Thanks, I appreciate that!
I have some devices laying around that were used in the Boonton modulation
meters, and I also have some that Krohn-Hite used in some of their audio
oscillators. These were Wien Bridge designs that used these devices instead
of the old light bulb in the feedback network. I guess I could do it with an
FET. I do have a schematic for a regenerative preamplifier laying around,
but I haven't put much effort into it. I also have a schematic for the
Quantum Loop preamplifier, but I consider it the designer's intellectual
property; henceforth, I need to come up with my own design as a matter of
ethics.

Pete

wrote in message
oups.com...
Pete:
I have seen very linear opto-isolators in a end, custom made
AD converter. Sadly I couldn't get a diagram or even pop the
cover to study the magic. A Advark like USB audio capture
device that had the audio input completly isolated for hum/noise
control. It used 6 "D" cells that where supposed to run it for at
least a year. It was very clean, 24 bits. I hoped we would buy
several. Too pricy for our budget.

I will check around and see if any one remembers the make.

Terry