John Woodgate wrote:

I read in sci.electronics.design that Pooh Bear rabbitsfriendsandrelati
wrote (in ) about
'Reducing hiss by changing op-amps ?', on Sat, 19 Mar 2005:
Winfield Hill wrote:

Don Pearce wrote...

The mic inputs are discrete - you need to be looking at Q101 and
102 and so on. I'm presuming the line level stuff is quiet enough.

Right, as John and others have also said. Changing the opamp won't
make any difference for the mic preamp stages.

Well, actually it *will* at lower gains where the transistor noise no
longer dominates.

It would make a difference (possibly marginal) to the *noise output* but
not to the mic pre-amp stages themselves, since they don't include any
op-amps.

But they do !

The mic pre consists of a differential long-tailed pair followed by a
differential op-amp configuration to make the signal 'single ended'. The
contribution of the op-amp at low gains normally dominates the noise output
of the mic pre.


Besides the 4558 is a POS for audio in every possible way.


Here we go again! These legacy op-amps are quite OK **if used within
their limitations**. They are still used today in large quantities.

I think even the DJ mixer fraternity ( the ultimate cheapskaste
manufacturers ) have pretty much junked them now.

I wouldn't agree that a 4558 is 'ok' for audio.


Graham