How can I stop the 15625 kHz line deflection frequency from infecting my 
entire Hi-Fi system whenever any video equipment including my TV, video 
sender, video recorder or digital STB is switched on, other than switching 
the whole lot off or disconnecting it from my amp or anything connoted to it 
connected to my amp. Even when the video input is not selected there is 
still a residual -60dB deflection tone present on all the audio outputs of 
my AV amp, whereas if I switch the video equipment off the audio is clean.

Would having a Hi-Fi system with isolated Balanced Line Inputs and Outputs 
prevent my audio being interfered with and why don't AV amplifier 
manufactures start making them?

Agamemnon wrote:
> How can I stop the 15625 kHz line deflection frequency from infecting my 
> entire Hi-Fi system whenever any video equipment including my TV, video 
> sender, video recorder or digital STB is switched on, other than 
> switching the whole lot off or disconnecting it from my amp or anything 
> connoted to it connected to my amp. Even when the video input is not 
> selected there is still a residual -60dB deflection tone present on all 
> the audio outputs of my AV amp, whereas if I switch the video equipment 
> off the audio is clean.
> 
> Would having a Hi-Fi system with isolated Balanced Line Inputs and 
> Outputs prevent my audio being interfered with and why don't AV 
> amplifier manufactures start making them?

Use the Optical out from your digital STB.

"Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
news:tM2dneKFuYFnhfrVnZ2dneKdnZydnZ2d@eclipse.net.uk...
> How can I stop the 15625 kHz line deflection frequency from infecting my 
> entire Hi-Fi system whenever any video equipment including my TV, video 
> sender, video recorder or digital STB is switched on, other than switching 
> the whole lot off or disconnecting it from my amp or anything connoted to 
> it connected to my amp. Even when the video input is not selected there is 
> still a residual -60dB deflection tone present on all the audio outputs of 
> my AV amp, whereas if I switch the video equipment off the audio is clean.
>
> Would having a Hi-Fi system with isolated Balanced Line Inputs and Outputs 
> prevent my audio being interfered with and why don't AV amplifier 
> manufactures start making them?

can you hear it?

Geoff Pearson wrote:

> can you hear it? 

If he can now, he won't by the time he hits middle age.

-- 
Mark
Please replace invalid and invalid with gmx and net to reply.

Geoff Pearson wrote:
> "Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
> news:tM2dneKFuYFnhfrVnZ2dneKdnZydnZ2d@eclipse.net.uk...
>> How can I stop the 15625 kHz line deflection frequency from infecting my 
>> entire Hi-Fi system whenever any video equipment including my TV, video 
>> sender, video recorder or digital STB is switched on, other than switching 
>> the whole lot off or disconnecting it from my amp or anything connoted to 
>> it connected to my amp. Even when the video input is not selected there is 
>> still a residual -60dB deflection tone present on all the audio outputs of 
>> my AV amp, whereas if I switch the video equipment off the audio is clean.
>>
>> Would having a Hi-Fi system with isolated Balanced Line Inputs and Outputs 
>> prevent my audio being interfered with and why don't AV amplifier 
>> manufactures start making them?
> 
> can you hear it? 
> 
> 
He should be able too...

You need to find out where its getting. I'd guess it might be the earth side 
of any connectors, but if you are saying even if the two systems are not 
physically connected, then its the speaker cables you need to suspect. Maybe 
some ferrite rings on them.

I had an amp which picked  tv whistle up and far worse than this, it got 
radar pulses, and the local sea cadets as well... Maybe you have a plasma 
tv.

Brian

-- 
Brian Gaff....Note, this account does not accept Bcc: email.
 graphics are great, but the blind can't hear them
Email: briang1@blueyonder.co.uk
______________________________________________________________________________________________________________


"Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
news:tM2dneKFuYFnhfrVnZ2dneKdnZydnZ2d@eclipse.net.uk...
> How can I stop the 15625 kHz line deflection frequency from infecting my 
> entire Hi-Fi system whenever any video equipment including my TV, video 
> sender, video recorder or digital STB is switched on, other than switching 
> the whole lot off or disconnecting it from my amp or anything connoted to 
> it connected to my amp. Even when the video input is not selected there is 
> still a residual -60dB deflection tone present on all the audio outputs of 
> my AV amp, whereas if I switch the video equipment off the audio is clean.
>
> Would having a Hi-Fi system with isolated Balanced Line Inputs and Outputs 
> prevent my audio being interfered with and why don't AV amplifier 
> manufactures start making them?

