Barton Full Wave Rectifier

This is the Barton Musical Circuits BMC21 Full Wave Dual Rectifier in Kosmo format. It’s built using a PCB I bought from Barton, behind a panel I designed and had fabricated. It’s a kind of wavefolding circuit. An input waveform is AC coupled, a DC bias is added, and it’s rectified, so anything below 0 […]

Kassutronics Dual LFO

Kosmodrome has a low frequency oscillator, the MFOS voltage controlled LFO, with a modification to give it a sync input. A pretty powerful module. I don’t really need more such fancy LFOs but a couple of basic, non synched, non voltage controlled LFOs would be useful. So this is my new Kosmo format dual LFO. […]

Voltage controlled all pass filter

An all pass filter sounds rather like an in joke: A filter that passes all frequencies without attenuation. A piece of wire, in other words? But no: Filters change not only amplitudes in a frequency dependent way, but phases as well. An all pass filter just specializes in the latter. Sine waves far below the […]

Yet another sample and hold

This is a Kosmo format version of René Schmitz’s YASH sample and hold. Sample and hold is something used in a lot of contexts other than / more commercially important than synthesis, so there’s such a thing as sample and hold ICs that are readily available. This uses the LF398 chip. All Schmitz’s circuit does […]

CGS (Ken Stone) Active Real Ring Modulator

This is a ring modulator in Kosmo format. No, really. A real ring modulator. There are lots of “ring modulators” out there that are in fact no such thing. They have similar behavior, and may arguably be better in some ways, but they’re more properly called four quadrant multipliers or balanced modulators or something, whereas […]

ARP 2600 (-based) envelope follower

This is an envelope follower (EF) module in Kosmo format with mic and instrument preamplifiers. I looked, in simulations and on the breadboard, at several envelope follower designs (you can read about some of that by following the envelope follower tag) and ended up deciding to go with a design based on the ARP 2600 […]

How to vactrol

Look around the synth DIY world and before long you’re likely to find a circuit containing something like this: This is an attempt to give voltage control to a circuit, using a vactrol. A vactrol is a light source (classically a little neon or incandescant light, but these days an LED) and a photoresistor butted […]

Op amp tester

I built a stoopid little op amp tester. Turns out those two TL074s I assumed were fried after I reverse powered them seem to be okay. Good enough to light LEDs anyway. https://gitlab.com/rsholmes/opamptester

Video: March of the Modules of March

IR Input

I’ve built my modification of the Barton Infrared Input. It’s pretty much as I breadboarded it with a couple of trivial exceptions. One is that I wanted to change the direction of the gate sensitivity/threshold pot… but I managed only to mirror it along with its inputs in the schematic, so it came out the […]