Dc controlled stereo volume

[Marcvv]

I am looking for a schematic for a dc controlled stereo volume to control the master volume of a rack guitar system.
I found http://www.brainmapping.org/Steel/VCA.html but the ssm2018t seems hard to find.
I know the Anderton volume retrofit but reading the posts about it it might not be the quailty i want at the end of the chain.
i am looking for suggestions.

Thanks

[R.G.]

There is a stereo volume control application circuit in the LM13700 datasheet.

[Marcvv]

Yes of course. Thanks.
I forgot about http://www.geofex.com/Article_Folders/VCA%20Applications.pdf.
Will this be ok at the end of the chain? I am looking for full range specs as I am using it for both electric and acoustic guitars.

[R.G.]

Will this be ok at the end of the chain? I am looking for full range specs as I am using it for both electric and acoustic guitars.

Depends on how big the signal is at the end of your chain. Some people have it at guitar level, which is where that was intended to go, and some people use several volts of signal from booster pedals and such. That won't work as well. But you can pad it down by making that 10K resistor before the input bigger. With only 9V powering the opamps and/or LM13700, you'll be limited in how big an output you can get as well.

[ashcat_lt]

But if you're pushing that much voltage, you must be looking for distortion, right? 

[Marcvv]

Anyone made a layout, pcb or perf, by chance?

[electrosonic]

There are ICs designed for that purpose. Not especially cheap though - check out the Design Notes on the That Corp. website.

http://www.thatcorp.com/datashts/dn116.pdf

Smallbear sells the 2181B IC for $6.75 (and you will need two of them for stereo)

[PRR]

THAT 2162 is a dual VCA; ProFusion sells them at GBP £ 3.21 (about $6.33 USD).

Use the same auxiliaries as in the app-note cited above.

Input impedance (either way) is kinda low for guitar-chain use.

You probably do NOT want 40dB gain.

Changing the input R2 "20K" to 680K makes impedance more guitar-friendly and reduces maximum gain to a more friendly 10dB.

If you like to roll-yer-own, a current-steering VCA is a functional and un-fussy design.