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Q:Channel Separation problem.

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Anonymous
January 1, 2005 8:42:30 PM

Archived from groups: rec.audio.tech (More info?)

Is it normal for some sound to leak to the other channel when the
volume pushed to the max with one channel input RCA unplugged?

After eliminating one by one, now the problem points to the PreAmp. I
have tried with all other inputs ( CD, video, Aux etc) and the result
is the same. The appears to be some leaking to the other channel at
high volume and High frequencies above 10khz. (too lazy to measure -
but high pitch female voice can be heard).

I believe the spec said something like 110db but now maybe the figure
could be half of that.

Any help much appreciated.

Thanks
Anonymous
January 2, 2005 4:36:32 AM

Archived from groups: rec.audio.tech (More info?)

Thanks but unable to understand "load 10k".

What I have done was to disconnect , say my left input, and push my
balance all the way to left with music being fed into the right
channel.Strangely, I do hear my left speaker. If I reverse the cables
than the right speaker can be heard. I tried with my two other mini
compos and get the same result. But I must push my volume control to
the max or atl east to the vey very loud level to hear the faint sound
from the speaker.

Is this known as "cross talk"? Am I correct to say that most pre amp
leaks some signal to the other channel. I have never actually done this
before and therefore can't tell for sure if it was present from day
one.

If I leave the balance in the centre but with one input unplugged than
I don't hear any music from the other channel, so it appears that under
normal listening level the audible "crosstalk" is negligeble.

I think this problem is too common. Anybody out there done the same?
Just be careful to reset the volume.
Anonymous
January 2, 2005 6:09:54 AM

Archived from groups: rec.audio.tech (More info?)

In <1104630150.595856.238660@c13g2000cwb.googlegroups.com>, on 01/01/05

at 05:42 PM, tchelvam@hotmail.com said:


>Is it normal for some sound to leak to the other channel when the
>volume pushed to the max with one channel input RCA unplugged?

>After eliminating one by one, now the problem points to the PreAmp. I
>have tried with all other inputs ( CD, video, Aux etc) and the result
>is the same. The appears to be some leaking to the other channel at
>high volume and High frequencies above 10khz. (too lazy to measure -
>but high pitch female voice can be heard).

>I believe the spec said something like 110db but now maybe the figure
>could be half of that.

Rather than listening to an open circuit, load the input. 10K or less
would be appropriate.

That 110dB figure seems high, but in any case, it was probably measured
with the unused input shorted.

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Anonymous
January 2, 2005 9:48:00 PM

Archived from groups: rec.audio.tech (More info?)

tchelvam@hotmail.com wrote:
> Thanks but unable to understand "load 10k".

This means attaching a 10 K resistor across the input terminals of the
unused input channel.

> What I have done was to disconnect , say my left input, and push my
> balance all the way to left with music being fed into the right
> channel.

IOW, you're basically doing somthing that is irrelevant to normal
operation.

> Strangely, I do hear my left speaker.

IME, not strange at all.

> If I reverse the cables
> than the right speaker can be heard. I tried with my two other mini
> compos and get the same result.

This is nature's way of telling you that this is considered normal.

> But I must push my volume control to
> the max or atl east to the vey very loud level to hear the faint
sound
> from the speaker.


IOW, you're basically doing somthing that is irrelevant to normal
operation.

> Is this known as "cross talk"?

Yes, its one form of it.


> Am I correct to say that most pre amp
> leaks some signal to the other channel.

They all do. If nothing else, this cross-talk can be measured.

> I have never actually done this
> before and therefore can't tell for sure if it was present from day
> one.

It no doubt was present all along, just as it was present in the other
equipment you tested.

> If I leave the balance in the centre but with one input unplugged
than
> I don't hear any music from the other channel, so it appears that
under
> normal listening level the audible "crosstalk" is negligeble.

Good call!

> I think this problem is too common.

Most people don't think it is a problem since it is inaudible under
normal operating conditions.

> Anybody out there done the same?
Yes.

> Just be careful to reset the volume.

Yup.
Anonymous
January 3, 2005 3:42:08 AM

Archived from groups: rec.audio.tech (More info?)

In <1104658592.673612.3880@z14g2000cwz.googlegroups.com>, on 01/02/05
at 01:36 AM, tchelvam@hotmail.com said:

>Thanks but unable to understand "load 10k".

Sorry, the buzzwords you used caused me to assume you had a bit more
experience.

Rather than having nothing plugged into the unused channel, connect a
10K Ohm resistor from the center pin to the outside ring. A open
circuit created by unplugging the source creates an easy path to pickup
some energy from the other channel or another input. A component
connected to (and turned on) the input presents a somewhat low
impedance (typically less than 2K Ohms) which will completely dissipate
the minute energies that you could easily hear in the unloaded input.

>What I have done was to disconnect , say my left input, and push my
>balance all the way to left with music being fed into the right
>channel.Strangely, I do hear my left speaker. If I reverse the cables
>than the right speaker can be heard. I tried with my two other mini
>compos and get the same result. But I must push my volume control to
>the max or atl east to the vey very loud level to hear the faint sound
>from the speaker.