"Mark Carver" <mark.carver@invalid.invalid> wrote in message 
news:6cp1npF3fsg82U1@mid.individual.net...
> Geoff Pearson wrote:
>
>> can you hear it?
>
> If he can now, he won't by the time he hits middle age.

Yes, I used to be annoyed by a similar annoying whine from the wife, but for 
the last ten years I don't seem to have heard it. I'm only aware of it when 
she throws something and says "I don't think you're even LISTENING!"

Bill

"Brian Gaff"  wrote in message 
news:BmJ9k.17666$E41.4309@text.news.virginmedia.com...
> You need to find out where its getting. I'd guess it might be the earth 
> side of any connectors, but if you are saying even if the two systems are 
> not physically connected, then its the speaker cables you need to suspect. 
> Maybe some ferrite rings on them.

Would ferrites stop an unwanted AF signal without stopping the wanted ones? 
How would you fit it? With both conductors running through and around it, or 
what?

>
> I had an amp which picked  tv whistle up and far worse than this, it got 
> radar pulses, and the local sea cadets as well

Sounds like a rather gay amp to me, using 'radar' and picking up sea cadets 
. . .

Bill

Agamemnon wrote:
> How can I stop the 15625 kHz line deflection frequency from infecting my 
> entire Hi-Fi system whenever any video equipment including my TV, video 
> sender, video recorder or digital STB is switched on,

Faulty TV. CE "Conducted Emmsions" Mains filtering kaput ...

-- 
Adrian C

"Glenn Millar"  wrote in message 
news:SMidnc3FgYxwoPrVnZ2dnUVZ8sPinZ2d@posted.plusnet...
> Agamemnon wrote:
>> How can I stop the 15625 kHz line deflection frequency from infecting my 
>> entire Hi-Fi system whenever any video equipment including my TV, video 
>> sender, video recorder or digital STB is switched on, other than 
>> switching the whole lot off or disconnecting it from my amp or anything 
>> connoted to it connected to my amp. Even when the video input is not 
>> selected there is still a residual -60dB deflection tone present on all 
>> the audio outputs of my AV amp, whereas if I switch the video equipment 
>> off the audio is clean.
>>
>> Would having a Hi-Fi system with isolated Balanced Line Inputs and 
>> Outputs prevent my audio being interfered with and why don't AV amplifier 
>> manufactures start making them?
>
> Use the Optical out from your digital STB.

Yes, I've done that, but since my video recorder and other stuff also needs 
to be connected to the amp and that is also connected to the TV the 15625 
kHz line deflection tone is still infecting my system on every audio input.

"Geoff Pearson"  wrote in message 
news:6cp1eeF3grf54U1@mid.individual.net...
>
> "Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
> news:tM2dneKFuYFnhfrVnZ2dneKdnZydnZ2d@eclipse.net.uk...
>> How can I stop the 15625 kHz line deflection frequency from infecting my 
>> entire Hi-Fi system whenever any video equipment including my TV, video 
>> sender, video recorder or digital STB is switched on, other than 
>> switching the whole lot off or disconnecting it from my amp or anything 
>> connoted to it connected to my amp. Even when the video input is not 
>> selected there is still a residual -60dB deflection tone present on all 
>> the audio outputs of my AV amp, whereas if I switch the video equipment 
>> off the audio is clean.
>>
>> Would having a Hi-Fi system with isolated Balanced Line Inputs and 
>> Outputs prevent my audio being interfered with and why don't AV amplifier 
>> manufactures start making them?
>
> can you hear it?

I can hear it on the TV. If it goes above -40 or -50dB or I turn the volume 
up I can hear it on any analogue recording I make.

