Hi,

I've just put up a new webpage at

http://www.audiomisc.co.uk/cables/mains/StringTheory.html

This looks at the idea that 'special' mains cables might be useful because
they act as a form of 'RF Interference rejection filter'.

Was meaning to produce this a while ago, but got distracted, so the round
tuits only arrived recently!  :-)

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

Pardon me for asking this question, but if you want to filter mains borne 
interference, one would use a mains filter, so what would be the advantage 
of designing a cable to do the same thing?
Brian

-- 
Brian Gaff - briang1@blueyonder.co.uk
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Jim Lesurf"  wrote in message 
news:50b4f623a3noise@audiomisc.co.uk...
> Hi,
>
> I've just put up a new webpage at
>
> http://www.audiomisc.co.uk/cables/mains/StringTheory.html
>
> This looks at the idea that 'special' mains cables might be useful because
> they act as a form of 'RF Interference rejection filter'.
>
> Was meaning to produce this a while ago, but got distracted, so the round
> tuits only arrived recently!  :-)
>
> 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 <KIhIm.1696$Ym4.247@text.news.virginmedia.com>, Brian Gaff
 wrote:
> Pardon me for asking this question, but if you want to filter mains
> borne interference, one would use a mains filter, so what would be the
> advantage of designing a cable to do the same thing?

Good question. In fact one of the questions I had in mind that made me
decide to investigate this...  :-)

If you read my conclusions at the bottom of the webpage I think I make
clear that it seems to me that people would probably be better advised to
use a mains filter if they really need to filter RF on the mains.

But some vendors (such as Russ Andrews whose products and associated
claims prompted the examination) sell mains cables on the basis that they
can provide 'better' RFI filtering. Hence the page examines this idea. He
and Ben Duncan published the papers I referenced which present some
measured results and make various claims using them as a basis. So I
decided to have a look at this and see if taking the idea seriously would
lead <pun> anywhere.  :-)

Examine the references and you can then understand better why I examined
this as I did. One of the other reasons I did this was the things Ben wrote
about a 'Glissando Effect'. Readers might think that the 'special' mains
cables were doing something remarkable that isn't explainable by boring old
transmission line theory, etc.

I'm afraid that some vendors/makers of (often expensive) bits of
'audiophile gear' tend to say their products work on the basis of various
'Effects' which often seem to have eluded the notice of generations of
engineers and physical scientists. Given this I do tend to examine their
evidence to see if it stacks up. It often doesn't. Making mountains out of
molehills seems common.  

<ahem> I appreciate that may not surprise you.  :-)  However someone seems
to be buying what they sell, so it seems fair to at least investigate. Once
that is done, people can make their own minds up.


On 04 Nov in uk.rec.audio, Brian Gaff  wrote:

> The mains supply is not designed or indeed built with anything other
> than supply of AC at 50hz in mind. It is as likely to pick up rf before
> the socket as after it. 

Not sure "as likely" is correct as I have no evidence on that point. This
topic seems remarkably light on measured evidence, etc. But I agree that
the cables can also pick up RFI.

> The problem is really that we want a good supply inside the pieces of
> equipment. 

Agreed. Note my conclusions.

> Some use switch mode, some analogue systems, and one would
> hope for a reasonable system, a scope on the internal supply would be
> able to see any kind of rf coming in. You can make some pretty effective
> rf filters from ferrite cores and capacitors, since you just want to
> snub all out.

Agreed.

However some people make and sell mains cables on the basis that they
provide useful 'filtering'. So the point of the page I wrote was to see if
that idea stood up when taken seriously.

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

"Brian Gaff"  wrote in message 
news:KIhIm.1696$Ym4.247@text.news.virginmedia.com...
> Pardon me for asking this question, but if you want to filter mains borne 
> interference, one would use a mains filter, so what would be the advantage 
> of designing a cable to do the same thing?

**More profit margin for the dealer, distributor and manufacturer. Mains 
filters should, of course, be placed at the source of the interference, not 
on the equipment. Far and away, the best solution, is to use a dedicated 
mains connection for the hi fi system, if troubles persist. None of which 
helps the long suffering hi fi dealer and their quest for unimaginable 
wealth. You're better off paying your local electrician.


-- 
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson"  wrote in message 
news:7lel8gF3dl1fuU2@mid.individual.net...
>
> "Brian Gaff"  wrote in message 
> news:KIhIm.1696$Ym4.247@text.news.virginmedia.com...
>> Pardon me for asking this question, but if you want to filter mains borne 
>> interference, one would use a mains filter, so what would be the 
>> advantage of designing a cable to do the same thing?
>
> **More profit margin for the dealer, distributor and manufacturer. Mains 
> filters should, of course, be placed at the source of the interference, 
> not on the equipment.

I disagree. A filter, placed as close to the load as possible (preferably 
part of it), will reject interference from any source, including RF 
picked-up on the wiring.

> Far and away, the best solution, is to use a dedicated mains connection 
> for the hi fi system,

Dedecated from where? Perhaps if you have a dedicated connection all the way 
from the power station. But I can't see the advantage of merely having a 
dedicated connection from your own consumer unit.

> if troubles persist. None of which helps the long suffering hi fi dealer 
> and their quest for unimaginable wealth. You're better off paying your 
> local electrician.
>
You are better off using audio equipment that has been properly designed to 
be insensetive to interference.

David.

In article , David Looser
 wrote:
> "Trevor Wilson"  wrote in message
> news:7lel8gF3dl1fuU2@mid.individual.net...
> >
> > "Brian Gaff"  wrote in message
> > news:KIhIm.1696$Ym4.247@text.news.virginmedia.com...
> >> Pardon me for asking this question, but if you want to filter mains
> >> borne interference, one would use a mains filter, so what would be
> >> the advantage of designing a cable to do the same thing?
> >
> > **More profit margin for the dealer, distributor and manufacturer.
> > Mains filters should, of course, be placed at the source of the
> > interference, not on the equipment.

> I disagree. A filter, placed as close to the load as possible
> (preferably part of it), will reject interference from any source,
> including RF picked-up on the wiring.

That would get my vote as the best approach if you can't simply fix or
replace the source of RFI. But alas in some cases the source may be
inaccessible and unchangable by the person being annoyed by RFI.

> > Far and away, the best solution, is to use a dedicated mains
> > connection for the hi fi system,

> Dedecated from where? Perhaps if you have a dedicated connection all the
> way from the power station. But I can't see the advantage of merely
> having a dedicated connection from your own consumer unit.

Having the longest possible run that isn't common with a source might help.
But as with choosing cables it seems rather hit and miss to me.

> > if troubles persist. None of which helps the long suffering hi fi
> > dealer and their quest for unimaginable wealth. You're better off
> > paying your local electrician.
> >
> You are better off using audio equipment that has been properly designed
> to be insensetive to interference.

That also strikes me as preferred. If only because at some later date a new
source of RFI may crop up, and be outwith your control to fix at source.
Having to chase around neighbours trying to find if their fridge is the
source can be a PITA and lead to arguments.

