Measuring Noise Levels (S/N)

[Bob Zimmer]

It's been a cold winter in my basement and I'm starting to get back into
building now that it is warming up here on the East Coast!

I've been experimenting with some VCA circuits using various types of
op-amps.  What I've found is that I really can't tell much of a difference
in noise levels between say a TL071 and a NE5532.

If I'm trying to match the performance (or at least get close to) of a
CEM3330 VCA chip (100 db S/N), how can I measure just what the noise floor is???

Also, I've seen headroom measurements on VCA's vary between 55 db and 80 db.
I'm assuming that this is measuring the voltage difference between the
strongest signal and dead quiet in what will pass through the VCA. What is
an appropriate target for a first rate VCA and how does one calculate this?

I'd appreciate any advice you folks can offer!


  >=== Bob Zimmer -- Philadelphia PA ===<
  >=== bzimmer at voicenet.com          ===<