"Adrian C" <email@here.invalid> wrote in message 
news:6cpn46F3gla0tU1@mid.individual.net...
> Agamemnon wrote:
>> How can I stop the 15625 kHz line deflection frequency from infecting my 
>> entire Hi-Fi system whenever any video equipment including my TV, video 
>> sender, video recorder or digital STB is switched on,
>
> Faulty TV. CE "Conducted Emmsions" Mains filtering kaput ...

And the STB is faulty too and the video sender?

It's nothing to do with the mains. All electrical cable has resistance so 
anything fed through it will leave a tiny potential difference across the 
earth/ground screen of the cable. If your Hi-Fi system is at a different 
earth potential from the cable from the TV, which it will be because the TV 
cable is carrying 15625 kHz AC and the Hi-Fi isn't then any recording 
equipment connected to it which is at 0V is also is going to pick up the AC 
through the ground connections even if the TV is not selected since the TV 
cable is being loaded by the amp and since the ground wiring is inductive, 
15625 kHz is going to cause a greater PD than any other frequency, and 
that's before we even get to stray capacitance, so it will appear at the 
input of the recorder. The only way I can see of stopping this is for all AV 
amps and video equipment to use isolated balanced line connections, not RCA 
connections. And then there the possibility of the speaker cabling being 
responsible for the same reason so that needs to be isolated too. Now the 
thing is I am only getting 15625 kHz at -60 dB, not any other kind of audio 
cross talk at any other frequency, so the line deflection voltage must be 
really high, really really, high, since normal audio line out peeks at 2V 
RMS.

>
> -- 
> Adrian C

Agamemnon wrote:
> 
>> Faulty TV. CE "Conducted Emmsions" Mains filtering kaput ...
> 
> And the STB is faulty too and the video sender?
> 

Nope, just your TV. It is trashing the mains with interference. Learn to 
isolate sources.

Put the lot in a charity shop / skip / freecycle and buy something else. 
Or run into the open arms of Russ Andrews...

Your hifi and 15,625KHz obsession, your choice :-)

--
Adrian C


-- 
Adrian C

"Adrian C" <email@here.invalid> wrote in message 
news:6cpuusF3il1abU1@mid.individual.net...
> Agamemnon wrote:
>>
>>> Faulty TV. CE "Conducted Emmsions" Mains filtering kaput ...
>>
>> And the STB is faulty too and the video sender?
>>
>
> Nope, just your TV. It is trashing the mains with interference. Learn to 
> isolate sources.

You're talking absolute rubbish. I already said that I still get 15625 kHz 
through my amp with only the STB switched on or only the video sender on and 
everything else off. Learn to read and understand English properly.

>
> Put the lot in a charity shop / skip / freecycle and buy something else. 
> Or run into the open arms of Russ Andrews...
>
> Your hifi and 15,625KHz obsession, your choice :-)
>

You Idiot!

> --
> Adrian C
>
>
> -- 
> Adrian C

Agamemnon wrote:
> You're talking absolute rubbish. I already said that I still get 15625 
> kHz through my amp with only the STB switched on or only the video 
> sender on and everything else off. Learn to read and understand English 
> properly.

You actually didn't write it that clear initially. I think a lot of 
people have problems trying to understand your patter and where you are 
comming from, it's all drowned in your pseudo science confused arguments 
and -60dB measurements (with what!?)

Your HiFi has immunity problems. So the following still stands.
> 
>>
>> Put the lot in a charity shop / skip / freecycle and buy something 
>> else. Or run into the open arms of Russ Andrews...
>>

>> Your hifi and 15,625KHz obsession, your choice :-)
>>
> 
> You Idiot!
> 

Yeah, but baiting you is so much fun....

Toodle pip ;-)

-- 
Adrian C

"Adrian C" <email@here.invalid> wrote in message 
news:6cq36iF3i274uU1@mid.individual.net...
> Agamemnon wrote:
>> You're talking absolute rubbish. I already said that I still get 15625 
>> kHz through my amp with only the STB switched on or only the video sender 
>> on and everything else off. Learn to read and understand English 
>> properly.
>
> You actually didn't write it that clear initially. I think a lot of

It was perfectly clear for anyone that actually read what was written 
instead of what they thought up.