So far as I could tell, making units like audio amps resist the common
levels of mains RFI in the UK was easy enough if you knew how to do it. But
I do agree that there will always be extreme cases where it can be much
harder if a specific source is very powerful and near.

Dealing with RFI for a tuner is harder as by definition it has to pick up a
given band so can't avoid being sensitive to any rubbish presented in that
band to its RF input. Should still be able to effectively deal with mains
RFI (or up the audio output leads) though.

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 message , David Looser 
 writes
>"Trevor Wilson"  wrote in message
>news:7lel8gF3dl1fuU2@mid.individual.net...
>>
>> "Brian Gaff"  wrote in message
>> news:KIhIm.1696$Ym4.247@text.news.virginmedia.com...
>>> Pardon me for asking this question, but if you want to filter mains borne
>>> interference, one would use a mains filter, so what would be the
>>> advantage of designing a cable to do the same thing?
>>
>> **More profit margin for the dealer, distributor and manufacturer. Mains
>> filters should, of course, be placed at the source of the interference,
>> not on the equipment.
>
>I disagree. A filter, placed as close to the load as possible (preferably
>part of it), will reject interference from any source, including RF
>picked-up on the wiring.
>
I think the real answer is "It depends".

Ideally, the source of the interference should be suppressed (by both 
screening and filtering), so that it emits no unreasonable level of 
interference (and ideally, of course, none at all). If everything was 
adequately suppressed, there would be no interference to be picked up by 
the mains feed to the susceptible equipment.

On the other hand, if interference is 'flying around', and you have no 
control over it, it would usually be better to insert any filter close 
to the susceptible equipment.

>> Far and away, the best solution, is to use a dedicated mains connection
>> for the hi fi system,
>
>Dedecated from where? Perhaps if you have a dedicated connection all the way
>from the power station. But I can't see the advantage of merely having a
>dedicated connection from your own consumer unit.
>
There could well be some advantage in not having something creating 
interference and something susceptible to interference sharing the same 
mains feed for most of the way from the consumer unit.

>> if troubles persist. None of which helps the long suffering hi fi dealer
>> and their quest for unimaginable wealth. You're better off paying your
>> local electrician.
>>
>You are better off using audio equipment that has been properly designed to
>be insensetive to interference.
>
Exactly! If you have audio equipment which gets interference via the 
mains power feed, then the quality of its design must be questioned.
-- 
Ian

Well all very interesting, but.

The mains supply is not designed or indeed built with anything other than 
supply of AC at 50hz in mind. It is as likely to pick up rf before the 
socket as after it. The problem is really that we want a good supply inside 
the pieces of equipment. Some use switch mode, some analogue systems, and 
one would hope for a reasonable system, a scope on the internal supply would 
be able to see any kind of rf coming in. You can make some pretty effective 
rf filters from ferrite cores and capacitors, since you just want to snub 
all out.

To me the biggest problems of  odd distortions occur because of.
several pieces of gear with different mains supply systems all sharing a 
common ground via cables that are prone to pick stuff up. Unless of course 
you are an optical freak that is..

Speaker cables that  can induce crap into the amp and finally,  high 
currents on transients inside the equipment modulating the supply enough to 
cause blurring of the sound.
Brian

-- 
Brian Gaff - briang1@blueyonder.co.uk
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Jim Lesurf"  wrote in message 
news:50b4f623a3noise@audiomisc.co.uk...
> Hi,
>
> I've just put up a new webpage at
>
> http://www.audiomisc.co.uk/cables/mains/StringTheory.html
>
> This looks at the idea that 'special' mains cables might be useful because
> they act as a form of 'RF Interference rejection filter'.
>
> Was meaning to produce this a while ago, but got distracted, so the round
> tuits only arrived recently!  :-)
>
> 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
>

"Ian Jackson"  wrote
>
> Ideally, the source of the interference should be suppressed (by both 
> screening and filtering), so that it emits no unreasonable level of 
> interference (and ideally, of course, none at all). If everything was 
> adequately suppressed, there would be no interference to be picked up by 
> the mains feed to the susceptible equipment.

Well indeed, in an ideal world that would be the case. But we don't live in 
an ideal world.
>
> On the other hand, if interference is 'flying around', and you have no 
> control over it, it would usually be better to insert any filter close to 
> the susceptible equipment.
>

As near as possible


>>> Far and away, the best solution, is to use a dedicated mains connection
>>> for the hi fi system,
>>
>>Dedecated from where? Perhaps if you have a dedicated connection all the 
>>way
>>from the power station. But I can't see the advantage of merely having a
>>dedicated connection from your own consumer unit.
>>
> There could well be some advantage in not having something creating 
> interference and something susceptible to interference sharing the same 
> mains feed for most of the way from the consumer unit.
>

That assumes that the interfering equipment is powered from the same circuit 
as the audio equipment. Not a likely scenario, and if it is the case there 
are simpler and cheaper ways of overcoming the problem than installing a 
dedicated power circuit.
The idea that such a dedicated mains connections is "far and away, the best 
solution" is just plain daft. Only an audiophool would think so.

David.

In message , David Looser 
 writes
>"Ian Jackson"  wrote
>>

>> On the other hand, if interference is 'flying around', and you have no
>> control over it, it would usually be better to insert any filter close to
>> the susceptible equipment.
>>
>
>As near as possible
>
Usually true, but I could tell you a tale where this wasn't the case.
-- 
Ian

"Ian Jackson"  wrote in message 
news:7kcVIPWcC18KFwnX@g3ohx.demon.co.uk...
> In message , David Looser 
>  writes
>>"Ian Jackson"  wrote
>>>
>
>>> On the other hand, if interference is 'flying around', and you have no
>>> control over it, it would usually be better to insert any filter close 
>>> to
>>> the susceptible equipment.
>>>
>>
>>As near as possible
>>
> Usually true, but I could tell you a tale where this wasn't the case.
> -- 

Could you? So why mention it if you aren't going to?

David.

In message , David Looser 
 writes
>"Ian Jackson"  wrote in message
>news:7kcVIPWcC18KFwnX@g3ohx.demon.co.uk...
>> In message , David Looser
>>  writes
>>>"Ian Jackson"  wrote
>>>>
>>
>>>> On the other hand, if interference is 'flying around', and you have no
>>>> control over it, it would usually be better to insert any filter close
>>>> to
>>>> the susceptible equipment.
>>>>
>>>
>>>As near as possible
>>>
>> Usually true, but I could tell you a tale where this wasn't the case.
>> --
>
>Could you? So why mention it if you aren't going to?
>
Well, it's a bit long and involved, and somewhat OT for this NG 
(involving radio transmissions and TV). But if you really want me 
to........
-- 
Ian

"Ian Jackson"  wrote in message
news:oJkBD5B+s98KFwmO@g3ohx.demon.co.uk...
> In message , David Looser
>  writes
>>"Ian Jackson"  wrote in message
>>news:7kcVIPWcC18KFwnX@g3ohx.demon.co.uk...
>>> In message , David Looser
>>>  writes
>>>>"Ian Jackson"  wrote
>>>>>
>>>
>>>>> On the other hand, if interference is 'flying around', and you have no
>>>>> control over it, it would usually be better to insert any filter close
>>>>> to
>>>>> the susceptible equipment.
>>>>>
>>>>
>>>>As near as possible
>>>>
>>> Usually true, but I could tell you a tale where this wasn't the case.
>>> --
>>
>>Could you? So why mention it if you aren't going to?
>>
> Well, it's a bit long and involved, and somewhat OT for this NG (involving
> radio transmissions and TV).

