11 things to know about Control
18 HP 24 mm deep 52 mA Designed June 2020
Available from Thonk Videos Modular Grid Request Design Files Schematic
- After spending a lot of time working on smaller and smaller projects, I realised that many Eurorack synths were missing something critical: controls that are big enough to be fun.
- I wrote a longer piece about Human-Sized Musical Interfaces, touching on NASA guidelines, the cult of vintage test equipment and DJs suffering from Hot Knobs.
- Control is an absurdly simple module: Four big knobs that output voltages. Connect those voltages to modules, and you have high-precision, intuitive control. Connect those voltages to several modules, and you have interesting, repeatable confusion.
- The first two channels (top two knobs) are also attenuators if something is plugged into the leftmost sockets.
- The voltage on each channel can be 0–5v (middle), 0–10v (up), or -5v to +5v (down). When using a channel as an attenuator, keep it in 0–5v or you’ll get weird gain or offset (which you may want).
- There are two extra outputs. Change outputs just the changes as they happen. If a knob is turned quickly to the right, it will output a little burst of positive voltage. If a four-handed performer turns all four knobs quickly anti-clockwise, it will output a chunky pulse of negative voltage. Patching Change into an input creates a primitive clock.
- Diff is a difference rectifier, inspired by NonlinearCircuits, but with a slightly different circuit. It compares the difference between 1&2, and between 3&4, and finally outputs the difference between those two differences. The aim was to create a bumpy, unpredictable voltage between 0 and 10v. It’s not random, but it’s not easily predictable, either.
- Each knob has its own bi-colour LED to provide visual feedback on how much voltage is being output. There are also LED indicators for the Change and Diff outputs.
- And that's just about it. The circuit isn't designed to be super precise. It works best when you patch into a bunch of points in a complex patch, then just sit back, listen, and make small (or big) movements with the knobs.
- The pots themselves are a bit special: high quality TT Electronics P260T – as used in SynthTech modules and many 5U synths. They have steel shafts bolted to the front panel and they feel great.
- It's a relatively simple build - all PCB components are pre-soldered SMD, so the assembly is mainly LEDs, pots and a slightly fiddly mechanical process. Watch me building a kit below.