> people have problems trying to understand your patter and where you are 
> comming from, it's all drowned in your pseudo science confused arguments 
> and -60dB measurements (with what!?)

With Audacity -60dBFSD. See my earlier posts.

>
> Your HiFi has immunity problems. So the following still stands.

Nope. The 15625 kHz is still there even when the Hi-Fi is switched off. It's 
some sort of grounding pickup problem.

"Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
news:Tsadnci4natJRvrVnZ2dnUVZ8uqdnZ2d@eclipse.net.uk...
> Nope. The 15625 kHz is still there even when the Hi-Fi is switched off. 
> It's some sort of grounding pickup problem.

Sorry, am I missing something ?

How do you manage to "hear" 15625 kHz ? That's way out with the human 
audible
range.

Besides which, no TV generates that sort of frequency, except perhaps
through some instability in the RF stage.

In message , Torvic 
 wrote
>
>"Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
>news:Tsadnci4natJRvrVnZ2dnUVZ8uqdnZ2d@eclipse.net.uk...
>> Nope. The 15625 kHz is still there even when the Hi-Fi is switched 
>>off.  It's some sort of grounding pickup problem.
>
>Sorry, am I missing something ?
>
>How do you manage to "hear" 15625 kHz ? That's way out with the human 
>audible
>range.
>
>Besides which, no TV generates that sort of frequency, except perhaps
>through some instability in the RF stage.
>

I assumed he meant 15625Hz = 64us = line period.

-- 
Alan
news2006 {at} amac {dot} f2s {dot} com

On Sun, 29 Jun 2008 06:09:17 +0100, Agamemnon <agamemnon@hello.to.NO_SPAM>
wrote:

> How can I stop the 15625 kHz

Clueless.

> Would having a Hi-Fi system with isolated Balanced Line Inputs and Outputs 
> prevent my audio being interfered with and why don't AV amplifier 
> manufactures start making them? 

Possibly or possibly not. 'cos it costs more and nobody would buy it.

In article ,
   Torvic  wrote:

> "Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
> news:Tsadnci4natJRvrVnZ2dnUVZ8uqdnZ2d@eclipse.net.uk...
> > Nope. The 15625 kHz is still there even when the Hi-Fi is switched off. 
> > It's some sort of grounding pickup problem.

> Sorry, am I missing something ?

> How do you manage to "hear" 15625 kHz ? That's way out with the human
> audible range.

No, it's not.  High frequency response does drop off with age, but 20kHz is
well within the range of young people.


> Besides which, no TV generates that sort of frequency, except perhaps
> through some instability in the RF stage.

'Old fashioned' tv sets with CRTs create that frequency in their line scan
stages.

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

On Wed, 02 Jul 2008 07:47:13 +0100, charles 
wrote:

>> How do you manage to "hear" 15625 kHz ? That's way out with the human
>> audible range.
> 
> No, it's not.  High frequency response does drop off with age, but 20kHz is
> well within the range of young people.

Read what it says, not what you THINK it says. It's obvious, innit?
The clueless Agamoron can't see it though as it repeatedly makes the same
mistake.

In article <slrng6lkrk.or8.abuse@news.pr.network>, Paul Ratcliffe wrote:
> > Would having a Hi-Fi system with isolated Balanced Line Inputs and Outputs 
> > prevent my audio being interfered with and why don't AV amplifier 
> > manufactures start making them? 
> 
> Possibly or possibly not. 'cos it costs more and nobody would buy it.

And in most domestic hi-fi systems not involving cable runs of hundreds of 
metres it would make absolutely no difference.

No hi-fi enthusiast would be daft enough to spend more money on something that 
made no difference, would they?

Rod.

In article <slrng6mfbl.qct.abuse@news.pr.network>,
   Paul Ratcliffe <abuse@orac12.clara34.co56.uk78> wrote:
> On Wed, 02 Jul 2008 07:47:13 +0100, charles 
> wrote:

> >> How do you manage to "hear" 15625 kHz ? That's way out with the human
> >> audible range.
> > 
> > No, it's not.  High frequency response does drop off with age, but
> > 20kHz is well within the range of young people.