Then how is it relevant to the subject under discussion?

> But if you really want me to........

That's up to you. But if you don't we cannot judge whether your story has 
any relevance to this thread, nor in what way it "wasn't the case".

David.

In message , David Looser 
 writes
>"Ian Jackson"  wrote in message
>news:oJkBD5B+s98KFwmO@g3ohx.demon.co.uk...
>> In message , David Looser
>>  writes
>>>"Ian Jackson"  wrote in message
>>>news:7kcVIPWcC18KFwnX@g3ohx.demon.co.uk...
>>>> In message , David Looser
>>>>  writes
>>>>>"Ian Jackson"  wrote
>>>>>>
>>>>
>>>>>> On the other hand, if interference is 'flying around', and you have no
>>>>>> control over it, it would usually be better to insert any filter close
>>>>>> to
>>>>>> the susceptible equipment.
>>>>>>
>>>>>
>>>>>As near as possible
>>>>>
>>>> Usually true, but I could tell you a tale where this wasn't the case.
>>>> --
>>>
>>>Could you? So why mention it if you aren't going to?
>>>
>> Well, it's a bit long and involved, and somewhat OT for this NG (involving
>> radio transmissions and TV).
>
>Then how is it relevant to the subject under discussion?
>
>> But if you really want me to........
>
>That's up to you. But if you don't we cannot judge whether your story has
>any relevance to this thread, nor in what way it "wasn't the case".
>
OK. I'll try to be brief.

Interference usually occurs because the current of the interfering 
signal flows from the (inter)connecting leads and into (and through) the 
affected equipment. However, there are occasions where the equipment is 
affected by the VOLTAGE on the leads, especially if the equipment is 
badly screened, and has some sensitive, high impedance circuitry.

If the filter works by presenting a high impedance to the (typically 
common-mode) interfering signal, the interference gets blocked, and 'has 
nowhere to go'. As a result, the voltage on the unfiltered side of the 
filter can be very much higher than when the filter isn't present. This 
high voltage can 'jump over the filter', and into the affected 
equipment. It could be that the interference is actually worse than when 
there is no filter present.

In this sort of situation, it is necessary to re-think things. The 
filter could be changed to one which diverts the interference, rather 
than block it. Alternatively, it is worth trying placing the filter at a 
short distance from the affected equipment (maybe a foot or two), so 
that the interference has much further to 'jump'  - and, of course, also 
ensure that the 'hot' side of the lead is dressed away from the 
equipment.

So, I'm not saying that a filter should NOT be located as close to the 
affected equipment as possibly. What I'm saying is that there are 
occasions when this just might not be the best place.
-- 
Ian

"Ian Jackson"  wrote

<snip>
>
> In this sort of situation, it is necessary to re-think things. The filter 
> could be changed to one which diverts the interference, rather than block 
> it. Alternatively, it is worth trying placing the filter at a short 
> distance from the affected equipment (maybe a foot or two), so that the 
> interference has much further to 'jump'  - and, of course, also ensure 
> that the 'hot' side of the lead is dressed away from the equipment.
>
> So, I'm not saying that a filter should NOT be located as close to the 
> affected equipment as possibly. What I'm saying is that there are 
> occasions when this just might not be the best place.
> -- 

You are making so many assumptions here, about what we meant by a "filter", 
how it works and the mechanisms by which the interference reaches the 
affected equipment!

An interference filter should (and usually does) provide a shunt path for 
the interfering signal *as well* as a high-impedance towards the affected 
equipment.

What you seem to be talking about when you talk about the interference 
"jumping" is direct RF pick-up within the affected equipment (or by signal 
leads connected to it). Yes this does happen and it's an issue that needs to 
be addressed by the designer. I remain to be convinced that placing an 
in-line filter, designed to attenuate mains-borne interference, at a 
distance from the equipment helps in this regard at all.

At the end of the day the designer needs to consider *all* possibilities for 
interference entering the equipment and deal with each in the most 
appropriate way.

David.

In message , David Looser 
 writes
>"Ian Jackson"  wrote
>
><snip>
>>
>> In this sort of situation, it is necessary to re-think things. The filter
>> could be changed to one which diverts the interference, rather than block
>> it. Alternatively, it is worth trying placing the filter at a short
>> distance from the affected equipment (maybe a foot or two), so that the
>> interference has much further to 'jump'  - and, of course, also ensure
>> that the 'hot' side of the lead is dressed away from the equipment.
>>
>> So, I'm not saying that a filter should NOT be located as close to the
>> affected equipment as possibly. What I'm saying is that there are
>> occasions when this just might not be the best place.
>> --
>
>You are making so many assumptions here, about what we meant by a "filter",
>how it works and the mechanisms by which the interference reaches the
>affected equipment!
>
I'm making no 'assumptions' at all. I said "If the filter works by 
presenting a high impedance to the (typically common-mode) interfering 
signal, the interference gets blocked, and 'has nowhere to go' ". Note 
the 'If'.

>An interference filter should (and usually does) provide a shunt path for
>the interfering signal *as well* as a high-impedance towards the affected
>equipment.
>
It depends on the filter. Some mains filters filter only the live and 
neutral, and shunt interference to the earth lead - which conveniently 
bypasses the whole filter! This does little to suppress longitudinal 
currents.

>What you seem to be talking about when you talk about the interference
>"jumping" is direct RF pick-up within the affected equipment (or by signal
>leads connected to it). Yes this does happen and it's an issue that needs to
>be addressed by the designer.

Absolutely correct. On one particular occasion, I actually got RF burns 
from a TV plug as soon as I unplugged it from the TV!

> I remain to be convinced that placing an
>in-line filter, designed to attenuate mains-borne interference, at a
>distance from the equipment helps in this regard at all.
>
If the interference is external pickup, the 'distance' must not be 
sufficient to allow interference to be picked up again on the 
'unfiltered' part of the lead. If it's already 'in' the mains cable, it 
probably doesn't matter too much where the filter is.

>At the end of the day the designer needs to consider *all* possibilities for
>interference entering the equipment and deal with each in the most
>appropriate way.
>
Quite! All I'm doing is casting a very little aspersion on your "As near 
as possible" statement. It ain't necessarily so (but it usually is).
-- 
Ian

David Looser wrote:
>
> At the end of the day the designer needs to consider *all*
> possibilities for interference entering the equipment and deal with
> each in the most appropriate way.
>

Including via the speaker leads. I once had an amp that functioned as a 
great Radio Moscow receiver until I fitted some RF filtering in the speaker 
leads.

