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

Update, 8/2019: we are now selling PCBS and kitsf that make it easy to install this mod! Click here for details.

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”

Oberheim OB-8

Oberheim OB-8
Oberheim OB-8

This synth is a beast! It’s almost as deep as my work table. When it arrived at the workshop it was really freaking out.  It would overheat after 10-15 minutes and the CPU would crash, freezing the panel LEDs and making no sound. It was missing maybe half of its notes and apparently one of its voices. Continue reading “Oberheim OB-8”