> famous hi-fi and professional power amps.
>
> They are extremely easy to use, exceptionally rugged and have  NO issues
> with biasing or bias stability. Plus they will share current automatically
> when used in parallel."


** Where is there any connection between my post and your comment at the top 
???

     Must be in invisible ink -  right ?



.....  Phil

"Arny Krueger"  wrote in message 
news:sPadnQEiM4oF9WzXnZ2dnUVZ_uudnZ2d@giganews.com...
> "Trevor Wilson"  wrote in
> message news:7lc0afF3dlrfhU2@mid.individual.net
>> "Arny Krueger"  wrote in message
>> news:C6udnefPOdIZW23XnZ2dnUVZ_hqdnZ2d@giganews.com...
>>> "David Looser"  wrote in
>>> message news:7lbn69F3cpcudU1@mid.individual.net
>>>> "Trevor Wilson"  wrote
>>>>>
>>>>> **DBTs are not metaphysical. They allow REAL
>>>>> differences to be heard. Tell me about your
>>>>> experiences with DBTs between MOSFET and BJT amps.
>>>> I'd be interested to know how these DBTs were conducted.
>>>> How many listeners did you use?, how were they
>>>> recruited, how much did they know about the purpose of
>>>> the test? etc.
>>>
>>> In the end you've got to go to Australia to see Trevor
>>> prove his point. I've been down this road with him
>>> before in his anti-loop-feedback days.
>>
>> **Perhaps you missed my last post to you.
>
> Not at all.
>
> Your suggest is actually less practical than me catching the next  flight 
> to down under.
>
> (True! read below!)
>
>> Here it is:
>
>> ---
>> **I'll make it easy for you. Locate an old Phase Linear
>> 400(b)
>
> I don't have any, and don't know anybody who currently has one.
>
> If I wanted to buy one, they seem to be going for about $500 on eBay.

**Sorry. It's as easy as I can make it. Old Phase Linear amps are very 
common over here. I'd assumed they'd be just as common in the US.

>
>>  and an early Perreaux amp.
>
> I don't have any, and don't know anybody who even ever had  one.
>
> I don't even know what the model number would be, since you are so vague 
> in describing it.

**Model 2150.

>
> I see that I could pick a fairly decent Perreaux amp up for $1,500 on 
> eBay.

**Given that it is a crap amp, but reliable, colour me surprised that they 
sell for so much.

>
> Northwest airlines will sell me a round trip ticket from DTW to SYD for 
> $1,295.
>
> I have proven that your suggestion is even less practical than what I 
> first suggested.

**Only for you. I provided a most economical solution.

>
>
>> Set up a DBT between
>> the two and ask the listeners what differences they feel
>> they can hear (if any). Let me know what results you
>> find. Both amps are plentiful and cheap, so the test
>> should be an easy one. Both amps use shit-loads of global
>> NFB, minimal bias current and primitive topology so the
>> only major differences are related to the output devices
>> used.
>
>
> The real truth Trevor is that if all amplifiers sounded as different as 
> you claim

**BZZZTTT! I claimed nothing of the sort. I claimed that the Phase Linear 
400(b) sounds different to a Perreaux 2150.

, there would be a world of amps that would DBT different, not just an
> early SS old-timer well-known for being a loser (whether true or not) and 
> some esoteric wunder-amp.

**We're discussing Phase Linear and Perreaux amps from the late 1970s and 
early 1980s.


-- 
Trevor Wilson
www.rageaudio.com.au

"Jim Lesurf"  wrote in message 
news:50b4d6483dnoise@audiomisc.co.uk...
> In article , Trevor Wilson
>  wrote:
>
>> "David Looser"  wrote in message
>> news:7lbn69F3cpcudU1@mid.individual.net...
>> > "Trevor Wilson"  wrote
>> >>
>> >> **DBTs are not metaphysical. They allow REAL differences to be heard.
>> >> Tell me about your experiences with DBTs between MOSFET and BJT amps.
>> >>
>> > I'd be interested to know how these DBTs were conducted. How many
>> > listeners did you use?
>
>> **10. I arranged for a person who had no knowledge of which amp (he was
>> no present at set-up time) was which to throw the switch, whilst
>> keeping a record of which position the switch was in at each change. I
>> set the equipment up and was present for the test, but took no part.
>
> So the person throwing the switch did know which choice (A or B) they had
> made at each time?

**They knew whether it was A or B, but not which amp was which.

 That means the result isn't double-blind. The point of
> double blind is that *noone* involved in either running or taking the test
> has *any* idea which - A or B - is being presented at the time.

**True enough. I never claimed that the test was perfect.

>
> Where was the 'switch'?

**In different room to the speakers systems being listened to.

>
>> , how were they recruited, how much did they know about the
>> > purpose of the test? etc.
>
>> **They only knew that there might be a change in the system when the
>> light changed from green to red.
>
> Which "light" controlled how?

**The light in the listening room.

>
>> The listeners were all those who considered themselves to be
>> audiophiles. They were not 'people off the street'. I was already
>> familiar with the listening preferences of each. They were tested in
>> groups of two, over a period of several days.
>
>> I performed the test, because I heard about these "new" (back in the
>> early 1980s) MOSFET amps and how wonderful they allegedly were. I was
>> surprised at how bad they sounded, despite glowing reviews in places
>> like Stereophile. I decided to recruit others to see if their
>> perceptions agreed with mine. They did. All listeners reported similar
>> findings. The MOSFET amps sounded 'compressed' and lacking in dynamics.
>
> Raw data of results?

**Lost in the mists of time. The results were 100% anyway.

 Statistical analysis and outcomes in terms of levels
> of confidence, etc?

**The participants picked which amp was playing 100% of the time.

>
> Which 'amps' did you try?

**Phase Linear 400(b) and Perreaux 2150.

 What were the details of the level matching,
> avoidance of clipping/saturation etc?