In message , TonyL 
 writes
>David Looser wrote:
>>
>> At the end of the day the designer needs to consider *all*
>> possibilities for interference entering the equipment and deal with
>> each in the most appropriate way.
>>
>
>Including via the speaker leads. I once had an amp that functioned as a
>great Radio Moscow receiver until I fitted some RF filtering in the speaker
>leads.
>
I'm using a very old Amstrad IC 2000 Mk3 [1] as the amplifier for my 
computer audio. It too picks up SW radio at night time - clearly audible 
when the computer is switched off. Presumably Sir Alan (now Lord Sugar) 
must have overlooked something. Shame on him! I thought he always 
strived for perfection. Must investigate (one of these days).
[1] A car boot sale purchase 20 years ago, and lost in the loft until 
recently.
-- 
Ian

In article , Ian Jackson
 wrote:
> In message , David Looser
>  writes
> >"Ian Jackson"  wrote
>

> >An interference filter should (and usually does) provide a shunt path
> >for the interfering signal *as well* as a high-impedance towards the
> >affected equipment.
> >
> It depends on the filter. Some mains filters filter only the live and
> neutral, and shunt interference to the earth lead - which conveniently
> bypasses the whole filter! This does little to suppress longitudinal
> currents.

Your descriptions are a bit ambiguous so it isn't entirely clear what you
mean. However I presume you are referring to common-mode RF variations
where in essence the Live, Neutral, and Earth wires are all changing in
potential in the same way wrt to zero electrostatic potential?

If so, then yes, a filter that just shunts to the earth wire won't help you
much if you want to stop such a common mode from continuing along the
cable. But you would then need to wonder if it would have any effect on the
operation of something like an audio system *if* that is correctly
designed.

FWIW I personally tend to be a fan of having filtering near to the input
where the mains enters the case of the unit, and for that case to be a
shield. This generally seems to work well in my experience.

Alas, as the equipment designer you usually have no control at all over
what people then connect at the other ends of all the leads!

> >What you seem to be talking about when you talk about the interference
> >"jumping" is direct RF pick-up within the affected equipment (or by
> >signal leads connected to it). Yes this does happen and it's an issue
> >that needs to be addressed by the designer.

> Absolutely correct. On one particular occasion, I actually got RF burns
> from a TV plug as soon as I unplugged it from the TV!

How did you establish it was an RF burn and not due to mains power leakage
to that point? I've certainly had tingles, etc, from TV sockets due to the
crappy way their PSUs are made and their poor standards of dealing with
grounding, etc. But that was due to either mains or EHF floating the
chassis well away from true Earth (electrostatic) potential. What in a TV
set would generate so much RF power as to cause a burn?

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 , TonyL
 wrote:
> David Looser wrote:
> >
> > At the end of the day the designer needs to consider *all*
> > possibilities for interference entering the equipment and deal with
> > each in the most appropriate way.
> >

> Including via the speaker leads. I once had an amp that functioned as a
> great Radio Moscow receiver until I fitted some RF filtering in the
> speaker leads.

That is one of the reasons I personally always prefer to have an output
network including a blocking inductor. It also helps protect the amp from
wild variations in loading at RF from one situation to another. And can
reduce the peak currents required for some waveforms.

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

"Ian Jackson"  wrote in message 
news:gQmTltRwhA9KFwep@g3ohx.demon.co.uk...
> In message , David Looser 
>  writes
>>
>>You are making so many assumptions here, about what we meant by a 
>>"filter",
>>how it works and the mechanisms by which the interference reaches the
>>affected equipment!
>>
> I'm making no 'assumptions' at all. I said "If the filter works by 
> presenting a high impedance to the (typically common-mode) interfering 
> signal, the interference gets blocked, and 'has nowhere to go' ". Note the 
> 'If'.

Yes, I noticed the "if". Your assumptions came earlier when you were making 
assumptions about what a filter might be and what it does. The assumptions 
that lead to your assertion that interference "jumps".

David.

"Ian Jackson"  wrote
>
> Absolutely correct. On one particular occasion, I actually got RF burns 
> from a TV plug as soon as I unplugged it from the TV!
>
I simply don't believe that! *RF* burns, from a TV? impossible!

You might have got a burn from the EHT system, or shocks from the HT system, 
or indeed from stored charge on mains filter capacitors. But you'd need a 
medium to high-powered transmitter to get *RF* burns.

David.

In message , David Looser 
 writes
>"Ian Jackson"  wrote
>>
>> Absolutely correct. On one particular occasion, I actually got RF burns
>> from a TV plug as soon as I unplugged it from the TV!
>>
>I simply don't believe that! *RF* burns, from a TV? impossible!
>
I said I got RF burns from the TV PLUG (ie the male plug on the end of 
the aerial downlead).

>You might have got a burn from the EHT system, or shocks from the HT system,
>or indeed from stored charge on mains filter capacitors.

>But you'd need a
>medium to high-powered transmitter to get *RF* burns.
>
Is 400W on 80m next door enough? I must admit that I was surprised when 
I suddenly felt a strange feeling in my fingers when I unplugged the 
serial lead (which had a 'proper' metal B&L plug on it).

This TV set appeared to be particularly susceptible to interference from 
voltage pickup. A braid-breaking highpass filter immediately at the TV 
socket actually made things worse. The cure was to have the filter 
around 2 foot away, at floor level, with the rest of the coax routed 
well away from the TV set. In fact, after the interference had been 
cleared, you could again see signs of it if you laid your hand on the 
top of the set.

Of course, an alternative (but, in this situation, less convenient) 
approach might have been to add an earth connection to coax braid - 
connected either to the mains earth or (preferably) to an external 
earth. This would have both diverted RF currents past the TV set, and 
also killed the RF voltage on the coax.

As I indicated previously, I'm not suggesting that interference filters 
should not normally be positioned close to the affected equipment. What 
I am trying to get over is that there are occasions when this might not 
be the best place to put them. But any advice such as 'always as close 
as possible' is definitely not always correct.
-- 
Ian

"Ian Jackson"  wrote
>>

> Is 400W on 80m next door enough?

From which I gather that your next-door neighbour is a radio amateur. Is he 
in the habit of exceeding the allowed power by such a handsome margin?

Is that enough? Depends on the degree of coupling. If your TV aerial is very 
close to his transmitting aerial possibly.

> I must admit that I was surprised when I suddenly felt a strange feeling 
> in my fingers when I unplugged the serial lead (which had a 'proper' metal 
> B&L plug on it).

What else were you touching at the time? And does a "strange feeling" amount 
to a burn?
>
> This TV set appeared to be particularly susceptible to interference from 
> voltage pickup. A braid-breaking highpass filter immediately at the TV 
> socket actually made things worse. The cure was to have the filter around 
> 2 foot away, at floor level, with the rest of the coax routed well away 
> from the TV set. In fact, after the interference had been cleared, you 
> could again see signs of it if you laid your hand on the top of the set.
>
> Of course, an alternative (but, in this situation, less convenient) 
> approach might have been to add an earth connection to coax braid - 
> connected either to the mains earth or (preferably) to an external earth. 
> This would have both diverted RF currents past the TV set, and also killed 
> the RF voltage on the coax.

