ARP 2600 #26907:  THE PROBLEM CHILD

The ARP 2600 is a wonderful synthesizer, and these have been around since the early 1970s.  It has three oscillators, a Moog-like filter (earlier models) or ARP-designed filter (later models), two envelope generators (one ADSR, one AR), an envelope follower, lag processor, inverter, noise generator, sample and hold...and even speakers and built-in reverb.  It is built into a case and is "luggable".

Originally the ARP 2600s were designed as synthesis teaching tools.  The ARP 2600 will play without patch cords.  This is because it has "normalized" connections, meaning that enough of its modules are pieced together to make sound without requiring any external connections.  This is similar in concept to the Minimoog.  However the real fun starts for the 2600 when you add patch cords.  Patching breaks these normalized connections, so you wind up creating the separate components of a modular synthesizer.  The Minimoog has limited patching capabilities, mostly limited to one oscillator or the noise source controlling pitch and filter.  With the ARP you can do much more.

With its original keyboard the ARP 2600 is monophonic, meaning only one note plays even if you press more than one on the keyboard.  The 3620 keyboard allows you to play two keys at the same time and hear two different notes.  You do this by patching the output of the second note to one of the oscillators in the synth.  The 3620 also adds a low frequency oscillator, which you can use to add vibrato to a sound...or patch it into anything you want.

  Oscillator 1 and preamp/envelope follower section

The ARP 2600's Moog-like filter

  Amplifier and envelope generator sections (click picture to enlarge)

Note the black (or copper clad) modules in these synthesizers.  These are "encapsulated" in epoxy, done that way so someone could not steal and copy the designs.  Well, that's fine, except for one thing:  It makes the modules nearly unrepairable!  So if you are purchasing a 2600, you need to be aware of this.  Fortunately there are some replacements available.  Read on.

The ARP Arrival

This EBay deal arrived in the summer of '04 and began living up to its eventual nickname immediately:  The Problem Child.  The machine was a basket case and a fire trap.

An attempt at balanced inputs/outputs?

I could get some sound out of it, so I knew the oscillators and filter were working.  At least it wasn't a total loss.  I spent a little bit of time with the machine and the schematics, but this one was going to be over my head.  Instead of stopping there and sending the machine back to the seller (which was an option), I made a deal with the seller to refund part of the purchase price and opted to bring it to Phil Cirocco, who not only fixes ARP synthesizers (and all kinds of other synths) but has also created a series of upgrades for the ARPs.

In addition to repairs to the synth and keyboard, some of the upgrades installed into this 2600 by Phil include:

I brought the machine to Phil in mid December 2004, and I told him not to rush and to work on it as he had time, as I'd be picking the instrument up personally and wasn't in the area a lot (it's a 400 mile drive).  As luck would have it, my cohort on "Improvised Waves" Jimmy Moore was coming from Phil's area for the Unveiling of Mellotron FX Console #10006 earlier in 2005, and he picked up the repaired ARP from Phil.  Phil told Jimmy that this particular machine was one of the toughest---a "problem child"---but Phil prevailed.

In Vermont the ARP was working well for the most part, but, staying true to its nickname, there were still one or two things to be worked out.  There was an annoying "pop" when the 3620 keyboard was used, and some more of the old 1/8" jacks had failed.  So while heading home from our Mellotron adventure with Martin, Medeski, & Wood in May 2005, I brought the synthesizer back to Phil.

Phil went over the synth again, and he found the culprit of the pop:  A blob of solder was shorting the CV and trigger pins on the keyboard!  This was a problem from the factory!!  Phil updated a bit of the keyboard's components while he was in there and replaced a few of the 1/8" jacks.  The synth was finally done!

I picked up the synth on my trip to New Jersey for the unveiling of restored Mellotron M400 #310 in early August 2005.  Phil mentioned that, yeah, it was about one of the toughest ARPs he'd worked on, but it's also one of the best sounding, too, and it came out nice.  I agree.  Phil took a sow's ear and turned it into some nice, drippy fat.

And if you thought "The Problem Child" was tough, check this out:  Phil is restoring a Hammond Novachord!

While at our get-together in New Jersey we all had fun with the ARP.  Dave Schwartz was trying to pick out the lines from "Hero and Heroine" on the Mellotron and Prophet 5, and I was just noodling, probably throwing him off.

As a special treat, Larry and Phyllis Fast also took the opportunity to play a few notes on the ARP.

On that Sunday morning I was up early and started horsing around with the ARP and the Mellotron.  I wandered upstairs from the basement to see if Dave was around, but Mr. I'm-Up-Early was still snoozing.  Eventually he found me, and I told him that the Mellotron was "sounding funny" and he had to come check it out.

I told Dave to hold a chord down on the 'tron...and there was no sound.  The I told him to hold the chord longer, and the sound faded in.  !!??  The attack of the 3 Violins on a Mellotron is very fast, so what was this "fade in" stuff?  It took Dave about a second to figure out that I'd run the output of the Mellotron into the ARP.  The ARP's envelope follower listened for the Mellotron's sound and then triggered the ARP's envelopes, which were set to open slowly, hence a "fade in".

It's also possible to use the synthesizer's filter to change the Mellotron's sound (or sound from any external source).  I've done this before with the PolySix sending its sound through the Minimoog's filter, and it makes the PolySix sound like a completely different animal!

We messed with the Mellotron playing through the ARP for a few minutes more, and then Dave said, "Hey, can I do that with my Strat?"  No problem, and we soon had a wah-wah kind of effect on the Stratocaster.  A little more twiddling, and we figured out how Pink Floyd could have done the guitar/bass part from "One of These Days" off "Meddle".

Very cool.

Thank you Mr. Cirocco for your efforts and patience with the machine.