**I installed level pots in each amp and matched levels to within 0.1dB or 
better. Prior to the testing, I used my CRO (Tek 465b) to ensure that the 
amps never reached Voltage limiting with the music used for the test. The 
main volume control was marked with a line and instructions that it always 
remain below that line (Voltage limiting). In my prior testing, I found that 
normal listening levels rarely exceeded 15 - 16 Volts RMS.

>
> How did you establish the results *were* a basis for conclusions about one
> form of transistor versus another rather than being a problem with some
> specific designs or devices?

**I didn't, though I've noted (informally) that most (all?) Class A/B MOSFET 
amps exhibit similar sonic issues to those I heard several decades ago.

>
> Given all the work, where did you publish the results?

**It was for me and to prove a point to some of my sceptical clients. As you 
have already discovered, the test was hardly rigorous enough to publish.

 Since your results
> seem to run contrary to all the published results I've seen

**Do they? Can you cite where a DBT was performed using a Phase Linear vs. a 
Perreaux?

 - and I suspect
> would have been welcomed by many 'subjective reviewers' I would expect 
> them
> to have been eager to have them published.

**Subjective reviewers tend to avoid DBTs.

>
> The problem is that you've only now given us your selected recollections.
> Not the evidence anyone else would need to see if what you say stands up 
> as
> a conclusion.

**Indeed. Perhaps you may care to relicate my test?


-- 
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson"  wrote
>
> **We're discussing Phase Linear and Perreaux amps from the late 1970s and 
> early 1980s.
>

OK, good. So this is nothing to do with MOSFETS in general, merely one 
particular rather ancient amplifier. Glad we got that clarified.

David.

"Trevor Wilson"  wrote
>>
>>> **They only knew that there might be a change in the system when the
>>> light changed from green to red.
>>
>> Which "light" controlled how?
>
> **The light in the listening room.
>

Why a light? It's existence reduces the validity of your results. The 
listeners should not only not know which amp is 'A' and which 'B'. They 
should not know whether, at any given time, they are listening to 'A' or 
'B'. Listeners will often give a preference when asked to compare 'A' to 'A' 
or 'B' to 'B' because they think there *ought* to be a difference! Ideally 
they should not even know that the test is a comparative test of amps 
(rather than say sources or cables).

David.

"Phil Allison"  wrote in message 
news:7leinaF3d1k76U1@mid.individual.net...
>
> "Pete"
>> "Phil Allison"
>>> "Pete"
>>>
>>>> Phil is probably right that I'll not gain much or ven anything from the 
>>>> Hitachi design I have now.
>>>
>>> ** Huh ???
>>>
>>> Are there posts from me here in invisible ink now  ??
>>>
>>> Cos I cannot see what the OP is replying to.
>>>
>>
>> Sorry, I was flicking through all the replies and took your reply a 
>> little out of context. There was a lot to digest ( is my excuse.....)
>>
>> "** Those are Hitachi's famous TO3 pack " lateral " mosfets as used in 
>> many
>> famous hi-fi and professional power amps.
>>
>> They are extremely easy to use, exceptionally rugged and have  NO issues
>> with biasing or bias stability. Plus they will share current 
>> automatically
>> when used in parallel."
>
>
> ** Where is there any connection between my post and your comment at the 
> top ???
>
>     Must be in invisible ink -  right ?
>
>
>
> .....  Phil
>
>

OK Phil, no connection, sorry.

I have re-read the posts and it was Woody who said

"Why bother? The basic Hitachi design is as good as it gets. You can improve 
things by building a proper regulated power supply for it."

Pete

In article , David Looser
 wrote:
> "Trevor Wilson"  wrote
> >
> > **We're discussing Phase Linear and Perreaux amps from the late 1970s
> > and early 1980s.
> >

> OK, good. So this is nothing to do with MOSFETS in general, merely one
> particular rather ancient amplifier. Glad we got that clarified.

Yes. If that is the case then it makes more sense to me since I have also
encountered some amps that 'sounded different' because they had some flaw
or limitation in the design. Given some of the weirder designs that are
sold to 'audiophiles' I find it quite plausible. But it may tell us nothing
about MOSFET vs Bipolar as classes when used appropriately within their
limits.

Slainte,

Jim

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

In article , Trevor Wilson
 wrote:

> "Jim Lesurf"  wrote in message
> news:50b4d6483dnoise@audiomisc.co.uk...
> > In article , Trevor Wilson

> >
> > So the person throwing the switch did know which choice (A or B) they
> > had made at each time?

> **They knew whether it was A or B, but not which amp was which.

>  That means the result isn't double-blind. The point of
> > double blind is that *noone* involved in either running or taking the
> > test has *any* idea which - A or B - is being presented at the time.

> **True enough. I never claimed that the test was perfect.

But the above means that the test can't be established as blind. So the
results could easily be for reasons other than the one you asserted. i.e.
nothing to do with 'MOSFET' being any different to 'Bipolar' as classes of
o/p device. Thus your evidence isn't reliable as a basis for your belief.

> >
> > Where was the 'switch'?

> **In different room to the speakers systems being listened to.

No. I meant where in the experimental system?

> >
> >> , how were they recruited, how much did they know about the
> >> > purpose of the test? etc.
> >
> >> **They only knew that there might be a change in the system when the
> >> light changed from green to red.
> >
> > Which "light" controlled how?

> **The light in the listening room.

Controlled *how*?

> > Raw data of results?

> **Lost in the mists of time. The results were 100% anyway.

That has no assessable meaning without knowing how many times the test was
done, if the same material was used, conditions of tests, etc, etc.

>  Statistical analysis and outcomes in terms of levels
> > of confidence, etc?

> **The participants picked which amp was playing 100% of the time.

Problems as above.