And is a legal requirement in many countries. Though whether it would have 
cured your interference problem would depend on the impedance of the earth 
path at the frequency of the interfering signal. Quite likely it wouldn't, 
though it would certainly help in conjunction with a braid-breaker and 
high-pass filter.
>
> As I indicated previously, I'm not suggesting that interference filters 
> should not normally be positioned close to the affected equipment. What I 
> am trying to get over is that there are occasions when this might not be 
> the best place to put them. But any advice such as 'always as close as 
> possible' is definitely not always correct.
> -- 

With respect your story has little to do with the subject under discussion. 
We were talking about mains-borne interference to audio equipment, not very 
strong RF interference applied to the aerial sockets of radio receivers. 
The path that RF takes depends on a variety of factors, many of them less 
than obvious. Under conditions such as you mention re-radiation of the 
interfering signal from the co-ax braid directly into the input stage of the 
receiver is likely. Pick up of mains-borne interference re-radiated by mains 
wiring and picked up by audio circuitry isn't.

David.

Ian Jackson wrote:
>>
> I'm using a very old Amstrad IC 2000 Mk3 [1] as the amplifier for my
> computer audio. It too picks up SW radio at night time - clearly
> audible when the computer is switched off. Presumably Sir Alan (now
> Lord Sugar) must have overlooked something. Shame on him! I thought
> he always strived for perfection. Must investigate (one of these
> days). [1] A car boot sale purchase 20 years ago, and lost in the
> loft until recently.
>

My Radio Moscow receiver was actually a Texan amp ! Bought as a kit some 30 
years ago and still working when I retired it to the loft 3 years ago. 
Anybody remember them ?

In message , David Looser 
 writes
>"Ian Jackson"  wrote
>>>
>
>> Is 400W on 80m next door enough?
>
>From which I gather that your next-door neighbour is a radio amateur. Is he
>in the habit of exceeding the allowed power by such a handsome margin?

By how much do you think he is "exceeding the allowed power by such a 
handsome margin"?
>
>Is that enough? Depends on the degree of coupling. If your TV aerial is very
>close to his transmitting aerial possibly.
>
A UHF TV aerial actually picks up very little of the interfering signal. 
Almost all of the pick-up will be on the coax downlead.

>> I must admit that I was surprised when I suddenly felt a strange feeling
>> in my fingers when I unplugged the serial lead (which had a 'proper' metal
>> B&L plug on it).
>
>What else were you touching at the time? And does a "strange feeling" amount
>to a burn?

I was touching nothing - other than that I was holding the aerial lead 
and plug
>>
>> This TV set appeared to be particularly susceptible to interference from
>> voltage pickup. A braid-breaking highpass filter immediately at the TV
>> socket actually made things worse. The cure was to have the filter around
>> 2 foot away, at floor level, with the rest of the coax routed well away
>> from the TV set. In fact, after the interference had been cleared, you
>> could again see signs of it if you laid your hand on the top of the set.
>>
>> Of course, an alternative (but, in this situation, less convenient)
>> approach might have been to add an earth connection to coax braid -
>> connected either to the mains earth or (preferably) to an external earth.
>> This would have both diverted RF currents past the TV set, and also killed
>> the RF voltage on the coax.
>
>And is a legal requirement in many countries.

In the UK, it is not a legal requirement to provide an earth for a 
domestic TV aerial and downlead.

>Though whether it would have
>cured your interference problem would depend on the impedance of the earth
>path at the frequency of the interfering signal. Quite likely it wouldn't,
>though it would certainly help in conjunction with a braid-breaker and
>high-pass filter.

On the contrary, I suspect that it would have.

>>
>> As I indicated previously, I'm not suggesting that interference filters
>> should not normally be positioned close to the affected equipment. What I
>> am trying to get over is that there are occasions when this might not be
>> the best place to put them. But any advice such as 'always as close as
>> possible' is definitely not always correct.
>> --
>
>With respect your story has little to do with the subject under discussion.

Well, I told you it was rather OT, but you dragged it out of me!

>We were talking about mains-borne interference to audio equipment, not very
>strong RF interference applied to the aerial sockets of radio receivers.

Yes. I appreciate the difference. However, if we're talking interference 
conducted via the mains wiring, it probably makes little difference 
whether the filter is installed close to the equipment causing the 
interference, or whether it is close to the equipment being interfered 
with.

>The path that RF takes depends on a variety of factors, many of them less
>than obvious. Under conditions such as you mention re-radiation of the
>interfering signal from the co-ax braid directly into the input stage of the
>receiver is likely.

The 'input stage' is actually unlikely to be the route by which the 
interference enters the TV set. It is more likely to be the video (and 
audio) circuits.

>Pick up of mains-borne interference re-radiated by mains
>wiring and picked up by audio circuitry isn't.
>
Obviously, the nature of interference injected into the mains (whether 
differentially or longitudinally) will be different from that picked up 
by very strong SW RF signals (which is almost invariably picked up 
longitudinally on the braid of a coax downlead. But, as I said, always 
fitting a filter as close as possible to the affected equipment may not 
always be necessary and, on the odd occasion, may not be the way to do 
it.
-- 
Ian

In message , TonyL 
 writes
>Ian Jackson wrote:
>>>
>> I'm using a very old Amstrad IC 2000 Mk3 [1] as the amplifier for my
>> computer audio. It too picks up SW radio at night time - clearly
>> audible when the computer is switched off. Presumably Sir Alan (now
>> Lord Sugar) must have overlooked something. Shame on him! I thought
>> he always strived for perfection. Must investigate (one of these
>> days). [1] A car boot sale purchase 20 years ago, and lost in the
>> loft until recently.
>>
>
>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit some 30
>years ago and still working when I retired it to the loft 3 years ago.
>Anybody remember them ?
>
Ah! The Wireless World design from circa 1965/6!
I've got one in the loft. I only bought the PCB, and got the rest of the 
bits separately. I got it partly assembled it, but never finished it off 
(and undoubtedly never will). A works colleague DID complete his but, 
when he switched it on, he blew the cones out of his rather expensive 
loudspeakers. Apparently, the original early design tended to oscillate 
rather violently at around 3MHz.
-- 
Ian

"Ian Jackson"  wrote in message 
news:pQ5RVSBMnE9KFwfL@g3ohx.demon.co.uk...
> In message , David Looser 
>  writes
>>"Ian Jackson"  wrote
>>>>
>>
>>> Is 400W on 80m next door enough?
>>
>>From which I gather that your next-door neighbour is a radio amateur. Is 
>>he
>>in the habit of exceeding the allowed power by such a handsome margin?
>
> By how much do you think he is "exceeding the allowed power by such a 
> handsome margin"?

Depending on the conversion efficiency of his PA stage, around 4-5dB.
>>
> A UHF TV aerial actually picks up very little of the interfering signal. 
> Almost all of the pick-up will be on the coax downlead.

