Hi,

I tried the RMAA audio analyzer program on my soundcard (ST Audio
DSP24 Value) using line-in to line-out through the Behringer UB1002
mixer (connecting to tape-in and tape-out). The result was quite
good, with very low noise level. But looking at the Stereo Crosstalk
plot, I saw something quite strange. Crosstalk was fairly low all the
way from 30Hz-1KHz (below -90dB), but then it rised linearly (in
logarithmic scale) from -94dB at 1KHz to -72dB at 20KHz. It didn't
happen when I did a direct loop-back test, which kept stereo crosstalk
below -90dB all through the spectrum, so it must be the mixer that
added this peculiarity.

Is this normal in any mixing board? Would that level of crosstalk be
audible and affect the sound coming through the speakers? I guess it
would lessen the soundstage/stereo image, or worse, make the sound
field positioning imprecise (or unreliable, e.g., instruments moving
left and right when played at different octaves) due to different
levels of crosstalk at different frequencies.

The last question is: Should I concern myself with the issue? Maybe
it's not much of the problem, or you may have a suggestion as to how I
could correct it.

Thank you very much in advance.
Poonna

In article writes:


I tried the RMAA audio analyzer program on my soundcard (ST Audio
DSP24 Value) using line-in to line-out through the Behringer UB1002
mixer (connecting to tape-in and tape-out).

Crosstalk was fairly low all the
way from 30Hz-1KHz (below -90dB), but then it rised linearly (in
logarithmic scale) from -94dB at 1KHz to -72dB at 20KHz. It didn't
happen when I did a direct loop-back test, which kept stereo crosstalk
below -90dB all through the spectrum, so it must be the mixer that
added this peculiarity.

Is this normal in any mixing board?

Crosstalk tends to increase at high frequencies (where it would
be nice if it didn't) and I would expect that reducing crosstalk is
one of those things that's done better in more expensive mixers. It
has a lot to do with care taken with shielding, grounding, and power
supply bypassing.

Would that level of crosstalk be
audible and affect the sound coming through the speakers?

Probably not. Play something at a comfortable volume, then reduce it
by 72 dB (you'll probably need to use your DAW software, not a knob on
your mixer) and see how loud it sounds. That's the amount of crosstalk
you have.

The last question is: Should I concern myself with the issue?

Not unless you bought one of those $10,000 Behringers. G


--
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However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
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and reach me he double-m-eleven-double-zero at yahoo

Dreamist wrote:

I tried the RMAA audio analyzer program on my soundcard (ST Audio
DSP24 Value) using line-in to line-out through the Behringer UB1002
mixer (connecting to tape-in and tape-out). The result was quite
good, with very low noise level. But looking at the Stereo Crosstalk
plot, I saw something quite strange. Crosstalk was fairly low all the
way from 30Hz-1KHz (below -90dB), but then it rised linearly (in
logarithmic scale) from -94dB at 1KHz to -72dB at 20KHz. It didn't
happen when I did a direct loop-back test, which kept stereo crosstalk
below -90dB all through the spectrum, so it must be the mixer that
added this peculiarity.

Not peculiar. You jam all thet stuff in a small case and you don't use
individual shielding on each section or channel strip and you don't use
shielded wires for the buss, and you get capacitive coupling between
channels. This problem is more apt to happen at high frequencies.

You skimp on supply decoupling, and you get signal from one channel coupling
into another through the power supply. This problem is more apt to happen
at low frequencies.

Is this normal in any mixing board? Would that level of crosstalk be
audible and affect the sound coming through the speakers? I guess it
would lessen the soundstage/stereo image, or worse, make the sound
field positioning imprecise (or unreliable, e.g., instruments moving
left and right when played at different octaves) due to different
levels of crosstalk at different frequencies.

This is typical of cheapie single-board consoles. This is one of the reasons
why professional mixing consoles are modular; in part it is so that the
individual modules can be shielded and not interact with oen another.

The last question is: Should I concern myself with the issue? Maybe
it's not much of the problem, or you may have a suggestion as to how I
could correct it.

You can't correct it without spending a lot more money on a real console.
So don't worry about it since you can't do anything about it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Based on my experience with my amps and RMAA, it is not the mixer but
the cable raised the crosstalk above 1KHz. See my RMAA tests he

http://www.fixup.net/products/benchmarks

And you can easily see at the last graph of below link, what the cable
does to the crosstalk at high frequency (exactly what you found):

http://www.fixup.net/products/benchm...MU1212M3ft.htm

The cable is a 3-feet long RadioShack gold series. If I use very short
cable (shorter than 6 inches), then there is no such a problem. The
problem is, I have to use long cable; otherwise the amp must be very
close to the computer and get lots more noise.