>Is this known as "cross talk"?

Yes, this crosstalk can also come from other inputs. Often, a little of
the tuner output will leak into other sources. It is common for
receivers to switch off the tuner when other inputs are used. "Channel
Separation" is another term used in these discussions. Channel
separation is a measure of the crosstalk between left, right, rear,
etc. for a given input.

>Am I correct to say that most pre amp
>leaks some signal to the other channel. I have never actually done
>this before and therefore can't tell for sure if it was present from
>day one.

At some level all units exhibit crosstalk. One can go to a lot of
trouble and add considerable expense to minimize the cross talk. While
there may be some bragging rights associated with 80, 90, 100 dB or
more crosstalk suppression, there is little practical benefit to
channel separation beyond 30-40dB when playing typical music.

>If I leave the balance in the centre but with one input unplugged than
>I don't hear any music from the other channel, so it appears that
>under normal listening level the audible "crosstalk" is negligeble.

>I think this problem is too common. Anybody out there done the same?
>Just be careful to reset the volume.

Your unit seems to be OK, none is perfect.

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Anonymous
January 3, 2005 5:10:38 AM

Archived from groups: rec.audio.tech (More info?)

Thanks guys.

I just lost my other reply. So can I ask why the problem happens in my
preAmp and not my power Amp. When I tried with one channel unplugged in
my power amp - no crosstalk. I though preamp and power amp are
basically the same except one for controlling various parameter?
Can't similar tech implemented in both?
Anonymous
January 3, 2005 10:49:03 AM

Archived from groups: rec.audio.tech (More info?)

tchelvam@hotmail.com wrote:
> Thanks guys.

> So can I ask why the problem happens in my
> preAmp and not my power Amp. When I tried with one channel unplugged
in
> my power amp - no crosstalk. I though preamp and power amp are
> basically the same except one for controlling various parameter?
> Can't similar tech implemented in both?

The crosstalk is present in your power amp as well. However, your power
amp does not have as much gain as your preamp, and so the crosstalk
signal is not as audible.
Anonymous
January 3, 2005 4:22:24 PM

Archived from groups: rec.audio.tech (More info?)

tchelvam@hotmail.com wrote:
> Thanks guys.
>
> I just lost my other reply. So can I ask why the problem happens in
my
> preAmp and not my power Amp. When I tried with one channel unplugged
in
> my power amp - no crosstalk. I though preamp and power amp are
> basically the same except one for controlling various parameter?
> Can't similar tech implemented in both?

Cross talk and channel separation is one of those
"specsmanship" numbers that are there ONLY to impress
people into buying the equipment. In terms of listening,
the amount of crosstalk allowable before there is even
miniscule audible deterioration is SO much more than
even you're encountering that it makes the whole
excercise a waste of time. You may be hearing the
consequence of 110 dB or 100 dB or 90 dB or even 60 dB
of actual crosstalk. In fact, the amount of crosstalk
you can have without perceiving a noticeable degradation
is FAR worse than that. 40 dB is MORE than sufficient,
and the actual separation on the vast majority of the
musical source is MUCH worse than that, on the order of
20 dB.

You're obsessing over a meaningless parameter that has no
audible consequence.
Anonymous
January 3, 2005 6:16:31 PM

Archived from groups: rec.audio.tech (More info?)

<tchelvam@hotmail.com> wrote:

>Is it normal for some sound to leak to the other channel when the
>volume pushed to the max with one channel input RCA unplugged?

On a good day, LP turntables (remember vinyl?) normally have crosstalk
specs of around 40 dB, and some audiophiles think they're wonderful!

--
Len Moskowitz PDAudio, Binaural Mics, Cables, DPA, M-Audio
Core Sound http://www.stealthmicrophones.com
Teaneck, New Jersey USA http://www.core-sound.com
moskowit@core-sound.com Tel: 201-801-0812, FAX: 201-801-0912
Anonymous
January 3, 2005 9:46:42 PM

Archived from groups: rec.audio.tech (More info?)

Len Moskowitz wrote:
> <tchelvam@hotmail.com> wrote:
>
> >Is it normal for some sound to leak to the other channel when the
> >volume pushed to the max with one channel input RCA unplugged?
>
> On a good day, LP turntables (remember vinyl?) normally have
crosstalk
> specs of around 40 dB, and some audiophiles think they're wonderful!

Based on the cartridge measurements I used to make, 40 dB is about an
order of magnitude better than real world.

Giving the devil his due, there isn't much subjective advantage to
channel separation greater than about 20 dB.
Anonymous
January 4, 2005 12:54:44 PM

Archived from groups: rec.audio.tech (More info?)

In <1104747038.926716.170540@z14g2000cwz.googlegroups.com>, on 01/03/05

at 02:10 AM, tchelvam@hotmail.com said:

>Thanks guys.