Well yes, obviously. But presumably your downlead runs all the way from the 
aerial?
>
>
> I was touching nothing - other than that I was holding the aerial lead and 
> plug
>>>

You practice levitation do you?
>>
>>And is a legal requirement in many countries.
>
> In the UK, it is not a legal requirement to provide an earth for a 
> domestic TV aerial and downlead.
>
That's why I phrased it as I did.
>
> On the contrary, I suspect that it would have.

Then we disagree. The impedance of earth connections can be significant.
>
>>>>
> Yes. I appreciate the difference. However, if we're talking interference 
> conducted via the mains wiring, it probably makes little difference 
> whether the filter is installed close to the equipment causing the 
> interference, or whether it is close to the equipment being interfered 
> with.

Although a mains lead is unlikely to act as a transmitting aerial, it can 
make quite a good receiving one. So as close to the audio equipment as 
possible reduces the length of receiving "aerial" to a minimum.
> >
> The 'input stage' is actually unlikely to be the route by which the 
> interference enters the TV set. It is more likely to be the video (and 
> audio) circuits.
>
You think so?

> But, as I said, always fitting a filter as close as possible to the 
> affected equipment may not always be necessary and, on the odd occasion, 
> may not be the way to do it.

In the case of mains-borne interference I would still say "always", your 
story has no bearing on that.

David.

"TonyL"  wrote in message 
news:QfedneJFJ9jT1WnXnZ2dnUVZ8lWdnZ2d@bt.com...
> Ian Jackson wrote:
>>>
>> I'm using a very old Amstrad IC 2000 Mk3 [1] as the amplifier for my
>> computer audio. It too picks up SW radio at night time - clearly
>> audible when the computer is switched off. Presumably Sir Alan (now
>> Lord Sugar) must have overlooked something. Shame on him! I thought
>> he always strived for perfection. Must investigate (one of these
>> days). [1] A car boot sale purchase 20 years ago, and lost in the
>> loft until recently.
>>
>
> My Radio Moscow receiver was actually a Texan amp ! Bought as a kit some 
> 30 years ago and still working when I retired it to the loft 3 years ago. 
> Anybody remember them ?

Yes. I made one up (from a kit) for a local voluntary group to use as a 
small PA system/music system many moons ago. It worked quite well into a 
pair of Celestion Ditton 15s.

David.

>
>

In message , David Looser 
 writes
>"Ian Jackson"  wrote in message
>news:pQ5RVSBMnE9KFwfL@g3ohx.demon.co.uk...
>> In message , David Looser
>>  writes
>>>"Ian Jackson"  wrote
>>>>>
>>>
>>>> Is 400W on 80m next door enough?
>>>
>>>From which I gather that your next-door neighbour is a radio amateur. Is
>>>he
>>>in the habit of exceeding the allowed power by such a handsome margin?
>>
>> By how much do you think he is "exceeding the allowed power by such a
>> handsome margin"?
>
>Depending on the conversion efficiency of his PA stage, around 4-5dB.
>>>
Is there something you know about the UK (Full) Amateur Radio licence 
conditions which I don't know about? Please do tell.

>> A UHF TV aerial actually picks up very little of the interfering signal.
>> Almost all of the pick-up will be on the coax downlead.
>
>Well yes, obviously. But presumably your downlead runs all the way from the
>aerial?

On a good day, yes!
>>
>>
>> I was touching nothing - other than that I was holding the aerial lead and
>> plug
>>>>
>
>You practice levitation do you?

I'm not really sure what you mean. I would have probably standing on a 
carpet, pretty well insulated, with the soles of my feet in contact with 
my socks, which were, in turn, touching the insides of my shoes, which 
were touching the aforesaid carpet. However, I would have had sufficient 
capacity to earth to experience the sensation of RF burning (but not, 
fortunately, the exquisite aroma of burning flesh).

>>>
>>>And is a legal requirement in many countries.
>>
>> In the UK, it is not a legal requirement to provide an earth for a
>> domestic TV aerial and downlead.
>>
>That's why I phrased it as I did.
>>
>> On the contrary, I suspect that it would have.
>
>Then we disagree. The impedance of earth connections can be significant.

Undoubtedly. It is possible that the impedance of any earth bypass 
connection would not have been low enough, but I certainly would not 
have expected it not to work well enough.

>>
>>>>>
>> Yes. I appreciate the difference. However, if we're talking interference
>> conducted via the mains wiring, it probably makes little difference
>> whether the filter is installed close to the equipment causing the
>> interference, or whether it is close to the equipment being interfered
>> with.
>
>Although a mains lead is unlikely to act as a transmitting aerial, it can
>make quite a good receiving one. So as close to the audio equipment as
>possible reduces the length of receiving "aerial" to a minimum.

But this applies to interference picked up on the mains wiring - not 
interference conducted from A to B. If it IS interference pick-up, I 
don't really disagree with you. However, like the TV aerial downlead, it 
does depend on the nature and frequency of the interference, and the 
mechanism of how the interference enters the affected equipment.

>> >
>> The 'input stage' is actually unlikely to be the route by which the
>> interference enters the TV set. It is more likely to be the video (and
>> audio) circuits.
>>
>You think so?
>
I certainly do. TV tuners (and to a much lesser extent, the IF circuits) 
have always been relatively well-screened. On the other hand, the video 
and audio circuits usually had little or no screening and poor (high) RF 
local ground impedances, so they were therefore much more susceptible to 
especially the lower frequency part of the RF spectrum.

>> But, as I said, always fitting a filter as close as possible to the
>> affected equipment may not always be necessary and, on the odd occasion,
>> may not be the way to do it.
>
>In the case of mains-borne interference I would still say "always", your
>story has no bearing on that.
>
In the majority of cases, I wouldn't disagree - but I can't agree with 
'always'!
-- 
Ian

"Ian Jackson"

>>
>>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit some 
>>30
>>years ago and still working when I retired it to the loft 3 years ago.
>>Anybody remember them ?
>>
> Ah! The Wireless World design from circa 1965/6!


** Nonsense.

The "Texan"  20 + 20 watt integrated amp was published in Practical Wireless 
in May 1972.

Credited to an R. Mann, it was apparently cobbled together by staff members 
at Texas Instruments.




....  Phil

In message , Phil Allison 
 writes
>
>"Ian Jackson"
>
>>>
>>>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit some
>>>30
>>>years ago and still working when I retired it to the loft 3 years ago.
>>>Anybody remember them ?
>>>
>> Ah! The Wireless World design from circa 1965/6!
>
>
>** Nonsense.
>
>The "Texan"  20 + 20 watt integrated amp was published in Practical Wireless
>in May 1972.
>
>Credited to an R. Mann, it was apparently cobbled together by staff members
>at Texas Instruments.
>
I'm sure you're right. However, I'm pretty certain that I half-built 
mine in 1965 or 66 - and certainly no later than 68. It would have had 
to been then, because I moved to another floor, and no longer regularly 
saw the guy who wrecked his speakers.