I could easily say "I spent 2 mins listening to one amp, then 1 min
listening to another. I could hear they were different. 100% right." Alas,
as evidence that would be worthless.

Are you not aware of the various proceedural and other flaws that can spoil
a test even when 'blind'? e.g. the flaws with the Stereophile tests they
did at a show some years ago?

> >
> > Which 'amps' did you try?

> **Phase Linear 400(b) and Perreaux 2150.

>  What were the details of the level matching,
> > avoidance of clipping/saturation etc?

> **I installed level pots in each amp and matched levels to within 0.1dB
> or better. Prior to the testing, I used my CRO (Tek 465b) to ensure
> that the amps never reached Voltage limiting with the music used for
> the test. The main volume control was marked with a line and
> instructions that it always remain below that line (Voltage limiting).
> In my prior testing, I found that normal listening levels rarely
> exceeded 15 - 16 Volts RMS.

How did you establish that *current* limiting never occurred? My experience
with o/p fets from days of yore is that they were far more prone to this
than bipolars.

How did you monitor for any current limiting or clipping *during the
tests*? The problem here is that real-world speakers can be more demanding
of current that you might be aware when playing music.

> >
> > How did you establish the results *were* a basis for conclusions about
> > one form of transistor versus another rather than being a problem with
> > some specific designs or devices?

> **I didn't, though I've noted (informally) that most (all?) Class A/B
> MOSFET amps exhibit similar sonic issues to those I heard several
> decades ago.

Afraid that is an opinion, not assessable evidence.

> >
> > Given all the work, where did you publish the results?

> **It was for me and to prove a point to some of my sceptical clients. As
> you have already discovered, the test was hardly rigorous enough to
> publish.

>  Since your results
> > seem to run contrary to all the published results I've seen

> **Do they? Can you cite where a DBT was performed using a Phase Linear
> vs. a Perreaux?

Sorry. I thought you were claiming that *MOSFETS* sounded different as a
class of device to *Bipolars*. Are you now *only* saying that the Phase
Linear sounded different to 'a Perraux'? 

So are you making no claim wrt this being a general result for the two
types of output device regardless of the choice of individual device type
or circuitry?

>  - and I suspect
> > would have been welcomed by many 'subjective reviewers' I would expect
> > them to have been eager to have them published.

> **Subjective reviewers tend to avoid DBTs.

I wonder why?  :-)

> >
> > The problem is that you've only now given us your selected
> > recollections. Not the evidence anyone else would need to see if what
> > you say stands up as a conclusion.

> **Indeed. Perhaps you may care to relicate my test?

You are offering to send me a Phase Linear and 'a Perraux' so I can do this
with no costs to myself?

If so, then I still would have some problems. One is that I can't
'replication your test' because you haven't actually defined all that was
involved and given me your raw data, etc so I could see if I could either
match what you did, or spot any flaws that would make a repeat pointless.
If I did the test differently, then I might not replicate your results for
that (unknown) reason.

Or are you asking me to (again) compare different amps using a better
defined method which might differ from the one you used?

If the latter, it is something I have done many times in past decades. The
results in general were that neither I - nor others I tried them on - could
relaibly tell one amp from another. i.e. they/I showed no ability to do so
with statistical reliability.

Only exceptions were when there was a measureable difference like one amp
was clipping/saturating  or the gain levels or frequency response were
sufficiently different. 

Yes, I did experiment with MOSFET amps. I found they worked OK provided you
could ensure the circuit drove them without allowing RF bursts, and you
kept within their limited current range. I preferred bipolars because I
personally found them easy to use, and they could provide large peak
currents, etc. So seemed to me more suited to real music.

And I'm afraid that these days I don't think it would be fair to do such a
test simply using my own ears. Afraid I am now too old for that to be
reliable. So I'd need to line up a set of listeners generally younger and
more alert than myself. Would you be paying for any of this?

Slainte,

Jim

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

"Jim Lesurf"  wrote in message
news:50b55e199fnoise@audiomisc.co.uk
> In article , David
> Looser  wrote:
>> "Trevor Wilson"  wrote
>>>
>>> **We're discussing Phase Linear and Perreaux amps from
>>> the late 1970s and early 1980s.

>> OK, good. So this is nothing to do with MOSFETS in
>> general, merely one particular rather ancient amplifier.
>> Glad we got that clarified.

IOW, it is essentially OT to the OP and most of the discussion that followed 
it.

> Yes. If that is the case then it makes more sense to me
> since I have also encountered some amps that 'sounded
> different' because they had some flaw or limitation in
> the design.

However, there's no reliable evidence that the amps that Trevor mentioned 
have this kind of flaw.

So Trevor's proposed test is doubly irrelevant. It's not about the kind of 
amps that this thread was created to discuss, and there's no reliable 
evidence that the amps he mentioned actually have audible design flaws as 
typically used.

>  Given some of the weirder designs that are
> sold to 'audiophiles' I find it quite plausible.

Aside from that, there is a lot of audiophile lore and legend about certain 
amps always sounding bad, when said amps in good operating condition 
actually sound OK.  Any amp that was sold in large volumes and may have been 
prone to failure might be getting this kind of treatment. This is especially 
true if the amp  has a common failure mode that does not completely disable 
it.

> But it
> may tell us nothing about MOSFET vs Bipolar as classes
> when used appropriately within their limits.

Exactly. My audio club has examined this issue in some depth and no 
surprise, we found that a properly-designed amp in good operating condition 
sounds great, no matter which type of output device is used.

There is a precident for this. There was a class of SS output device that 
was widely used and has completely fallen into complete disuse. But, that 
did not happen to either MOSFET or Bipolar technology.  I suspect that if 
marketing stats were avaialble we'd find that there was a time when MOSFET 
usage increased dramatically and obtained a fair market share. Since then, 
MOSFET use has probably decreased, but there is still significant use of it.

