[sdiy] HF Trim in Expos

[Rob Keeble]

Hi,
I am building an E-mu modular VCO from 1973 and I need some advice on the
expo generator circuit.

The HF trim uses an Op Amp and needs a resistor of unknown value to be
selected. I'd like to use a trimmer to make it much easier to set up the
VCO. Can anyone advise on a suitable circuit? The link below has a picture
of both the original circuit, and a possible solution from the E-mu Audity,
which uses the same LM394. Any reason why I shouldn't use the Audity design
or do I need something a bit different?

Any views or ideas most welcome! I was also thinking of using the SSM2210
rather than LM394.

Many thanks in advance - rob

http://www.emulatorarchive.com/AM/expos.jpg

www.emulatorarchive.com