John Woodgate wrote:

I read in sci.electronics.design that wrote (in
.com) about 'Reducing
hiss by changing op-amps ?', on Sun, 20 Mar 2005:
Not strictly true - I can notice the hiss *more* when I turn up the
input trim. The original problem is that the desk is too hissy - when
used at *any* level :-)

It's used on stage for my band as it has better EQ (not to mention more
inputs !) than our previous PA head, and since we made the switch we've
noticed a distinct increase in hiss coming through the PA speakers -
which is coming from the mixer. I just wanted to see if I could reduce
the noise level as a lot of our numbers are quiet-ish and no doubt the
sound could be improved by some hiss reduction.


Then change the mixer stage op-amp to a TL072. That is a major source of
noise of the type you mention.

The 072's not really that quiet by modern standards, John.

Without a thorough examination of the gain structure and thermal noise
contributions of various stages it's tricky to recommend specific areas that
need the most attention in terms of substitution..


Graham