The engineers I talk to say that linear (not switchmode) MOSFET amps tend to 
be more costly and less efficient for a given power and performance level. 
Note that a long-time advocate of FET power amps for audio, namely Hafler is 
no longer in production. Haflers had a reputation for sounding great but 
being costly and inefficient. Not all that inefficient, but audio can be a 
very competitive business.

"Pete" 
>
>> ** Where is there any connection between my post and your comment at the 
>> top ???
>>
>>    Must be in invisible ink -  right ?
>>
> OK Phil, no connection, sorry.
>
> I have re-read the posts and it was Woody who said ...
>

** Apology accepted.

Basic usenet etiquette requires you ALWAYS  post  UNDER any words you are 
referring to.

There is  BLOODY SIMPLE   reason for that   !!!!

Capice ???????



....   Phil

"Jim Lesurf"  wrote in message 
news:50b55dcda4noise@audiomisc.co.uk...
> In article , Trevor Wilson
>  wrote:
>
>> "Jim Lesurf"  wrote in message
>> news:50b4d6483dnoise@audiomisc.co.uk...
>> > In article , Trevor Wilson
>
>> >
>> > So the person throwing the switch did know which choice (A or B) they
>> > had made at each time?
>
>> **They knew whether it was A or B, but not which amp was which.
>
>>  That means the result isn't double-blind. The point of
>> > double blind is that *noone* involved in either running or taking the
>> > test has *any* idea which - A or B - is being presented at the time.
>
>> **True enough. I never claimed that the test was perfect.
>
> But the above means that the test can't be established as blind.

**Like I said: It was not a perfect test.

 So the
> results could easily be for reasons other than the one you asserted. i.e.
> nothing to do with 'MOSFET' being any different to 'Bipolar' as classes of
> o/p device. Thus your evidence isn't reliable as a basis for your belief.

**It is not a belief. The test was constructed in an attempt to verify what 
I and others had already informally noted as having heard.

>
>> >
>> > Where was the 'switch'?
>
>> **In different room to the speakers systems being listened to.
>
> No. I meant where in the experimental system?

**At the speaker terminals of the amplifiers. The switches were relays.

>
>> >
>> >> , how were they recruited, how much did they know about the
>> >> > purpose of the test? etc.
>> >
>> >> **They only knew that there might be a change in the system when the
>> >> light changed from green to red.
>> >
>> > Which "light" controlled how?
>
>> **The light in the listening room.
>
> Controlled *how*?

**By the person throwing the switch. He also controlled the lights. The 
lights merely indicated a POSSIBLE change in amplifier.

>
>> > Raw data of results?
>
>> **Lost in the mists of time. The results were 100% anyway.
>
> That has no assessable meaning without knowing how many times the test was
> done, if the same material was used, conditions of tests, etc, etc.

**I understand and have acknowledged the imperfect nature of the test.

>
>>  Statistical analysis and outcomes in terms of levels
>> > of confidence, etc?
>
>> **The participants picked which amp was playing 100% of the time.
>
> Problems as above.
>
> I could easily say "I spent 2 mins listening to one amp, then 1 min
> listening to another. I could hear they were different. 100% right." Alas,
> as evidence that would be worthless.

**Indeed. Except that the listeners were able to correctly identify each 
amplifier perfectly.

>
> Are you not aware of the various proceedural and other flaws that can 
> spoil
> a test even when 'blind'? e.g. the flaws with the Stereophile tests they
> did at a show some years ago?

**I am now, but was not then. If I were to perform a similar test today, I 
would certainly be doing things very differently.

>
>> >
>> > Which 'amps' did you try?
>
>> **Phase Linear 400(b) and Perreaux 2150.
>
>>  What were the details of the level matching,
>> > avoidance of clipping/saturation etc?
>
>> **I installed level pots in each amp and matched levels to within 0.1dB
>> or better. Prior to the testing, I used my CRO (Tek 465b) to ensure
>> that the amps never reached Voltage limiting with the music used for
>> the test. The main volume control was marked with a line and
>> instructions that it always remain below that line (Voltage limiting).
>> In my prior testing, I found that normal listening levels rarely
>> exceeded 15 - 16 Volts RMS.
>
> How did you establish that *current* limiting never occurred?

**I didn't. In fact, when using the Quad ESL63 speakers (I also used KEF 
104.2 speakers), I suspect that both amps would have experienced current 
limiting at some point.

 My experience
> with o/p fets from days of yore is that they were far more prone to this
> than bipolars.

**Indeed. However, the current limiting of MOSFETs has always tended to be 
more benign than BJTs (depending on how the BJT current limiting is 
employed).

>
> How did you monitor for any current limiting or clipping *during the
> tests*?

**No. As I previously stated though, I checked the music, prior to the test 
with my CRO and did not note any significant issues. Yes, I am well aware of 
how transient the nature of current limiting can be and, thus how current 
limiting could have occured.

 The problem here is that real-world speakers can be more demanding
> of current that you might be aware when playing music.

**Indeed. OTOH, the KEFs were chosen for a couple of reasons. One is the 
extensive use of Zobels throughout the crossover and the consequently 
relatively smooth 4 Ohm load presented. The ESL63 was not as easy to drive. 
In fact, the differences between the two amps was far more profound with the 
Quads, than with the KEFs.

>
>> >
>> > How did you establish the results *were* a basis for conclusions about
>> > one form of transistor versus another rather than being a problem with
>> > some specific designs or devices?
>
>> **I didn't, though I've noted (informally) that most (all?) Class A/B
>> MOSFET amps exhibit similar sonic issues to those I heard several
>> decades ago.
>
> Afraid that is an opinion, not assessable evidence.

