Category: ARP

In this video, I explain how polyphony is achieved on the ARP Omni 1, Omni 2, and Quadra synthesizers using a master oscillator, top octave divider and frequency dividers. I discuss how this type of polyphony is different from the type of polyphony on the type of synthesizers with fixed number of voices, like the Prophet 5, Oberheim OB-X, and Memorymoog.

I also introduce 3 of my new retrofits–a drop in replacement for the Master Oscillator, a replacement for the TDA0470/TDA0470D gating IC chips, and a replacement 4075 voltage controlled filter.

00:00 Polyphony discussion
03:40 Master Oscillator replacement
09:10 TDA0470SC
10:06 4075 VCF Replacement

The pushbutton switches on the ARP Omni 1 synthesizer suck. The mechanical latch often breaks, leaving us unable to turn on sections of the synth. Other times, we need to press the switch at just the right angle to be able to get it to latch. And yet other times, the switch contacts get dirty and the switch gets stuck off or stuck on.

The originals have been obsolete for decades and are unobtainable. So I’ve created a drop-in replacement switch, that fits the old switch cap! Check it out!

ARP Omni 1 Replacement Switch

Functional demonstration of the ARP Axxe 37 key monophonic analog synthesizer keyboard. Also discussion of what went into restoring it.

ARP Axxe Analog Synthesizer Keyboard Fully Serviced w/ LED Sliders & new Walnut Panels

It’s time to dig into my stash of ARP Quadras and get a couple of them overhauled and back out into the world. This Quadra was looking really sad, all of its slider shafts were sheared off, and it was shipped to me partially disassembled and in disarray. But the seller said it was working… NOT!

In this video I share (just some of) the ordeal it took to get this Quadra awesome again. Including refurbishing sliders, replacing broken slider shafts, repairing battery corrosion, replacing a dead CPU chip, dead oscillator, dead bass section, no output, broken phase shifter, and the list goes on.

This ARP Quadra is now for sale below.

Restored Vintage ARP Quadra Synthesizer Keyboard

I bought several broken ARP Odysseys, and as is common with the Black & Gold ARPs, a number of them had heavy wear to the gold lettering on the panel. After meticulously restoring the electronics of this one, I decided to risk it all to see if I could successfully re-silkscreen the panel graphics myself. The result wasn’t impressive. Though it made usable again a synth that was otherwise unusable since you didn’t know what slider did what.

Vintage ARP Odyssey Mk II 2813 w/Moog Ladder Filter Fully Serviced w/ LED Sliders

I have 2 recently refurbished ARP Odysseys side by side. They’re identical model 2800’s except one has the original 4023 voltage controlled filter and the other has my clone of the 4023. Which one do you think is the original??

While restoring this ARP Axxe I found that the voltage controlled filter wasn’t working right–it wasn’t filtering anything! In this video we put the filter into my ARP Filter test fixture and track down the problem using the schematics.

In the last part of this series, we repaired the power supply & recapped this lovely Rhodes Chroma. Today I show you some of the upgrades I made to the Rhodes Chroma, and we have a listen to some of the many sounds the Chroma is capable of.

My usual disclaimer: none of the sample sounds played are intended to be musical, I am not demonstrating my musical ability (or total lack thereof), just showing some of the sounds the Chroma can make.

In the last video we figured out why this Rhodes Chroma wouldn’t work. In this video, we make the repair to the power supply as well as recap the synth and clean up some corrosion on the CPU board.

Viewer submissions for new time-lapse soldering music is welcome!

Before this Omni gets shipped off to the UK, I explain the mains wiring and show how to convert an ARP from 120V to 240V operation.

You will learn why the lamp on the power switch is meaningless as a diagnostic indicator, as well as where there is a dangerous wire that is color coded neutral but is actually hot mains level.