Mine used (I think) OC24s or 28s. Could it be that the 1972 Texan was a 
'sorted out' version of the mid-60s model. Or was mine something 
completely different?
-- 
Ian

"Ian Jackson"
 Phil Allison
>>
>>>>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit some 
>>>>30 years ago and still working when I retired it to the loft 3 years 
>>>>ago.
>>>>Anybody remember them ?
>>>>
>>> Ah! The Wireless World design from circa 1965/6!
>>
>>
>>** Nonsense.
>>
>>The "Texan"  20 + 20 watt integrated amp was published in Practical 
>>Wireless
>>in May 1972.
>>
>>Credited to an R. Mann, it was apparently cobbled together by staff 
>>members
>>at Texas Instruments.
>>
> I'm sure you're right. However, I'm pretty certain that I half-built mine 
> in 1965 or 66 - and certainly no later than 68. It would have had to been 
> then, because I moved to another floor, and no longer regularly saw the 
> guy who wrecked his speakers.
>
> Mine used (I think) OC24s or 28s. Could it be that the 1972 Texan was a 
> 'sorted out' version of the mid-60s model. Or was mine something 
> completely different?


** You are totally confused.

The OC24 and OC28 were Germanium TO3 types made by Philips et alia.




.....   Phil

In message , Phil Allison 
 writes
>
>"Ian Jackson"
> Phil Allison
>>>
>>>>>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit some
>>>>>30 years ago and still working when I retired it to the loft 3 years
>>>>>ago.
>>>>>Anybody remember them ?
>>>>>
>>>> Ah! The Wireless World design from circa 1965/6!
>>>
>>>
>>>** Nonsense.
>>>
>>>The "Texan"  20 + 20 watt integrated amp was published in Practical
>>>Wireless
>>>in May 1972.
>>>
>>>Credited to an R. Mann, it was apparently cobbled together by staff
>>>members
>>>at Texas Instruments.
>>>
>> I'm sure you're right. However, I'm pretty certain that I half-built mine
>> in 1965 or 66 - and certainly no later than 68. It would have had to been
>> then, because I moved to another floor, and no longer regularly saw the
>> guy who wrecked his speakers.
>>
>> Mine used (I think) OC24s or 28s. Could it be that the 1972 Texan was a
>> 'sorted out' version of the mid-60s model. Or was mine something
>> completely different?
>
>
>** You are totally confused.
>
>The OC24 and OC28 were Germanium TO3 types made by Philips et alia.
>
I may be confused - but not 'totally'. Indeed, the OCs were 
Philips/Mullard (not Texas). So if it wasn't a Texan (which it probably 
wasn't), just what was the amplifier which I half-built in the mid 60s?
-- 
Ian

"Ian Jackson"
> Phil Allison
>>>>
>>>>>>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit 
>>>>>>some
>>>>>>30 years ago and still working when I retired it to the loft 3 years
>>>>>>ago.
>>>>>>Anybody remember them ?
>>>>>>
>>>>> Ah! The Wireless World design from circa 1965/6!
>>>>
>>>>
>>>>** Nonsense.
>>>>
>>>>The "Texan"  20 + 20 watt integrated amp was published in Practical
>>>>Wireless in May 1972.
>>>>
>>>>Credited to an R. Mann, it was apparently cobbled together by staff
>>>>members at Texas Instruments.
>>>>
>>> I'm sure you're right. However, I'm pretty certain that I half-built 
>>> mine
>>> in 1965 or 66 - and certainly no later than 68. It would have had to 
>>> been
>>> then, because I moved to another floor, and no longer regularly saw the
>>> guy who wrecked his speakers.
>>>
>>> Mine used (I think) OC24s or 28s. Could it be that the 1972 Texan was a
>>> 'sorted out' version of the mid-60s model. Or was mine something
>>> completely different?
>>
>>
>>** You are totally confused.
>>
>>The OC24 and OC28 were Germanium TO3 types made by Philips et alia.
>>
> I may be confused - but not 'totally'.


**  Fraid you are  -  pal.


> Indeed, the OCs were Philips/Mullard (not Texas). So if it wasn't a Texan 
> (which it probably wasn't), just what was the amplifier which I half-built 
> in the mid 60s?


**  Huh ???

Not anyone's problem but yours to know that one.

Try going up to  YOUR  loft and  FIND  the pile of junk and take a look at 
it.

Shithead.



.....  Phil

In message , Phil Allison 
 writes
>"Ian Jackson"
>> Phil Allison
>>>>>
>>>>>>>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit
>>>>>>>some
>>>>>>>30 years ago and still working when I retired it to the loft 3 years
>>>>>>>ago.
>>>>>>>Anybody remember them ?
>>>>>>>
>>>>>> Ah! The Wireless World design from circa 1965/6!
>>>>>
>>>>>
>>>>>** Nonsense.
>>>>>
>>>>>The "Texan"  20 + 20 watt integrated amp was published in Practical
>>>>>Wireless in May 1972.
>>>>>
>>>>>Credited to an R. Mann, it was apparently cobbled together by staff
>>>>>members at Texas Instruments.
>>>>>
>>>> I'm sure you're right. However, I'm pretty certain that I half-built
>>>> mine
>>>> in 1965 or 66 - and certainly no later than 68. It would have had to
>>>> been
>>>> then, because I moved to another floor, and no longer regularly saw the
>>>> guy who wrecked his speakers.
>>>>
>>>> Mine used (I think) OC24s or 28s. Could it be that the 1972 Texan was a
>>>> 'sorted out' version of the mid-60s model. Or was mine something
>>>> completely different?
>>>
>>>
>>>** You are totally confused.
>>>
>>>The OC24 and OC28 were Germanium TO3 types made by Philips et alia.
>>>
>> I may be confused - but not 'totally'.
>
>
>**  Fraid you are  -  pal.
>
>
>> Indeed, the OCs were Philips/Mullard (not Texas). So if it wasn't a Texan
>> (which it probably wasn't), just what was the amplifier which I half-built
>> in the mid 60s?
>
>
>**  Huh ???
>
>Not anyone's problem but yours to know that one.
>
>Try going up to  YOUR  loft and  FIND  the pile of junk and take a look at
>it.
>
>Shithead.
>
I'm sure you're absolutely right about this. I've been waiting for 
around 40 years to get the problem sorted out, and it needed you to come 
alone and help me. I'm sure I'll continue to be eternally grateful for 
your kind, generous and helpful advice.
-- 
Ian

"Ian Jackoff"