> Read what it says, not what you THINK it says. It's obvious, innit?
> The clueless Agamoron can't see it though as it repeatedly makes the same
> mistake.

Indeed - sorry.

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

"Paul Ratcliffe" <abuse@orac12.clara34.co56.uk78> wrote in message 
news:slrng6mfbl.qct.abuse@news.pr.network...
> On Wed, 02 Jul 2008 07:47:13 +0100, charles 
> 
> wrote:
>
>>> How do you manage to "hear" 15625 kHz ? That's way out with the human
>>> audible range.
>>
>> No, it's not.  High frequency response does drop off with age, but 20kHz 
>> is
>> well within the range of young people.
>
> Read what it says, not what you THINK it says. It's obvious, innit?
> The clueless Agamoron can't see it though as it repeatedly makes the same
> mistake.

Why don't you just point out that the decimal point is missing you deranged 
impotent PRICK and try to be helpful for once in your life! 15.625 kHz. Are 
you happy now arsehole?

"Agamemnon" <agamemnon@hello.to.NO_SPAM> wrote in message 
news:uZGdnaQ7abLKK_bVnZ2dnUVZ8trinZ2d@eclipse.net.uk...
> Why don't you just point out that the decimal point is missing you 
> deranged impotent PRICK and try to be helpful for once in your life! 
> 15.625 kHz. Are you happy now arsehole?
>
Impotence, pricks, arseholes . . . mein Gott, zis patient is getting vorse 
and vorse!

Bill

"Roderick Stewart"  wrote in 
message news:VA.00000437.01113bad@escapetime.removethisbit.myzen.co.uk...
> In article <slrng6lkrk.or8.abuse@news.pr.network>, Paul Ratcliffe wrote:
>> > Would having a Hi-Fi system with isolated Balanced Line Inputs and 
>> > Outputs
>> > prevent my audio being interfered with and why don't AV amplifier
>> > manufactures start making them?
>>
>> Possibly or possibly not. 'cos it costs more and nobody would buy it.
>
> And in most domestic hi-fi systems not involving cable runs of hundreds of
> metres it would make absolutely no difference.
>
> No hi-fi enthusiast would be daft enough to spend more money on something 
> that
> made no difference, would they?

What is the point of buying an HD audio AV amp system capable of playing 
back 24bit 96kHz audio and having the sound infected with a clearly audible 
15.625 kHz tone which is totally impossible to get rid off if you have any 
video equipment switched on in the same room?

Even if I disconnect the TV from my AV amp and that means not only 
unplugging the cables from the TV audio out, but also unplugging the DVD 
player from the switch box even when it is switched to something else and 
disconnecting my STB too, it's still being infected by 15.625 kHz because 
the TV is connected to the mains earth, as is the AV amp and everything 
else. If I switch the TV off, the interference goes down by 6 dB but there 
is still between -60dB and -70dB coming from the STB through the earth 
cabling. If I disconnect the amp from my computer than the audio feed to my 
computer is clean. But as soon as I connect even one wire between the ground 
on the amp and the ground on the computer audio lead, which is terminated by 
a 1.2k resistor across the centre core and ground to emulate the output 
impedance of the amp the interference is back.

-60dB is 2mV RMS since the line out from most audio devices is 2V RMS. The 
video output level from a DVD player, STB or TV SCART is normally 1 V p-p 
which is 0.35 V RMS and that is terminated by 75 ohms, thus the current 
flowing through the cables is about 5mA.

Now 5mA flowing through a cable with a resistance of 0.4 ohms will create a 
2mV potential difference across it. And 0.4 ohms is around about the 
resistance I have measured for the outer screen of my AV leads, and audio 
lead cabling as well as the earth cabling from one socket to the other 
(which also has surge protectors along it), bearing in mind that this 
measurement is at the extreme low end of the scale on my meter so it could 
be an ohm or more greater or less, but it's definitely not zero. All cable 
has resistance. 0.1 ohms would account for a -70dB drop on the audio.  Most 
of the resistance is probably caused by bad or dirty contacts, and most AV 
and audio leads use really thin outer sheathing, but the point is the 
resistance is enough to account for the -60dB 15.625 kHz tone that is 
infecting any audio I try to record, and I can't get rid of it. Since it's 
at audio frequency RF filter capacitors make no difference.

