ARP Avatar – Retroaktiv patch bay kit installation and the vintage synth modding controversy

ARP Avatar with Retroaktiv “Modular Patch Bay Kit”

This was a pretty big mod project that Darian finished a few weeks ago on an ARP Avatar, the ARP guitar synth which is mostly just a keyboardless Odyssey with a bunch of guitar-processing junk that no one cares about. That’s just a fact. Anyway, several years ago New England Analog developed this kit to break out a lot of the CV input points and modulation sources of the synth’s architecture to 1/8″ jacks mounted on a single long PCB, and now that New England Analog has closed, a new version of the kit is available from Retroaktiv.

After giving the Avatar a thorough servicing according to the procedure we follow for all ARPs, the first step to installing the kit was to drill the holes for the patch panel. The panel of the Avatar is fairly thick steel for a synth panel, and we did this drilling task with a drill press. It’s hard to imagine doing it without one, and it was also much faster as a 2-person job.

Drilling the holes for the Retroaktiv patch panel

The next step is to solder the jacks into the patch kit PCB and secure them into the panel with their nuts. From this point on everything is done with the panel in place.

The process of installing the kit requires no fewer than 100 wires, teased out of two 50-wire ribbon cables that come with the patch bay kit, to be soldered to various parts of the Avatar board. Many of these require traces of the PCB to be cut.

The instructions that come with the kit say to estimate 8-10 hours for the time it takes to perform this upgrade. We scoffed at this estimate, thinking it would not take that long, but it definitely did take that long.

Final "gut shot" of Retroaktiv patch kit installed in ARP Avatar
Final “gut shot” of Retroaktiv patch kit installed in ARP Avatar

It is impossible to make the end result not look a little insane. We always strive to have all our work, even mods, looking neat, but there is only so much that can be done with 100 wires having to be soldered all over the back of the main boards. One unfortunate effect of this mod is that it makes the synth a lot more difficult to take apart to service in the future.

NOTE: there is a mistake in the Retroaktiv instructions. The points where it says wires B18 and B19 should be soldered, must be reversed.

This is a powerful and fun mod though, that is about as well-designed as it could be and turns the Avatar into a baby 2600.

Some thoughts on the surprisingly controversial topic of vintage synth mods

I’m about to start on another one of these kits, as well as also being in the process of doing a couple of other mod projects, and have lately been surprised that there is a lot of controversy among synth techs about whether modding vintage synths is appropriate or OK, especially with regards to mods that involve non-reversible physical changes such as drilling holes in them. In a discussion in a Facebook synth tech group Darian and I are both members of, some people were going so far as to suggest there was something unethical about performing non-reversible mods to classic vintage synths, like it amounted to destroying important historical artifacts. Here’s what I said in that discussion.

“I won’t refuse to do a mod for the sake of preserving a synth as some kind of historical relic if it’s what the client wants and it is ‘electronically responsible’ (won’t cause circuit damage over time). However, I will certainly caution them that it could potentially decrease the resale value of the synth and do it as cleanly as I can.

I don’t really subscribe to the idea that even very rare vintage synths should be treated as antiques, historical specimens or museum pieces. I do treat them with respect and care and do careful restorations, but in my eyes, they are first and foremost musical instruments, tools for making music, and I’m happy to help a musician turn the synth they have into its best version of the synth they want, that is most useful to them for that purpose.”

To expand on this further, I think we should also remember that these instruments were designed by people who were engineers, not conceptual artists, who would have wanted their instruments to be the best versions of themselves as well. I’ve read posts from collectors talking about replacing capacitors with NOS ones to make the inside of the synths look “original” even at the expense of their electrical performance. Certain people have been affronted to hear that I once dared to modify the keyboard circuit in a Moog modular to make it more stable, but I feel like the Moog engineers would not have objected to this course of action; in fact, the engineers of all of the great American synth companies used to routinely release updates and improvements to their designs and encourage technicians to perform them on any units that came into their shops.  I’m a pragmatic person, and I guess I have a pragmatic relationship with synths… they are musical instruments designed by engineers and as a musician and a technician, it is my objective to make them work as well as they can work, both as musical instruments and as machines.

So if you tell me you want to mod your synth in some crazy way to make it into the synth you’ve always dreamed of, I will work with you to make it happen. But if you tell me you want me to source 40-year-old power supply capacitors so it can look like it did inside 40 years ago at the expense of its electrical health, I will most likely refuse.

5 thoughts on “ARP Avatar – Retroaktiv patch bay kit installation and the vintage synth modding controversy”

  1. Thanks for this, good read. I think like most controversies it’s not all back and white, it really depends on the case. I would probably not do extensive mods on my own gear cause I appreciate the original limitations (to a point) and the way that shapes the sounds you come up with. Sometimes the mods would give a small push the the original machine needed and wasn’t possible at the time for processor limitations etc. (organix for JX-3P or IO for JP-4 are indispensable) and other times it completely changes the philosophy of the synth and turns it into a different machine altogether (Kiwi 106 is basically unusable without a reference sheet, practically the opposite of the philosophy behind Junos). I like what Tubbutec are doing in this space for example, just adding the right amount of features respecting the original machine, improving things in the right places and never overloading the user interface. Modding is fine but striking a balance is also important.

  2. Totally agreed, I think any mod to help a synth interface better with other gear (MIDI retrofits and upgrades, CV scaling mods, etc) is great, and sometimes even essential… I personally think every synth should have MIDI if possible! There are also a lot of people making free and open-source firmware upgrades for vintage synths now (Bob Grieb at has made an amazing number of excellent ones seemingly just for fun in his spare time) and I think those are some of the best types of mods. But I also agree that those sorts of “digital infrastructure mods” can go too far for my personal tastes, and some of the Kiwi mods do fall into that category. I won’t say they’re not good or tell someone not to have me do them, they just don’t jibe with my personal preferences regarding how I want to experience those synths.

  3. Has anybody considered a similar mod on the KArp Odyssey Module?
    Appreciate SMT components are used but I’m guessing it’s a possibility?

    1. I think that it would be way too time-consuming and risky to the SMT board to be reasonable. Soldering 100 wires to an SMT board would be an insane proposition!

  4. In this case, it is an Arp Avatar, which was designed for use with a guitar…and it failed at that (and this one doesn’t work with the guitar interface and the module associated with the pitch to CV conversion is lovingly coated in a solid square of obaque epoxy resin. I feel zero qualms about having it modified into something…well….Useful 😉

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