>>
>>>>>>>>My Radio Moscow receiver was actually a Texan amp ! Bought as a kit
>>>>>>>>some
>>>>>>>>30 years ago and still working when I retired it to the loft 3 years
>>>>>>>>ago.
>>>>>>>>Anybody remember them ?
>>>>>>>>
>>>>>>> Ah! The Wireless World design from circa 1965/6!
>>>>>>
>>>>>>
>>>>>>** Nonsense.
>>>>>>
>>>>>>The "Texan"  20 + 20 watt integrated amp was published in Practical
>>>>>>Wireless in May 1972.
>>>>>>
>>>>>>Credited to an R. Mann, it was apparently cobbled together by staff
>>>>>>members at Texas Instruments.
>>>>>>
>>>>> I'm sure you're right. However, I'm pretty certain that I half-built
>>>>> mine
>>>>> in 1965 or 66 - and certainly no later than 68. It would have had to
>>>>> been
>>>>> then, because I moved to another floor, and no longer regularly saw 
>>>>> the
>>>>> guy who wrecked his speakers.
>>>>>
>>>>> Mine used (I think) OC24s or 28s. Could it be that the 1972 Texan was 
>>>>> a
>>>>> 'sorted out' version of the mid-60s model. Or was mine something
>>>>> completely different?
>>>>
>>>>
>>>>** You are totally confused.
>>>>
>>>>The OC24 and OC28 were Germanium TO3 types made by Philips et alia.
>>>>
>>> I may be confused - but not 'totally'.
>>
>>
>>**  Fraid you are  -  pal.
>>
>>
>>> Indeed, the OCs were Philips/Mullard (not Texas). So if it wasn't a 
>>> Texan
>>> (which it probably wasn't), just what was the amplifier which I 
>>> half-built
>>> in the mid 60s?
>>
>>
>>**  Huh ???
>>
>>Not anyone's problem but yours to know that one.
>>
>>Try going up to  YOUR  loft and  FIND  the pile of junk and take a look at
>>it.
>>
>>Shithead.
>>
> I'm sure you're absolutely right about this. I've been waiting for around 
> 40 years to get the problem sorted out, and it needed you to come alone 
> and help me. I'm sure I'll continue to be eternally grateful for your 
> kind, generous and helpful advice.
> -- 
> Ian


** Living in Australia all my life  -   I believe I was almost 18 years old 
when I first discovered that " pommy "  and " cunt " were two separate words 
...........



.....  Phil

Ian Jackson wrote:
>>
> I'm sure you're absolutely right about this. I've been waiting for
> around 40 years to get the problem sorted out, and it needed you to
> come alone and help me. I'm sure I'll continue to be eternally
> grateful for your kind, generous and helpful advice.
>

He he. A brush with the resident nutter.

I've got the Texan docs in front of me right now. I see that Henry's Radio 
were distributing them for £28.50 although I visited the people assembling 
the kits...somewhere in Leicester...and got one for a discounted price.

Here's some info:

The design was featured in Practical Wireless May to August 1972. Output 
devices were TIP41 and TIP42 driven by BC181 and BC182 respectively in a 
modified Darlington configuration. Unlike a standard Darlington it had some 
20dB of gain to compensate for the limited output voltage swing from the 
preceding op-amp stage. (Limited by slew rate, BTW)

The 3 op-amps in each channel were SN72748P types.

A few choice bits from the spec:
Sensitivity was 2.5 mV for full 20 Watts output into 8 Ohms.

S/N -60dB (mag pickup)

At 20 W into 8 Ohms distortion was given as 0.09% at 1kHz

-3 dB frequency response was 5Hz to 35kHz
-1 dB was 7Hz to 22kHz

O/P impedance < 10E-3 Ohms

Not bad for something "cobbled together".

Interesting comment on the first page:
"Don't forget to add VAT after 1st April 1973"

Hope this helps.

In message , TonyL 
 writes
>Ian Jackson wrote:
>>>
>> I'm sure you're absolutely right about this. I've been waiting for
>> around 40 years to get the problem sorted out, and it needed you to
>> come alone and help me. I'm sure I'll continue to be eternally
>> grateful for your kind, generous and helpful advice.
>>
>
>He he. A brush with the resident nutter.
>
Yes. I've seen some of his rantings.

>I've got the Texan docs in front of me right now. I see that Henry's Radio
>were distributing them for £28.50 although I visited the people assembling
>the kits...somewhere in Leicester...and got one for a discounted price.
>
>Here's some info:
>
>The design was featured in Practical Wireless May to August 1972. Output
>devices were TIP41 and TIP42 driven by BC181 and BC182 respectively in a
>modified Darlington configuration. Unlike a standard Darlington it had some
>20dB of gain to compensate for the limited output voltage swing from the
>preceding op-amp stage. (Limited by slew rate, BTW)
>
>The 3 op-amps in each channel were SN72748P types.
>
>A few choice bits from the spec:
>Sensitivity was 2.5 mV for full 20 Watts output into 8 Ohms.
>
>S/N -60dB (mag pickup)
>
>At 20 W into 8 Ohms distortion was given as 0.09% at 1kHz
>
>-3 dB frequency response was 5Hz to 35kHz
>-1 dB was 7Hz to 22kHz
>
>O/P impedance < 10E-3 Ohms
>
>Not bad for something "cobbled together".
>
>Interesting comment on the first page:
>"Don't forget to add VAT after 1st April 1973"
>
>Hope this helps.

Thanks. After sleeping on it, I reckon that I was mistaken in thinking 
that the Texan came out in the mid-to-late 60s. I suddenly remembered 
the complementary pair - TIP41 and 42 and thought "Oh dear. The OC24s 
were something else!" (I know I used them when I converted a 12-to-250V 
vibrator pack to 'solid state'). But I definitely do have a half-built 
Texan in the loft.

The time I was mis-remembering was probably when electronic ignition 
circuit were all the rage. Several of us at work built these things 
(both Wireless World and Practical Wireless designs), with very limited 
success. At best, the car still ran almost as well as it did with the 
make-break points (but that's another story).
-- 
Ian

"TonyLunatic"

 He he. A brush with the resident nutter.

**  Yeah  -   YOU   sunny boy.


> I've got the Texan docs in front of me right now.

** Shame the retarded troll does not even know what one is  -

    FUCKWIT !!!


> The design was featured in Practical Wireless May to August 1972.


**  Stale news  -  sonny boy.


> The 3 op-amps in each channel were SN72748P types.


**  So  crappy LM748s by another number.


> S/N -60dB (mag pickup)


** An  APPALLINGLY noisy  POS.

    Fuck off.



 ....   Phil

"Ian Jackson"


**  Fuck  off  to hell   !!!!

 You  TROLLING   POMMYCUNT  !!!




....  Phil

"Ian Jackoff is a TROLL"

>
>>You practice levitation do you?


** The lying autistic fuckwit practices Astral Travelling whenever he likes.

  Right now,  he on his way to the outer rings of Saturn.



> I'm not really sure what you mean.

** The fuckwit is not sure what  ANYTHING  means.


> I would have probably standing on a carpet, pretty well insulated, with 
> the soles of my feet in contact with my socks, which were, in turn, 
> touching the insides of my shoes, which were touching the aforesaid 
> carpet. However, I would have had sufficient capacity to earth to 
> experience the sensation of RF burning (but not, fortunately, the 
> exquisite aroma of burning flesh).


** The lying pile of anencephalic dog's dung is just making it up as he goes 
along.

     Wot a fucking hoot.



.....  Phil