How Sound Selection works in the Yamaha CS-80

Yamaha CS-80 angled closeup of front

One of the things that has been the most helpful for me over the years in sort of syncing up my general understanding of electronics theory with understanding how synthesizers are actually designed is reading circuit descriptions in service manuals. A lot of the American companies especially wrote really great, detailed explanations of how their instruments worked, and reading them has helped me to both understand the specific circuits they discussed, and understand more broadly how different objectives in synth design can be achieved… and more quickly recognize what’s going on in an unfamiliar circuit.

Because I’m a nerd I guess, I thought it might be fun to make some step-by-step “circuit descriptions” like that for synth circuits that don’t have them.   My first featured circuit –the system through which the Yamaha CS-80 handles preset, panel and memory switching– is sprawling, but actually fairly simple, much like the synth that it comes from. Continue reading “How Sound Selection works in the Yamaha CS-80”

Restoring the Saddest Minimoog in the World

trashed Minimoog Model D

When this Minimoog Model D arrived a couple of years ago, it was probably the absolute most thoroughly wrecked synth I had ever agreed to work on. I made a deal to do it for a flat fee, even though I knew it wouldn’t be technically “profitable,” under the condition that I could take my time on it, kind of as an absurd challenge to myself and because I knew it would be really satisfying when I finally finished it. Since it is finally done and restoring it was such an insane gauntlet of tasks, I thought it might be worth reviving the long-neglected Shop Blog with a post about it! Continue reading “Restoring the Saddest Minimoog in the World”

“Don’t be that guy”

Roland CSQ-600: in which the tech replaced the NiCad memory battery but installed the replacement battery in a ziploc bag ziptied to the mains wiring.

One interesting thing about restoring vintage synths is that almost every instrument that we work on has been worked on by another tech at least once before. And it seems that more often than not, those other techs were… not great. We see a lot of bad work, but my favorite examples also feature a very special element of absurdity. Here are some recent highlights:

Continue reading ““Don’t be that guy””

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.

Continue reading “ARP 2600”

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.

Continue reading “Rebuilding ARP PPCs”

Moog Sonic Six

Moog Sonic Six
Moog Sonic Six

The Moog Sonic Six came out the same year as the Minimoog Model D and was actually developed as the Sonic V by a company called Musonics which  purchased the financially struggling R. A. Moog Company in 1970. After the merger, the Moog team did some tweaks on the synth and released it as the Sonic VI or Sonic Six.  Continue reading “Moog Sonic Six”

Crumar T1 “Organizer”

Crumar’s T1 is a surprisingly nice 70’s drawbar organ that used the latest octave divider chips that were present in a lot of keyboards of that era. An additional feature that makes it more useful than your average organ is the addition of a very rich, fuzzy bass synth voice that can be added to the lower octaves of the keyboard. The synth voice has a basic resonant filter and a decay envelope that you have some control over. The organ voices sort of drop out in the bass section, so it really helps add a thick low end that would otherwise be lost. It also has a really nice LFO that can be applied as both a tremolo and a vibrato and the speed is controlled with a rotary pot.

Continue reading “Crumar T1 “Organizer””

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)”

Crumar RoadRacer

the Crumar Roadracer electronic piano
the Crumar Roadracer electronic piano

Another idiosyncratic instrument from the Italian company Crumar, who brought us such underappreciated un-classics as the Multiman S and a T1 organ that Darian’s working on right now. This is an example of a type of “electronic piano” that was briefly popular in the 1970s, when top octave generators and multi-stage frequency divider ICs allowed the architecture that had been used in the previous decade’s combo organs to be made much more small and compact.  Continue reading “Crumar RoadRacer”