Current Controlled Amplifer Article at GEO

[R.G.]

I finally got time to write down some ideas I've had rattling around for a while. They're up in "new at GEO".

I finally got an LM13700 to behave reasonably well under fast gain changes. It's not perfect, but neither is anything else I've tried for that. I put together a schemo for a Current Controlled Amplifier (CCA) that has a gain from essentially off to about 2, along with the necessary input buffering. The rest of the article is some things you can do with that:

- a manual volume pedal
- a tremolo
- a stereo volume/pan pedal
- a stereo trem/pan
- a two and a four channel morpher for effects loops

Coming is circuitry for an attack delay and a few others as I get time.

[aron]

Very nice!

Looks fairly simple.

Thanks!

Aron

[Peter Snowberg]

Very nice article R.G. !

Another gem.

Take care,
-Peter

[Tim Escobedo]

Interesting article, R.G.

Did you use the 386 trick for ref. voltage? The LM13600/13700 kinda frustrated me a bit running off 9V until I realized they seem to like a real bipolar supply. Or more than the average resistive divider.

[amz-fx]

Nice article.  Is the last sentence under Application 1 cut off and missing a couple words?

regards, Jack

[R.G.]

Did you use the 386 trick for ref. voltage? The LM13600/13700 kinda frustrated me a bit running off 9V until I realized they seem to like a real bipolar supply. Or more than the average resistive divider.

Yes, the board layouts I'm doing will have the 386 for a reference. The OTA circuits need a high current Vref because they feed their output current back into the reference, so it has to be rock steady. An opamp reference works too, if you have an extra opamp on the board otherwise unused.

Nice article. Is the last sentence under Application 1 cut off and missing a couple words?

Thanks. Yes, it's probably missing a word or two. I did the whole thing in Corel Draw, text included, and Corel Draw does a worse job on rendering text than it does drawings. I'm not happy with the text rendering at all, so it needs another pass. If your text box is not the right size, the text is cut off because the box is held to a strict size, consistent with the "drawing" focus of the program.