In article , Agamemnon wrote:
> What is the point of buying an HD audio AV amp system capable of playing 
> back 24bit 96kHz audio and having the sound infected with a clearly audible 
> 15.625 kHz tone which is totally impossible to get rid off if you have any 
> video equipment switched on in the same room?
> 
> Even if I disconnect the TV from my AV amp and that means not only 
> unplugging the cables from the TV audio out, but also unplugging the DVD 
> player from the switch box even when it is switched to something else and 
> disconnecting my STB too, it's still being infected by 15.625 kHz because 
> the TV is connected to the mains earth, as is the AV amp and everything 
> else. If I switch the TV off, the interference goes down by 6 dB but there 
> is still between -60dB and -70dB coming from the STB through the earth 
> cabling. If I disconnect the amp from my computer than the audio feed to my 
> computer is clean. But as soon as I connect even one wire between the ground 
> on the amp and the ground on the computer audio lead, which is terminated by 
> a 1.2k resistor across the centre core and ground to emulate the output 
> impedance of the amp the interference is back.

Interesting. Let me guess - your computer and the audio equipment are plugged 
into different mains sockets in different parts of the room? You've got audio 
cables going both to and from the computer? Perhaps you also take the TV audio 
for the amplifier from sockets on the back of the TV itself, so effectively 
you've got audio signals going to and from that as well? Does any of this 
describe your setup? 

For what it's worth, all my hi-fi and TV equipment is in one shelf unit and 
powered from the same mains socket, the TV set being fed from one of the mains 
splitters in this unit and not from a separate wall socket. TV audio for the 
hi-fi amplifier is taken directly from phono sockets on the SCART switch box 
and not from the back of the TV, so the TV is effectively only being used as a 
picture display with only power and RGB video being fed to it. The computer is 
not connected to any of this. Thus there are no wiring loops where a signal 
would go both to and from any piece of equipment (e.g. computer or TV set), and 
no mains cable loops as everything is powered from what amounts to a star 
point, i.e. the set of 13A splitters in base of the AV shelf unit.

If you need to connect signals to and from some remote piece of equipment such 
as a computer, there may be a case for using balanced feeds and isolated earths 
just for those cable runs, but the heart of the system should work in a star 
formation with a common earth, particularly if it's all close together as it 
generally is in a domestic setup. This is only general advice because I don't 
know the details of your setup, but maybe it will help.

Rod.

"Roderick Stewart"  wrote in 
message news:VA.00000438.03515e56@escapetime.removethisbit.myzen.co.uk...
> In article , Agamemnon 
> wrote:
>> What is the point of buying an HD audio AV amp system capable of playing
>> back 24bit 96kHz audio and having the sound infected with a clearly 
>> audible
>> 15.625 kHz tone which is totally impossible to get rid off if you have 
>> any
>> video equipment switched on in the same room?
>>
>> Even if I disconnect the TV from my AV amp and that means not only
>> unplugging the cables from the TV audio out, but also unplugging the DVD
>> player from the switch box even when it is switched to something else and
>> disconnecting my STB too, it's still being infected by 15.625 kHz because
>> the TV is connected to the mains earth, as is the AV amp and everything
>> else. If I switch the TV off, the interference goes down by 6 dB but 
>> there
>> is still between -60dB and -70dB coming from the STB through the earth
>> cabling. If I disconnect the amp from my computer than the audio feed to 
>> my
>> computer is clean. But as soon as I connect even one wire between the 
>> ground
>> on the amp and the ground on the computer audio lead, which is terminated 
>> by
>> a 1.2k resistor across the centre core and ground to emulate the output
>> impedance of the amp the interference is back.
>
> Interesting. Let me guess - your computer and the audio equipment are 
> plugged
> into different mains sockets in different parts of the room? You've got 
> audio

Nope. The computer is plugged into a UPS socket and the TV, VCR, STB is 
plugged into an extension cable running from the same UPS. The AV amp is 
plugged into a surge protector going into the mains socket on the other side 
of the room.

