moog VCF in vintage enclosure

Over the course of the past few years I've owned two Moog Prodigies. I got the first (keyboard-less) one about six years ago and modified it extensively. Eventually I sold it to buy the second one, which is covered in an previous post.

Of all the Prodigy's features, I've really just missed the warmth of the transistor ladder filter. But I've been so completely satisfied with the EML101's sound and versatility in every other regard that I decided it would be best to build a VCF module based on the Moog design.

I've never had much discipline for prototyping or PCB layouts so I arranged and soldered the parts on perf board and let the schematics guide me as I went. It's a challenging aspect of my electronics work.. but it's a good exercise in creative problem-solving.

While checking local thrift shops for an enclosure, I found this old electric shoe-shiner. The 'Regina'-brand "Electric Shoeboy." It originally had an industrial-type motor inside and rotating brushes protruding from each side.

After removing the motor and the shaft, dremmeling the case, and cutting, super-gluing and epoxying aluminum to cover the side holes, I had this finished enclosure! (The last image in this post was found on google to show what this unit looked like before modification.)

I based my circuit on yusynth's plans, but changed a few component values for a greater range of control. I also scaled the keyboard CV input for the EML101, with a SPDT switch to select between 1.2V/octave and 1V/octave.

Here are a few sound samples:

- moogvcf1.mp3
- moogvcf2.mp3
- moogvcf3.mp3
- moogvcf4.mp3
- moogvcf3.mp3
E-mail me if you'd like me to build a synth module in an enclosure of your choice!

moog (modular) prodigy

This is a truly unique Moog Prodigy! I purchased it on ebay- broken- about a two years ago. After restoring all of its original functionality and its original appearance, I realized it held a lot of potential for interfacing with other modular equipment, including my EML101.

Luckily, this was the later model with the Sync Input, VCF Cutoff In, Oscillator In, Keyboard In/Out, and S-Trig In/Out.

I added a Gate Input, Gate Output, Oscillator 1 Output, Oscillator 2 Output, Mixer 1 Input, and Mixer 2 Input.

The 'Mixer Inputs' come before the Mixer potentiometers, so (one or two) external signals can be injected, attenuated, and mixed.

The Oscillator Outputs are interesting, too, because they can be used as effect send/returns. For example, one oscillator can be run through a phaser or vibrato effect, while the other is left dry.. and they both run through the VCF and VCA.

In lieu of drilling and adding a VCF FM control pot, the Oscillator Output jacks make it possible to patch the audio frequency CVs to the VCF CV Input with a simple attenuator in between.

I built an additional unit to serve as the Prodigy's second LFO, Noise Source, and patching Attenuator.

Due to financial constraints, I had to sell this Prodigy on ebay about a year ago. I vowed to one day build a clone of its VCF (so the EML101 could impersonate the Moog sound).

Here are some sound samples (recorded with the additional module for modulation, noise, and/or patching.. and some spring reverb):
- prodigy1.mp3
- prodigy2.mp3
- prodigy3,mp3
- prodigy4,mp3
- prodigy5,mp3

E-mail me if you'd like to have your prodigy modified similarly!

modified poly-800 mkII [number two]

This Poly-800 mkII features the same modifications as my previous Poly-800, but it also includes the 2/4-pole filter switch.

The 2-pole VCF output sounds wonderful. If Korg (25 years ago) had me helping to make their big decisions, I would definitely have argued that the filter output must be switchable between 12 and 24 dB/oct.. I also wish they'd added this option on the DW-8000.

My control layout and labeling were also improved on this Poly-800. Additionally, the external input can now be used regardless of the setting of any parameter when the 'Noise+EG3' switch is turned "off." This causes the third envelope to have no effect on the external input level. So, to solo the external input, parameters 17 and 27 (Osc. 1 and 2 levels) simply need to be turned down.

When using my EML101 (or the Axxe I'm modifying for a local customer) to generate triangular LFOs, random S/H, or even envelopes to control the Poly-800's filter, I realize how lively the it can really sound. It takes on a much more antiquated and nuanced character. I think the 800's modulation generator just doesn't sound as smooth as a real analog LFO.

Recently, Kate and I have recorded a lot of material using the Poly-800 for its abilities as a synthesizer, but also as an effect processor for guitars. It appears on some of the new hushes and briefscenes songs.

This Poly-800 mkII was sold on ebay. ..including that cool original case!
I wish I'd kept that!