>I just lost my other reply. So can I ask why the problem happens in my
>preAmp and not my power Amp. When I tried with one channel unplugged
>in my power amp - no crosstalk. I though preamp and power amp are
>basically the same except one for controlling various parameter? Can't
>similar tech implemented in both?

There are differences between power amplifiers and preamplifiers.
Crosstalk is not as significant for power amplifiers.

While they are similar "crosstalk" and "channel separation" are
different. Crosstalk is more general and could include channel
separation. Channel separation is specific and applies to crosstalk
between various channels associated with a given device.

30dB or so of channel separation is more than enough for any practical
musical listening situation, -30dB of crosstalk between TUNER and CD is
not tolerable. The other channel(s) are correleated to each other,
while TUNER and CD are not. Part of what makes humans so special is
their ability to quickly and easily destinguish between correlated and
uncorreleated sensory events.

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Anonymous
January 4, 2005 1:42:17 PM

Archived from groups: rec.audio.tech (More info?)

On 3 Jan 2005 02:10:38 -0800, tchelvam@hotmail.com wrote:

>I just lost my other reply. So can I ask why the problem happens in my
>preAmp and not my power Amp. When I tried with one channel unplugged in
>my power amp - no crosstalk. I though preamp and power amp are
>basically the same except one for controlling various parameter?
>Can't similar tech implemented in both?

You can design for minimal cross-talk. Actually, what you were
describing in your preamp, used under unrealistic conditions, WAS
minimal cross-talk. But it can be reduced. Generally, designers
don't bother.

Your power amp has less cross-talk. If you could turn it up to the
same gain level as your preamp was providing, it may have shown more.
Probably the fact that it DOESN'T offer the same gain ratio as a
preamp is a main design factor reducing perceptible cross-talk :-)
Anonymous
January 5, 2005 12:59:34 AM

Archived from groups: rec.audio.tech (More info?)

Laurence Payne wrote:
> On 3 Jan 2005 02:10:38 -0800, tchelvam@hotmail.com wrote:
>
> >I just lost my other reply. So can I ask why the problem happens in
my
> >preAmp and not my power Amp. When I tried with one channel unplugged
in
> >my power amp - no crosstalk. I though preamp and power amp are
> >basically the same except one for controlling various parameter?
> >Can't similar tech implemented in both?
>
> You can design for minimal cross-talk. Actually, what you were
> describing in your preamp, used under unrealistic conditions, WAS
> minimal cross-talk. But it can be reduced. Generally, designers
> don't bother.

Like using a passive preAmp? In my case, the preamp is actually
functioning more like attenuator. Once, I (out of curiosity but thank
god that didn't kill the speakers, though) connected directly from my
DAC to the power Amp. It was really loud. I dare not push up my my
preamp volume to see how loud because at about 12 o'clock it's enough
to have the neighbours drop by uninvited. I know the simpler way is to
measure the uout put with some meters. I no Electronic guy.

So can a pasive preamp eliminate the cross-talk?


> Your power amp has less cross-talk. If you could turn it up to the
> same gain level as your preamp was providing, it may have shown more.
> Probably the fact that it DOESN'T offer the same gain ratio as a
> preamp is a main design factor reducing perceptible cross-talk :-)
Mmmm ...both were of same make/brand.
Anonymous
January 5, 2005 6:03:47 AM

Archived from groups: rec.audio.tech (More info?)

Sorry to be imposing but I am bit blur. Care to explain in plain
language for disadvantaged people like myself.

Some thirty years ago when I listen to casette tape, I used to
encounter this "crosstalk" . But then I used a portable mini -compo and
it depends how long I play or leave the system on and occassionaly
after few fliping of switches it will be minimized or disappear. But
one thing I remember at that time, it affected my enjoyment of music
and at the time I don't know what's a high end and the best player I
knew was philips the cheapest supposed to be Sanyo. And the so called
HiFi was "Sansui".

Anyway, I don't remember hearing the crosstalk for radio, but I did get
to hear cassete and radio in any one mode, sometimes.


But now having abetter system but hardly listening to music but more
to faults.
Anonymous
January 9, 2005 2:03:25 PM

Archived from groups: rec.audio.tech (More info?)

On 4 Jan 2005 21:59:34 -0800, tchelvam@hotmail.com wrote:

>So can a pasive preamp eliminate the cross-talk?

Sure. As can an active one, if designed to do it.

But, as the level of crosstalk described is a non-problem.....
Anonymous
January 9, 2005 7:07:30 PM

Archived from groups: rec.audio.tech (More info?)

In <1104904774.077973.40070@z14g2000cwz.googlegroups.com>, on 01/04/05
at 09:59 PM, tchelvam@hotmail.com said:


[ ... ]

>So can a pasive preamp eliminate the cross-talk?

No.

In a few cases, admiditedly in bad areas, connecting a length of
speaker wire to a loudspeaker -- no amplifer involved -- is enough to
have "crosstalk" with a local radio station. The first time I
encountered this I was shocked (how could this happen?), now I'm just
annoyed, because it is usually at a customer's home and I'm expected to
solve the problem.

[ ... ]

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