**Indeed. Hence the inclusion of the word: "informally".

>
>> >
>> > Given all the work, where did you publish the results?
>
>> **It was for me and to prove a point to some of my sceptical clients. As
>> you have already discovered, the test was hardly rigorous enough to
>> publish.
>
>>  Since your results
>> > seem to run contrary to all the published results I've seen
>
>> **Do they? Can you cite where a DBT was performed using a Phase Linear
>> vs. a Perreaux?
>
> Sorry. I thought you were claiming that *MOSFETS* sounded different as a
> class of device to *Bipolars*. Are you now *only* saying that the Phase
> Linear sounded different to 'a Perraux'?

**Nope. Those are the two amps I tested. I have not performed any tests 
since. All listening has been done on a much more informal basis.

>
> So are you making no claim wrt this being a general result for the two
> types of output device regardless of the choice of individual device type
> or circuitry?

**The measured performance of both amplifiers significantly exceeded the 
limits of human hearing WRT frequency response, THD, IMD et al. Both amps 
had roughly similar power output capability. Certainly, the topology of both 
amps is somewhat different, but the big differences lie in the use of 
different technology output devices.


>
>>  - and I suspect
>> > would have been welcomed by many 'subjective reviewers' I would expect
>> > them to have been eager to have them published.
>
>> **Subjective reviewers tend to avoid DBTs.
>
> I wonder why?  :-)
>
>> >
>> > The problem is that you've only now given us your selected
>> > recollections. Not the evidence anyone else would need to see if what
>> > you say stands up as a conclusion.
>
>> **Indeed. Perhaps you may care to relicate my test?
>
> You are offering to send me a Phase Linear and 'a Perraux' so I can do 
> this
> with no costs to myself?

**Nope. Both amps are common and cheap.

>
> If so, then I still would have some problems. One is that I can't
> 'replication your test' because you haven't actually defined all that was
> involved and given me your raw data, etc so I could see if I could either
> match what you did, or spot any flaws that would make a repeat pointless.
> If I did the test differently, then I might not replicate your results for
> that (unknown) reason.

**Fair enough.

>
> Or are you asking me to (again) compare different amps using a better
> defined method which might differ from the one you used?

**That would be a possibility. If you feel that it might be constructive to 
do so.


>
> If the latter, it is something I have done many times in past decades. The
> results in general were that neither I - nor others I tried them on - 
> could
> relaibly tell one amp from another. i.e. they/I showed no ability to do so
> with statistical reliability.

**You have directly compared Class A/B MOSFET amps with Class A/B BJT amps?

>
> Only exceptions were when there was a measureable difference like one amp
> was clipping/saturating  or the gain levels or frequency response were
> sufficiently different.

**Sure.

>
> Yes, I did experiment with MOSFET amps. I found they worked OK provided 
> you
> could ensure the circuit drove them without allowing RF bursts, and you
> kept within their limited current range. I preferred bipolars because I
> personally found them easy to use, and they could provide large peak
> currents, etc. So seemed to me more suited to real music.

**Indeed. In the early days, BJTs provided significantly more current for 
much less money. Not so much today. MOSFETs capable of delivery large 
currents are relatively cheap.

>
> And I'm afraid that these days I don't think it would be fair to do such a
> test simply using my own ears. Afraid I am now too old for that to be
> reliable. So I'd need to line up a set of listeners generally younger and
> more alert than myself. Would you be paying for any of this?

**Not a chance. If you are sufficiently motivated you will do what I did. If 
you are not, then you won't.


-- 
Trevor Wilson
www.rageaudio.com.au

In article , Trevor Wilson
 wrote:

> "Jim Lesurf"  wrote in message
> news:50b55dcda4noise@audiomisc.co.uk...
> > In article , Trevor Wilson
> >  wrote:
> >
> >> "Jim Lesurf"  wrote in message
> >> news:50b4d6483dnoise@audiomisc.co.uk...
> >> > In article , Trevor Wilson
> >
> >> >
> >> > So the person throwing the switch did know which choice (A or B)
> >> > they had made at each time?
> >
> >> **They knew whether it was A or B, but not which amp was which.
> >
> >>  That means the result isn't double-blind. The point of
> >> > double blind is that *noone* involved in either running or taking
> >> > the test has *any* idea which - A or B - is being presented at the
> >> > time.
> >
> >> **True enough. I never claimed that the test was perfect.
> >
> > But the above means that the test can't be established as blind.

> **Like I said: It was not a perfect test.

That does seem rather an understatement. Given that your answers indicate
that the test may well have been worthless, certainly so as evidence for a
claim that - as a class of devices - MOSFETs and BJTs 'sound different'.



>  So the
> > results could easily be for reasons other than the one you asserted.
> > i.e. nothing to do with 'MOSFET' being any different to 'Bipolar' as
> > classes of o/p device. Thus your evidence isn't reliable as a basis
> > for your belief.

> **It is not a belief. 

I'm afraid that simply re-asserting a belief does not make that belief
correct as a description of reality.

> The test was constructed in an attempt to verify
> what I and others had already informally noted as having heard.

But from your own answers since, clearly cannot have done that if what you
wished to verify was if MOSFETs and BJTs sounded different as a class of
devices. So by your own comments since, the test results were worthless for
that purpose.

> >> >
> >> >> , how were they recruited, how much did they know about the
> >> >> > purpose of the test? etc.
> >> >
> >> >> **They only knew that there might be a change in the system when
> >> >> the light changed from green to red.
> >> >
> >> > Which "light" controlled how?
> >
> >> **The light in the listening room.
> >
> > Controlled *how*?

> **By the person throwing the switch. He also controlled the lights. The
> lights merely indicated a POSSIBLE change in amplifier.

So they also operated this light as often when there was no change as when
there was? To have not done so would be a methodological flaw unless you
dealt with established 'difference' bias in some other way. cf the
Stereophile test that fell foul of this problem and thus produced a false
claim about amps being shown to sound different.

