Sneak-Thief's DIY Modular Synth

June 2011: The 8th Rack

What is a Klee sequencer?

It's a dual 8-step or single 16-step sequencer where the voltage of whichever steps that are enabled with a switch can be summed to the main CV output.

So imagine a step sequencer where each time it steps, multiple lights can be on at the same time instead of just 1 out of 8 or 16.

When paired with potentiometers that are tuned to specific chromatic intervals, the output is from another planet and is incredibly musical.

After having the parts to complete my Electro-Music / Scott Stites Klee sequencer for a while, the big issue was coming up with a solution for cutting slits for the sliders on the front panel. I finally tried out a crazy idea involving a metal cut-off/sanding disk in a circular saw. The results were very good.

Of course it would have been much simpler to use rotary potentiometers but having sliders for each step makes the Klee so much more enjoyable to interact with when performing.

Even the most unguided and random live tweaking can lead to lovely results:

Current modular setup:

- The 7th Rack

I prefer using one panel, Serge-style - saves a lot of trouble of getting individual panels cut.

This rack has a mankato quadrature filter, 2 wogglebug #3's, tellun neural agonizer (dual spring reverb), korg triple-resonator and a fonitronic 5-channel mixer.

(Click the thumbnails to see the full images)

The wiring looks pretty messy right now, but it will all be tied down all nice and neat. The 2 reverb tanks are for the tellun neural agonizer and will be mounted on the back of the rack.

- DIY Modular Synth Part 6: The End?

Here are some boards that are begging to be stuffed:

Row 1: tellun neural agonizer (dual spring reverb), korg triple-resonator, mankato quadrature filter
Row 2: gssl with 2 hi-pass filters, my 3rd SN-Voice, Nite EQ-3D & psu's (sooo cool!)

The final pieces of the modular are almost ready. I guess there are going to be 3 last racks. One will have a GSSL "Ultimate" version compressor alongside a stereo Nite EQ 3D clone. One of the racks will house a Scott Stites Super Klee sequencer, and finally the last rack will have the Neural Agonizer, Korg PS-3100 resonator clone, Magic Smoke Mankato Filter.

The only problem that I foresee with this being the supposed "end" of my modular build is that I've got a 3rd SN-Voice, a Blacet Frequency Divider and possibly a soon-to-be-aquired Wave Terrain oscillator, all with no home. Man, that's almost a whole other rack's worth of modules. Will it ever end??

- DIY Modular Synth Part 5: Passive Mixer with FET preamps

What good are all these audio signals without a decent mixer? How about a clean sounding passive summer, with an aux bus thrown in for fun?

  1. 8 channels with volume, aux send and panning knobs
  2. These 8 channels sum into a L/R bus
  3. This L/R bus goes into a simple 16 channel passive summer
  4. The other 14 of these L & R channels have jacks on the front
  5. All channels sum into two FETboys preamps

- Based on NewYorkDave designs:

Balanced Passive Mixer
Basic Op-Amp Mixer

(courtesy Prodigy Pro forums)

- DIY Modular Synth Part 4: CGS, Oakley & Papareil

Two more modular racks were completed here, with lovely toys such as octave dividers, lag processors, filters, comparators, burst generators, and LFO's.

The CGS Bi-N-Tic (which is also a great VCO) makes some of the most unique sounds I've ever heard from a filter. I remember giggling with glee while twisting the frequency pot and reaching that point on the filter which alwasy goes "POP". Great stuff.

Another killer CGS board is the Synthacon. It's so wet and grimey - definetely the most vintage sounding filter on my rack.

I'm disappointed to say that I still haven't managed to get my Polivox filter clone working. I was looking for some UA776 chips for this and was instead sold the supposed equivalent, LS776. Another diy-er claimed that he got his working fine with these chips, but I can't seem to get anything out of this board. Hmmmm.

- DIY Modular Synth Part 3: Thomas Henry / Scott Stites SN-Voice

The Texas Instruments SN-76477 Synth-on-a-chip had fascinated me for quite a while and I was putting together some ideas of how to build one. Many a diy-project had been designed around this chip in the last 30 years, but along came the brilliant Thomas Henry and gave it full 1V/Oct control ...the venerable SN-Voice was born and I was hooked!

I slapped together a twin SN-Voice based on Thomas Henry's design onto proto board (ack!) and helped inspire the creation of State Machine's SN-Voice PCB, which has since sold over 200 boards. My version is still unique though because of dual-555 timers which I used to drive the mixer logic inputs of the SN chip. This allows for very strange modulation capabilites, over and above the weirdness provided by the SN chips themselves.

- DIY Modular Synth Part 2: ASM-2

I had been eyeing Tom G's Wildcat II Modular synth for a while, but decided that the uncertainties surrounding his designs weren't worth the hassle. The ASM-2 had a nice lineage and offered tried-and-true circuits - although tricky at times to figure out wiring diagrams, everything worked perfectly and Elby Designs provided great support during the build.

Also included in this build were Ken Stone CGS modules and a uCapps MIDIbox CV 8 Channel Midi-CV converter

- DIY Modular Synth Part 1: Blacet Rack

My first foray into the addictive world of DIY-modular synthesis started with a beautiful little rack from Blacet Research.

July 2007