So I am closing in on imminently being able to release something I have been working on on and off for a couple years, what I have dubbed the "MG-1 ModEx" expansion/mod kit for the "Realistic Concertmate" Moog MG-1. To my knowledge, this might be the "most extreme" analog MG-1 mod design ever, um, presented, and I have particularly designed it for use with Eurorack and other modular gear, with 3.5mm jacks for all inputs and outputs, all inputs and outputs buffered and all inputs attenuated and capable of accepting positive and negative CV for maximum modular compatibility.
What I think are the two most important features that it offers are:
1) *Fully Independent* 1V/octave tracking pitch control for each of the two oscillators. I have done this by adding a second, fully independent tone source CV summer/scaler for Osc. 2. With an external sequencer or keyboard, this makes it a para-duophonic synth! You can play chords with one hand, send in a bassline from a sequencer and play a lead with the other hand. Oscillator 2 can also track the keyboard normally.
2) a second LFO with two waveforms, triangle and square, simultaneoulsy available at separate outputs. This LFO has a very wide frequency range.
I am awaiting polycarbonate panel overlays from Cubbison, design shown above (basically the same material as the original).
The PCBs are done:
Other features include:
- Modulation input for “Polyphony” (organ) section with depth control– add vibrato or something weirder
- Transpose control for oscillator 1
- Oscillator 1 individual high amplitude output to use as a modulation source
- Keyboard bypass switch for oscillator 2 – this allows you to, for example, either have the MG-1 keyboard transpose your incoming Sequence/arpeggiation, or have it be completely free-running while you use the keyboard for other things, or just set it as a pedal tone (drone)
- CV input depth control for oscillator 2 allows you to also just use incoming pitch CV for modulation if you want
- Pulse width modulation input with depth control for each oscillator. Pulse width modulation depth pots become direct pulse width control when no modulation source is plugged in.
- Additional filter CV input and depth control (modulate the filter with a fast LFO and a slow LFO at the same time!)
- Gate/V-trig input for envelope (V trig to S trig conversion).
- Envelope CV output (send it to PWM! Send it to Oscillator 2 and make a sync sweep!).
- Multi-trigger generator with on/off switch. Under normal circumstances, if you are holding a chord with the polyphony and trying to play a melody, for example, the MG-1 would only trigger its envelope on the first note. Multi-trigger allows it to retrigger with every key pressed– but you can also turn it off if it’s not helpful for what you’re playing.
- The option to also add a little separate PCB I make called "Universal Basic Input" to allow for output-input feedback and patching in of external signals into the pre-filter mixer. What this does is normal the output signal to a jack which is fed through an attenuator so it can be turned down to nothing or way up for crazy feedback; then, external signals can be plugged in and when using external inputs there is an optional level selector switch (line level vs "hot" for Euro level raw oscs etc). This is a little board with just a jack and single pot (and attenuator circuit) which is mounted into the rear panel and secured by just the control nuts.
A couple demos of the second prototype. A photo of the first one I did is in my user icon!:
I will definitely record more (and with better audio) when I make a nice looking one with the new overlays!
My guess is that the kit would be somewhere around $200-300 (that would be including all parts, so less if you just wanted to buy the PCB+overlay) but I haven't priced it all out yet.
Now here's the thing. The mods involve 18 op amps and add 7 pots, 12 jacks, 2 switches, and an LED to the panel, which requires connecting *54 NEW WIRES,* many of which have to be fed through the panel PCB by drilling small holes in it (I know this sounds nuts but there really is no other way, the panel PCB really does fit too snugly to add a lot of wires running across it and still be able to fit it into the panel). I set up the mod PCB to have all of the wiring run to a series of 0.1" pitch connectors on the upper edge of the board, but it is a still absolutely crazy installation. The whole time I have been working on this, for MONTHS, I have been thinking "Is this insane? Will I regret having unleashed this into the world? Will I be having to help people who mess up the installation for the rest of my life? Will I loathe installing them myself when I do commissioned builds?" I fear the answer to all of these questions is YES. I have been dreading making the build/install instructions for it for months.
I was chatting about it with Rob from Retroaktiv and he suggested something that was already scrabbling around in the back of my mind, and hearing someone else say it too made me think I should just do it: making an entirely new panel PCB that replaces the entire original "synth board" (panel PCB) and has all the mods built right in. (continued)