> cables going both to and from the computer? Perhaps you also take the TV 
> audio
> for the amplifier from sockets on the back of the TV itself,

Yes, VCR to TV to amp, so I can play VHS videos through my amp with 
surround.

>so effectively
> you've got audio signals going to and from that as well?

Did have until I disconnected the lot and isolated the AV amp from any 
contact with the TV, other than though the mains earthing. It still picked 
up the 15.625 kHz at about -60dB give or take 10dB.

>Does any of this
> describe your setup?

See above.

>
> For what it's worth, all my hi-fi and TV equipment is in one shelf unit 
> and
> powered from the same mains socket, the TV set being fed from one of the 
> mains
> splitters in this unit and not from a separate wall socket. TV audio for 
> the
> hi-fi amplifier is taken directly from phono sockets on the SCART switch 
> box
> and not from the back of the TV, so the TV is effectively only being used 
> as a
> picture display with only power and RGB video being fed to it. The 
> computer is
> not connected to any of this. Thus there are no wiring loops where a 
> signal
> would go both to and from any piece of equipment (e.g. computer or TV 
> set), and
> no mains cable loops as everything is powered from what amounts to a star
> point, i.e. the set of 13A splitters in base of the AV shelf unit.
>
> If you need to connect signals to and from some remote piece of equipment 
> such
> as a computer, there may be a case for using balanced feeds and isolated 
> earths
> just for those cable runs, but the heart of the system should work in a 
> star
> formation with a common earth, particularly if it's all close together as 
> it
> generally is in a domestic setup. This is only general advice because I 
> don't
> know the details of your setup, but maybe it will help.

I've just tried connecting the AV amp to the same extension cable as the TV, 
VCR etc, which comes from the UPS that the computer is plugged into and the 
15.625 kHz tone is now at -50dB when recoding from the AV amp with a free 
line in selected or the FM Tuner selected from the AV amp (with the TV, STB 
connected to it etc. but switched out). In other words there is no 
difference in levels from plugging the amp into a separate surge protector 
plugged directly into the mains from a different wall socket.

If I place a couple of 1.2k or 22k resistors across the L and R inputs to 
the computer at the end of an RCA-3.5mm cable, the audio is completely free 
of the 15.625 kHz, unless I place the RCA-3.5mm cable near the TV (about 1m 
from it) and then it starts picking up the 15.625 kHz at about -70dB 
to -80dB. For some reason or other the 22k resistor accross the computer 
input produces less hiss and picks up less mains hum (at 100 Hz plus 
harmonics, mostly inaudible unless I bring the gain up) than the 1.2k 
resister.

When I recorded a test sample from "My Family" from my STB after the Tennis, 
when the actors were speaking the 15.625 kHz level was at -60dB, but when 
the audience laughter track was mixed in, the 15.625 kHz level was 10dB 
higher at -50dB (plus there is an additional tone at 15.8 kHz at -62 to -71 
dB throughout which I think could be a computer monitor being used in the 
studio running at 833x625 resolution and synced at 24.886 Hz unless its VLF 
submarine transmissions from Rugby). Now if the audience laughter track is 
producing a resultant -50dB, 15.625 kHz tone this means the BBC's audience 
mics are also being infected by the line deflection at levels of -54dB 
(where 0dB is 2V RMS). Don't the BBC use balanced mics?

>
> Rod.
>

In article ,
   Agamemnon <agamemnon@hello.to.NO_SPAM> wrote:

[Snip]

> Don't the BBC use balanced mics?

yes they do, but my memory from many years ago is that -50dB for any
interfering signals on tv sound was felt to be adequate.  And sound desks
used to be filtered at 15kHz to stop line frequency interference getting
out.

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

In article ,
Agamemnon <agamemnon@hello.to.NO_SPAM> wrote:

>What is the point of buying an HD audio AV amp system capable of playing 
>back 24bit 96kHz audio

Buggered if I know.

-- Richard
-- 
Please remember to mention me / in tapes you leave behind.