Almost ten years ago I built the L-1 Stereo VC Mixer. That was quite an involved build! But just now I got a hankering for a Quad VCA and went looking for a DIY module. Turned out that SynthCube had one of these Quad VCA Mixer DIY bundles, the same as offered on the L-1 website. This bundle includes the PC board with SMD pre-soldered and the front and back panels. I ordered from SynthCube. I was so enthusiastic that I went head and ordered all of the remaining parts, well over $100. The next day SynthCube informed me they made a mistake and it was actually out of stock. Oh no!

Note the white knobs. The black ones were out of stock at Small Bear/SynthCube. I kind of like the white knobs.

So I went ahead and sent payment to L-1 for the kit. Luckily, they had it and took my order. Alex at L-1 has always been very helpful. The kit came today and I built it in about three hours.

I followed my practice of soldering the chips, rather than using sockets, so long as the PC board is high quality and can withstand a chip replacement if necessary. (In my recollection I have only once found a brand new through hole IC to be defective and needing replacement. That is out of hundreds of chips over the years.) I used organic, water washable flux solder for this initial board population. I had to use TL072 chips in the audio path, since the preferred OPA2604 was not available.

The hardest part was finding four M3 hex nuts! I have tons of M3 screws, but I had to scrounge to find four nuts.

This and other L-1 modules typically cover the back of the module with a thick aluminum panel with a cutout for the power cable. The back cover protects the circuitry better than almost any other eurorack module I have seen.

The Quad VCA/Mixer fired up no problem and was very easy to calibrate for unity gain. I am looking forward to putting this Quad VCA into action.

The response curve is between linear and exponential and sounds great.

Control voltage in requires +5V for unity gain. When using the CV in, the knob acts as an attenuator, which makes it easy to dial in unity gain for envelopes greater than +5V. In addition, up to +10V may be applied, resulting in 2x unity gain, up to a maximum of 20V p-p, where it then clips. This VCA can amplify!