ARP 2600

ARP 2600 circuit board work
We forgot to take a picture of it when it was done, so here’s a picture of it when it was dirty!

The owner of this ARP 2600 got it in an insane trade in the late 80s… in exchange for a Peavey keyboard amp and a TR-505! A lot of it had never worked in the entire 30 years he had had it.

When we do restoration of an ARP that’s in bad shape, we’ve learned that there’s really only one good way to approach it. We basically strip it down to its bones and do everything we possibly can in one fell swoop before even trying to test different systems. It ends up being so much more efficient that it actually costs less than taking a more step-by-step approach.

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Rebuilding ARP PPCs

Using FSRs (force sensing resistors) to repair PPC "proportional pitch control" pads for an ARP Odyssey Mark III

Because I am now one of those people who thinks they are very busy, I am just going to share a “quick tip” today.

In one of several Odysseys that we rebuilt recently, the “Proportional Pitch Control” pads (otherwise known as PPC, those three spongy white pads that Mark III Odysseys have) were so bad that no amount of cleaning could revive them. I finally was forced to look for another solution, and tried using some FSRs (force sensing resistors) and the results were great.

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Moog Multimoog

Moog Multimoog synthesizer
Moog Multimoog

Should I be embarassed to admit I had never heard of the Multimoog until this one showed up on our doorstep? The Multimoog was a Moog monosynth made between 1978 and 1981 and I’m not sure I understand how it was intended to fit into the Moog product line, or what is “multi” about it.  Continue reading “Moog Multimoog”

Moog Taurus (and a Prodigy)

Moog Taurus I bass pedal synthesizer
Moog Taurus I

The Taurus is a funny little (actually quite awkward and heavy) bass synth produced by Moog between ’75 and ’81 that is designed with a one octave, organ style pedal board meant to be played with your feet. It has a limited number of actual features… just one sawtooth waveform for both of its oscillators, the obvious 24db Moog ladder filter, portamento (glide), and a simple attack and decay envelope for the VCA and filter. It’s basically meant to do one thing well, which is make bass sounds, and it does it as well as any other Moog synth I’ve played. Though, I will admit it is a fun and unique experience to sweep the filter with my foot using a giant foot-sized slider.

Moog Prodigy
Moog Prodigy

We had a Prodigy in the workshop at the same time, which is the Moog Taurus’s immediate Moog monosynth contemporary. Comparing their sounds when set to equivalent settings, even before comparing the schematics it was clear that even at its highest cutoff setting, the Taurus’s filter, compared to that of the Prodigy, was still cutting a good deal of high frequencies. It was really designed to be used as a bass synth only. Continue reading “Moog Taurus (and a Prodigy)”

ARP Odyssey Mark III (and it’s our birthday!)

ARP Odyssey Mark III

I just finished up an inside-out full restoration of this ARP Odyssey (Mark III). I’m replacing the slider caps, which were all missing, with bat style toggle switch caps which I soften with a heat gun until I can slide them over the shaft of the slider, and haven’t gotten the green and blue ones yet, but wanted to take this photo and do a post because today is our birthday! Continue reading “ARP Odyssey Mark III (and it’s our birthday!)”

Moog Model 15 Modular

Moog Model 15 Modular Synthesizer
Moog Model 15 Modular Synthesizer (1974)

My first Moog modular restoration. This beloved American classic is certainly the most terrifyingly valuable synth I’ve ever worked on, worth several times as much as my car, more than the equity we own in our house after paying our mortgage for two years, and more money than I’ll probably earn this entire year. Continue reading “Moog Model 15 Modular”

ARP Axxe (#2) – repair tips for all ARPs

ARP Axxe
ARP Axxe

It’s been almost a year since I began working on the first ARP Axxe I restored, and I was amazed by how much more smoothly this second one went, though it’s not really surprising as I have worked on over 70 synths including a half dozen other ARPs in the year since then. Continue reading “ARP Axxe (#2) – repair tips for all ARPs”

EML ElectroComp 101 – 1 volt per octave conversion mod

This is a really fun synth! EML was a lesser-known American synth company competing with Moog and ARP during the 1970s and made some unique instruments. The EML-101 is a semi-modular duophonic synth similar in structure to the ARP 2600 and very unique and powerful. The bulk of our work on this involved designing and installing a circuit that allows the synth to accept standard 1 volt per octave-scaled CV via its “SEQ” input, as its oscillators have an unusual scale of 1.4 V/octave with a 4.6-volt DC offset. Continue reading “EML ElectroComp 101 – 1 volt per octave conversion mod”

Sequential Circuits Pro One – CPU upgrade and MIDI retrofit

sequential circuits pro one synthesizer
Sequential Circuits Pro One

When we got this Pro One it was acting insane: keyboard playing only one note and/or pitch sliding upwards, loud bursts of noise, weird envelope/triggering behaviors. This synth is unusual for its vintage (early 1980s) in that much of the control voltage for the analog circuitry is generated by a digital CPU, which was hot enough that it burned Darian’s finger when he happened to touch it, badly enough that he still has a blister a week later! So clearly the CPU was bad– and further testing confirmed it. Continue reading “Sequential Circuits Pro One – CPU upgrade and MIDI retrofit”