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Category: VCAs + Amplifiers

Design a Eurorack “Vintage VCA” with the LM13700

Posted on April 11, 2020August 31, 2025

The LM13700 is a bonafide classic synth chip, plus it’s cheap and *still* available decades after it was originally introduced. Ok, it’s no longer the state of the art, and its noise and distortion figures are pretty poor, but that’s actually a part of its charm. It’s definitely got that “vintage sound”. So let’s have […]

Posted in Projects, VCAs + Amplifiers   69 Comments on Design a Eurorack “Vintage VCA” with the LM13700

RC Filtering for SSM2164 CVs fed from DACs

Posted on June 26, 2015August 12, 2025

I typically use the 12-bit MCP4822 DAC to produce a CV for the SSM2164 (or CoolAudio V2164, it’s the same thing) . This is a good, cheap combination. However, the 4822 produces an output of 0-4.095V, whereas the 2164 needs 0-3.3V. It is possible to use a simple voltage divider to reduce the voltage to […]

Posted in Filters, Synth DIY, VCAs + Amplifiers   Leave a Comment on RC Filtering for SSM2164 CVs fed from DACs

Single VCA crossfader

Posted on June 9, 2015September 2, 2015

There are a number of situations where it is useful to be able to crossfade between two different signals with a single control. Examples might be a wet/dry control on a delay effect, or a waveform knob on an oscillator that goes from ramp to square continuously. The simple and obvious way to do this […]

Posted in Projects, Synth DIY, VCAs + Amplifiers   34 Comments on Single VCA crossfader

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Druid code and schematics are released under a CC BY-NC-SA 4.0 license, so feel free to download and use Electric Druid code in your personal synth, pedal, or sonic blastertron 2000. Grab a copy of the schematics and tweak away to your heart’s content. If you don’t have a PIC programmer, you can order a chip from the shop. Check the legal stuff for more details.

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Electric Druid code and schematics are released under a CC BY-NC-SA 4.0 license. Please check the legal stuff for more details. If you’d like to use Electric Druid chips, code, or circuits in your commercial product, we’d ask that you buy chips from us to help support the development of further projects. We can supply programmed, labelled chips in whatever quantities you need. If this isn’t suitable, please contact us to discuss your requirements. Thanks!