Q:Channel Separation problem.

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
15 answers Last reply
More about channel separation problem
  1. 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.
  2. 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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  3. 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.
  4. 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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  5. 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?
  6. 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.
  7. 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.
  8. 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
  9. 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.
  10. 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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  11. 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 :-)
  12. 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.
  13. 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.
  14. 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.....
  15. 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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