> >
> >> > Raw data of results?
> >
> >> **Lost in the mists of time. The results were 100% anyway.
> >
> > That has no assessable meaning without knowing how many times the test
> > was done, if the same material was used, conditions of tests, etc, etc.

> **I understand and have acknowledged the imperfect nature of the test.

But not that the results are actually of no worth in supporting the view
you initially expressed re MOSFET versus BJT.


> >
> >>  Statistical analysis and outcomes in terms of levels
> >> > of confidence, etc?
> >
> >> **The participants picked which amp was playing 100% of the time.
> >
> > Problems as above.
> >
> > I could easily say "I spent 2 mins listening to one amp, then 1 min
> > listening to another. I could hear they were different. 100% right."
> > Alas, as evidence that would be worthless.

> **Indeed. Except that the listeners were able to correctly identify each
> amplifier perfectly.

Which is meanignless in this case for the purposes of your initial claim.

> >
> > How did you establish that *current* limiting never occurred?

> **I didn't. In fact, when using the Quad ESL63 speakers (I also used KEF
> 104.2 speakers), I suspect that both amps would have experienced
> current limiting at some point.

In that case any difference could quite easily come from differences in the
current limiting behaviours of the two specific designs using the specific
devices. Nothing to do with MOSFET versus BJT as a class of device.

>  My experience
> > with o/p fets from days of yore is that they were far more prone to
> > this than bipolars.

> **Indeed. However, the current limiting of MOSFETs has always tended to
> be more benign than BJTs (depending on how the BJT current limiting is
> employed).

That depends on how you define 'benign'. I define it as being 'never
happens in the normal use because the saturation level is above the peak
demanded'. You may be defining it to mean 'don't blow up the amplifier'.
But I take that as a safety requirement.  :-)

In the above context I regard BJT behaviour as more 'benign' for music as
the devices tend to allow very high peak currents *without* saturation or
failure. Whereas FETs tend to dumbly limit at a specified level, for peaks
or for continuous. That is OK for test sinewaves, but not ideal for music.

> >
> > How did you monitor for any current limiting or clipping *during the
> > tests*?

> **No. As I previously stated though, I checked the music, prior to the
> test with my CRO and did not note any significant issues. Yes, I am
> well aware of how transient the nature of current limiting can be and,
> thus how current limiting could have occured.

Thus meaning your test can't support the original claim you made.

>  The problem here is that real-world speakers can be more demanding
> > of current that you might be aware when playing music.

> **Indeed. OTOH, the KEFs were chosen for a couple of reasons. One is the
> extensive use of Zobels throughout the crossover and the consequently
> relatively smooth 4 Ohm load presented. The ESL63 was not as easy to
> drive. In fact, the differences between the two amps was far more
> profound with the Quads, than with the KEFs.

If so, that supports what I am saying.

> >
> >> >
> >> > How did you establish the results *were* a basis for conclusions
> >> > about one form of transistor versus another rather than being a
> >> > problem with some specific designs or devices?
> >
> >> **I didn't, though I've noted (informally) that most (all?) Class A/B
> >> MOSFET amps exhibit similar sonic issues to those I heard several
> >> decades ago.
> >
> > Afraid that is an opinion, not assessable evidence.

> **Indeed. Hence the inclusion of the word: "informally".

And means you can't then quote the results to try and use them to support
your beliefs when making claims about them to other people. As you seem to
have been doing...  :-)

> >
> >> >
> >> > Given all the work, where did you publish the results?
> >
> >> **It was for me and to prove a point to some of my sceptical clients.
> >> As you have already discovered, the test was hardly rigorous enough
> >> to publish.
> >
> >>  Since your results
> >> > seem to run contrary to all the published results I've seen
> >
> >> **Do they? Can you cite where a DBT was performed using a Phase
> >> Linear vs. a Perreaux?
> >
> > Sorry. I thought you were claiming that *MOSFETS* sounded different as
> > a class of device to *Bipolars*. Are you now *only* saying that the
> > Phase Linear sounded different to 'a Perraux'?

> **Nope. Those are the two amps I tested. I have not performed any tests
> since. All listening has been done on a much more informal basis.

So your claim now is simply about those two amps? Any previous statements
you made should not now be taken to mean you are claiming that MOSFETs
sound any different to BJTs as classes of device?

> >
> >> **Indeed. Perhaps you may care to relicate my test?
> >
> > You are offering to send me a Phase Linear and 'a Perraux' so I can do
> > this with no costs to myself?

> **Nope. Both amps are common and cheap.

Which should make it cheap and easy for you to obtain them for me.

Afraid I can't recall the last time I saw either amp. Indeed the name
'Perraux' does not mean anything to me as I can't recall an amp of that
name at present.

If they are so cheap, would you pay the price if I found one of each amp
and told you the asking prices? You are probably safe here as I suspect
no-one in the UK will have both amps for sale at any price!



> >
> > If the latter, it is something I have done many times in past decades.
> > The results in general were that neither I - nor others I tried them
> > on - could relaibly tell one amp from another. i.e. they/I showed no
> > ability to do so with statistical reliability.

> **You have directly compared Class A/B MOSFET amps with Class A/B BJT
> amps?

Yes. I repreatedly did that in the past. Remember I was involved in
developing a new amp back in the late 1970s and early 1980s. As part of
that I both 'borrowed' a range of designs from others and built a number of
them myself. Then tested them in listening comparisons as well as on a test
bench. At that time Hitachi and others were bringing in their new FET
designs.

During the late 1980s and into the 1990s I also did some similar things
with a few friends, one of whom is actually a very good amp designer in my
view.

The results were as I have said. That provided we avoided simply and
obvious problems like level mismatch, gross distortions, ensured stability,
avoided clipping or saturation, etc, the amps gave no reliable sign of
producing audible differences.

But then we were careful to allow for the way many other factors can affect
perception. So avoided trying to jump to conclusions.

