Pooh Bear wrote:
Would be interested to know what Q101 and 102 are though.

They are 'KTC2240BL' (the component list is on the bottom left of the
schematic).

As for measuring the noise properly, I'm afraid my methods are probably
next to useless ! All I have to gauge it by are my ears, and my
extremely un-scientific 'soundcard method'. i.e. I'm plugging the
output from the mixer directly into the line-in on my PC's soundcard
and measuring the signal level from within an audio editor (Cool Edit
Pro). As none of this is really calibrated, the numbers are probably
meaningless, but the differences between the numbers should be ok.

e.g. -
with the cable to the soundcard shorted, I get -76dB showing.
with the cable connected to the mixer output (but nothing assigned to
the output and all faders to zero), I get -71dB.
with a microphone connected to channel 1 (heavily wrapped up in cloth
in a silent room - as I have no resistors lying around !), ch1 fader
and master fader set to 0dB, pad switch OFF, input trim ZERO, I get
-68dB
As above, but with the input trim set to max gain, I get -37dB

Like I said, I don't know if any of this is helpful, but it's all I can
offer right now ! :-)

Cheers,

Kev.