DIYbanter - View Single Post - Reducing hiss by changing op-amps ?

wrote...

I've just been playing around with the desk and have found that the
biggest source of noise does seem to mic preamps - If I sweep the input
trim pot next to the 20bD pad switch (sorry - can't work out where it
is on the schematic !), then I get a massive change in background hiss
- 30dB's worth !

That's just because you're changing the input-stage gain. Try making
the measurement with and without an input short connected, as per
my other post. You could see a 25dB change that way, according to
my calculation.

--
Thanks,
- Win