And as I have said, all the well-performed comparisons I've seen reported
come to the same conclusion.

Some reports initially concluded otherwise - e.g, the Stereophile test. But
when examined the results turn out not to reliably do what was initially
believed.

> >
> > And I'm afraid that these days I don't think it would be fair to do
> > such a test simply using my own ears. Afraid I am now too old for that
> > to be reliable. So I'd need to line up a set of listeners generally
> > younger and more alert than myself. Would you be paying for any of
> > this?

> **Not a chance. If you are sufficiently motivated you will do what I
> did. If you are not, then you won't.

I see no reason to bother at the moment since you haven't actually provided
any evidence that you *did* hear a difference due to MOSFET versus BJT as a
class of device. Instead you may simply have found that currently limiting
can be audible. Which does not surprise me as it agrees with my own
experience and would be so for perfectly understandable reasons.  :-)

But if you can find an ultra-cheap pair of the amps you used and are
willing to buy them, I'd enjoy trying them. If only to measure the current
limiting behaviours.  :-)

Slainte,

Jim

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

Jim Lesurf  wrote:

> In article , Trevor Wilson
>  wrote:

[snip - Phase Linear v Preeeaux]

> > **Nope. Both amps are common and cheap.
> 
> Which should make it cheap and easy for you to obtain them for me.
> 
> Afraid I can't recall the last time I saw either amp. Indeed the name
> 'Perraux' does not mean anything to me as I can't recall an amp of that
> name at present.

http://www.perreaux.com in New Zealand. Expensive!!

http://uk.cinenow.com/articles/9440-perreauxs-new-250i-class-ab-intergrated-amp

-- 
David Pitt
Snow Leopard - MessengerPro

In article , David Pitt
 wrote:
> Jim Lesurf  wrote:

> > In article , Trevor Wilson
> >  wrote:

> [snip - Phase Linear v Preeeaux]

> > > **Nope. Both amps are common and cheap.
> > 
> > Which should make it cheap and easy for you to obtain them for me.
> > 
> > Afraid I can't recall the last time I saw either amp. Indeed the name
> > 'Perraux' does not mean anything to me as I can't recall an amp of
> > that name at present.

> http://www.perreaux.com in New Zealand. Expensive!!

So despite what Trevor said, neither common (I can't recall ever
encountering one in the UK) nor cheap.

Oh well, if Trevor wants to buy me one for Xmas I can then give it a listen
and see if it justifies his claim that it isn't worth using.  :-)

Slainte,

Jim

> http://uk.cinenow.com/articles/9440-perreauxs-new-250i-class-ab-intergrated-amp

-- 
Please use the address on the audiomisc page if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

Jim Lesurf  wrote:

> In article , David Pitt
>  wrote:
> > Jim Lesurf  wrote:
> 
> > > In article , Trevor Wilson
> > >  wrote:
> 
> > [snip - Phase Linear v Perreaux]
> 
> > > > **Nope. Both amps are common and cheap.
> > > 
> > > Which should make it cheap and easy for you to obtain them for me.
> > > 
> > > Afraid I can't recall the last time I saw either amp. Indeed the name
> > > 'Perraux' does not mean anything to me as I can't recall an amp of
> > > that name at present.
> 
> > http://www.perreaux.com in New Zealand. Expensive!!
> 
> So despite what Trevor said, neither common (I can't recall ever
> encountering one in the UK) nor cheap.

Perreaux kit may be cheap and common in Australia, where Trevor is. From the
Perreaux site the éloquence range, which uses MOSFET output devices, give an
output that is "dynamic, commanding and resolute". Trevor would disagree
with that first term.   


-- 
David Pitt
Snow Leopard - MessengerPro

On 3 Nov, 23:27, "Trevor Wilson" 
wrote:
> "Don Pearce"  wrote in message
>
> news:4af5af9a.41203046@news.eternal-september.org...
>
>
>
>
>
> > On Wed, 4 Nov 2009 09:12:59 흝, "Trevor Wilson"
> >  wrote:
>
> >>"Don Pearce"  wrote in message
> >>news:4af4a78e.39143906@news.eternal-september.org...
> >>> On Wed, 4 Nov 2009 08:47:13 흝, "Trevor Wilson"
> >>>  wrote:
>
> >>>>> We're discussing compression, which can be measured objectively -
> >>>>> please don't try to divert the discussion onto the metaphysical. Show
> >>>>> me compression.
>
> >>>>**DBTs are not metaphysical. They allow REAL differences to be heard.
> >>>>Tell
> >>>>me about your experiences with DBTs between MOSFET and BJT amps.
>
> >>> Stop changing the subject. Either there is compression as you claim,
> >>> or there is not. Show me evidence of compression.
>
> >>**I cannot. Try the test and let me know what you hear. Perhaps you will
> >>have a different explanation. Negative tempco of gm is the only thing that
> >>makes sense to me.
>
> > We are discussing one single parameter - compression. Once you start
> > with nonsense like seeing what you hear, you are no longer able to
> > isolate that parameter - you hear the sum of everything. And of course
> > mixed in with your "just listen" thing is all your bullshittery with
> > terms like "more dynamic". This is meaningless drivel, and the
> > standard recourse of the charlatan trying to claim superior skills of
> > discernment to the average man. It won't wash. You made the claim, now
> > substantiate it or withdraw it.
>
> **I'm uncertain of what you are demanding I withdraw. Are you demanding that
> I withdraw my theory that pertains to why MOSFET amps sound so bad? Or are
> you demanding I withdraw what I and others hear?
>
> Given the problems that many people hear with MOSFET amps, I proferred a
> theory. I cannot validate that theory. If you have an alternate theory to
> explain what people hear, then please present it.
>
> As for claims of "superior skills of discernment", I make no such claims. My
> hearing is just average. Anyone with average hearing will easily discern the
> problems I speak of. I suggest you conduct your own test and confirm.
> Perhaps you will develop a more credible theory.
>
> --
> Trevor Wilsonwww.rageaudio.com.au- Hide quoted text -
>
> - Show quoted text -

More OSAF nonsense from Trevor. People do not hear 'problems' with
MOSFET (or any other properly functioning) amplifiers, they all sound
the same unless clipping. I still have on the cards an offer of £1,000
to anyone who can hear differences among amplifiers or cables under
level-matched DBT conditions. No one has even *tried* in the more than
ten years this offer has been on the table. I've tried it myself -
which is the point at which I stopped building amps and just bought
the cheapest that would drive my speakers properly. I still have my
trusty pure Class A Krell as a reference, but lots of others to which
I have *carefully* compared it sound exactly the same when driving
lighter speaker loads than my Apogees.

