This is the bottom half of Betsy. This half includes all of the synth modules as well as a hacked Syntechno TeeBee303 that is really only being used for it's 4-channel MIDI->CV converter (though I do think it does an excellect 303 sound). The power supply is also in the bottom - in the area behind the cable-storage tray.

The black module in the top row is the first module I ever built - an Electronotes Tri-Square VCO that can be found in either the Electronotes Preferred Circuits Collection, or in the book Electronic Music Circuits by Barry Klein. Hearing that triangle when I first fired it up was pure joy for my ears. I kept my original hand-lettered front panel - kind of like my first dollar bill.

The TeeBee303 in the middle was a pretty deep rack-mount module, but most of it is empty space. It just has two small circuit boards - one on front and one in back. I took off the top, bottom and sides and mounted the front and back to the front and back of the modlular. I also put banana jacks in the faceplate and wired them to the 1/8" MIDI->CV jacks in the back. The TeeBee runs off of a 0 / +15v power supply, so I simply wired it up with my synth's PS.

The modules are made from Paia FracRack face plates. I wasn't impressed with the mounting rails for the frac-rack system (though I am using them with my new modular) - and I wan't each row to be longer than 19", so I made my own horizontal rails from aluminum bars 3/8" x 3/4" x 20". Drilling and tapping the holes for machine screws. It's very solid, but was a pain ain the neck to build...

Betsy's now been partially dis-assembled as she donated organs to Spunky - but she's still got most of her stuff and is still in use.

Moodule Listing:

(LS = left side, 1S = 1SpaceWide, 2S = 2SpacesWide, RS = right side, "space" = 1.5")

Top row, left to right;

(LS) Dual external input pre-amps - one with an envelope follower.

(1S) Dual VC-Slew (or lag or glide or portamento) module.

(2S) Tri-Square VCO (1v/oct, linear FM input, PWM square out, saw, out, tri out, and sine out)

(2S) Tri-Square VCO

(2S) State-Variable Filter with manual x-fade between LP and HP outputs

(1S) VC-Waveshaper

(1S) Ring-mod, Sample/Hold, Noise Source

(1S) VC-Waveshaper based on VC-distoration

(1S) ADSR

(2S) 2 Channel Mixer with VC pan and VC gain for each channel

(RS) Banana -> 1/4" converters

 

Middle row, left to right;

(LS) Nothing.

(1S) VC LFO. Same as a tri-square VCO with a bigger timer cap and less front panel features.

(2S) VC Evelope Generator / Slew Module - similar to one half of a Serge Dual Slope Generator

(1S) 3 Channel CV mixer with offset

(1S) Ring-mod, Sample/Hold, Noise Source (same as in top row)

(2S) Dual state variable filter based on a CEM3350 filter chip.

(1S) ADSR

(1S) VC-AR

(1S) Another VC LFO. Same as a tri-square VCO with a bigger timer cap and less front panel features.

(2S) 2 VCAs + 1 VC x-fade. Built around a single SSM2024 quad VCA IC.

(RS) Dual manual voltage utility module. Outputs two voltages with -5v to +5 range, also has ground, +5v and +15v jacks.

 

Bottom row, left to right;

(LS) Fancy pre-amp and envelope follower.

(1S) PLL-based frequency to voltage converter with 1v/oct output. Doesn't work too well.

(2S) VCO faceplate - circuit wasn't built at the time of this picture.

(2S) Tri-Square VCO

(2S) State-Variable Filter with manual x-fade between LP and HP outputs

(2S) Moog Ladder Filter (4-pole LP)

(1S) VC-Waveshaper based on VC full wave rectification.

(2S) VC Evelope Generator / Slew Module - similar to one half of a Serge Dual Slope Generator

(RS) Was going to be a dual gate delay, but I never got around to building the circuit - didn't need it with the other EGs.