"Audionut"  wrote


Audionut?

<snip Trevor's silly *opinionating*>


More OSAF nonsense from Trevor. People do not hear 'problems' with
MOSFET (or any other properly functioning) amplifiers, they all sound
the same unless clipping. I still have on the cards an offer of £1,000
to anyone who can hear differences among amplifiers or cables under
level-matched DBT conditions. No one has even *tried* in the more than
ten years this offer has been on the table. I've tried it myself -
which is the point at which I stopped building amps and just bought
the cheapest that would drive my speakers properly. I still have my
trusty pure Class A Krell as a reference, but lots of others to which
I have *carefully* compared it sound exactly the same when driving
lighter speaker loads than my Apogees.



Fuck! I've *conjured up* Pinky by mentioning him!!

How about if I mention Trotsky - I wonder what he's doing these days? Coupla 
dozen more 'names from the past' and this place'll be just like old times!! 
(Then I'll *definitely* have to bugger off! :-)


Anyway, you're going to have to up your £1,000 challenge, Pinkus - it's 
starting to look like Dr Evil holding the world to ransom for....

< little finger in corner of mouth >

....**A MILLION DOLLARS**...!!

:-)

"Audionut"  wrote in message 
news:b600e54d-1031-4f5d-937c-c8e929124d37@v25g2000yqk.googlegroups.com...
On 3 Nov, 23:27, "Trevor Wilson" 
wrote:
> "Don Pearce"  wrote in message
>
> news:4af5af9a.41203046@news.eternal-september.org...
>
>
>
>
>
> > On Wed, 4 Nov 2009 09:12:59 +1100, "Trevor Wilson"
> >  wrote:
>
> >>"Don Pearce"  wrote in message
> >>news:4af4a78e.39143906@news.eternal-september.org...
> >>> On Wed, 4 Nov 2009 08:47:13 +1100, "Trevor Wilson"
> >>>  wrote:
>
> >>>>> We're discussing compression, which can be measured objectively -
> >>>>> please don't try to divert the discussion onto the metaphysical. 
> >>>>> Show
> >>>>> me compression.
>
> >>>>**DBTs are not metaphysical. They allow REAL differences to be heard.
> >>>>Tell
> >>>>me about your experiences with DBTs between MOSFET and BJT amps.
>
> >>> Stop changing the subject. Either there is compression as you claim,
> >>> or there is not. Show me evidence of compression.
>
> >>**I cannot. Try the test and let me know what you hear. Perhaps you will
> >>have a different explanation. Negative tempco of gm is the only thing 
> >>that
> >>makes sense to me.
>
> > We are discussing one single parameter - compression. Once you start
> > with nonsense like seeing what you hear, you are no longer able to
> > isolate that parameter - you hear the sum of everything. And of course
> > mixed in with your "just listen" thing is all your bullshittery with
> > terms like "more dynamic". This is meaningless drivel, and the
> > standard recourse of the charlatan trying to claim superior skills of
> > discernment to the average man. It won't wash. You made the claim, now
> > substantiate it or withdraw it.
>
> **I'm uncertain of what you are demanding I withdraw. Are you demanding 
> that
> I withdraw my theory that pertains to why MOSFET amps sound so bad? Or are
> you demanding I withdraw what I and others hear?
>
> Given the problems that many people hear with MOSFET amps, I proferred a
> theory. I cannot validate that theory. If you have an alternate theory to
> explain what people hear, then please present it.
>
> As for claims of "superior skills of discernment", I make no such claims. 
> My
> hearing is just average. Anyone with average hearing will easily discern 
> the
> problems I speak of. I suggest you conduct your own test and confirm.
> Perhaps you will develop a more credible theory.
>
> --
> Trevor Wilsonwww.rageaudio.com.au- Hide quoted text -
>
> - Show quoted text -

More OSAF nonsense from Trevor. People do not hear 'problems' with
MOSFET (or any other properly functioning) amplifiers, they all sound
the same unless clipping. I still have on the cards an offer of £1,000
to anyone who can hear differences among amplifiers or cables under
level-matched DBT conditions. No one has even *tried* in the more than
ten years this offer has been on the table. I've tried it myself -
which is the point at which I stopped building amps and just bought
the cheapest that would drive my speakers properly. I still have my
trusty pure Class A Krell as a reference, but lots of others to which
I have *carefully* compared it sound exactly the same when driving
lighter speaker loads than my Apogees.

**Is that really you Lord Pinkerton?

Let's recap:

When you performed your comparisons, did you SPECIFICALLY, compare a 
primitive MOSFET, low bias Class A/B amp (Perreaux 2150) to a low bias Class 
A/B BJT amp (Phase Linear 400)?

Now, to address your kind offer. If we can find a way to make the deal such 
that I would cover my air fare and accommodation whilst in the UK, I will be 
only too happy to compare MY BJT amp to any low bias Class A/B MOSFET, high 
Global NFB amp you care to place in front of me. 1,000.00 Squid won't quite 
do it for me.


-- 
Trevor Wilson
www.rageaudio.com.au