PAiA 2700 Series Schematics

"The following book contains ALL of the PAiA 2720 series schematics and design explanations except for the 2720-2A improved linearity VCO and the 2720-9 Glide/Retrofit for the
2720-8 keyboard. It also
has the Gnome schematics and all of PAiA's really early kits (Synthespin, Infinity Plus sustain, etc)

Electronic Music Circuit Guidebook by Brice Ward
TAB books #743 ISBN Hardcover 0-8306-5743-6 Paperback 0-8306-4743-0
Library of congress card # 75-20843

David Hillel Wilson
Curator,
New England Synthesizer Museum
DWilSynth@aol.com
_www.synthmuseum.com/nesm_ (http://www.synthmuseum.com/nesm)"

Restoring Patches From Tape

Good tip from David Hillel Wilson, curator of the New England Synthesizer Museum.

"There is an issue with downloading synth patch tapes from the Internet, and it goes like this: The Human ear can't hear absolute phase, so that an up sawtooth sounds exactly like a down sawtooth. However, the cassette input circuits on most synths CAN hear absolute phase. Many of the .WAV files are inverted, either by the sound card the poster used to digitize them, or the sound card you used to play them back. The answer here is crazy, but it works: After trying with no success for several hours to load up an OB-Xa from an Internet wave file, I tried this: I took two alligator clip leads and an extra patch cord, and used them to swap the ground and the hot on the EAR output jack on the cassette tape recorder. It loaded on the first try! You can also run the sound through any inverting mixer (such as on the ElectroComp 200). I have tried to send this info (and the Sequential Split Eight factory sounds as an .SYX) to the website that hosts these files, but my messages keep bouncing back."

Update via swissdoc in the comments: "Why not just inverting it in your soundeditor before saving from the soundcard to tape?"

ARP Pro Soloist Interfacing

The ARP Pro Soloist keyboard has a 6 bit output; 4 bits chose one of 12 pitches, and the remaining 2 bits control the octave. The voice selector card for both the Pro Soloist and the Pro-DGX output a 5 bit code that selects one of the 31 presets, or "Off". Finally, there is an op-amp that buffers a voltage proportional to the output of the aftertouch sensor, and subbing a CV for this output will work even if the resistive strip is dried out and dead. Thus, your MIDI to CV converter should generate a 6 bit code for note-on/off, a 5 bit code for program change, and a CV for aftertouch, and the only thing on the ARP you'll have to touch to play it are the aftertouch destination routings, the vibrato/repeat rate knob, and the portamento on/off switch.

David Hillel Wilson
Curator
New England Synthesizer Museum."

ARP2600 filter 4072 modification?

David Hillel Wilson of the New England Synthesizer Museum has been sending tips and info to the AH list for some time now. These tips usually just come in as an informational email about every month or so. I noticed they are informative and not really meant to engage discussion although of course sometimes they do. They are written more like informational pieces. I asked David if he would be interested in having me put them up on Matrixsynth for others as well. He said yes. The following is the first of hopefully many more on Matrixsynth.

"To see if your ARP 2600 needs the filter mod, turn the frequency and resonance both all the way up. If the sound is still low enough in pitch for you to hear, then you need the mod. If your dog starts barking, you don't need the mod.

In order to modify the filter without unsoldering it, I solder 4 5K6 (Green-Blue-Red) resistors in parallel with the existing 4K7s, and on the foil side of the board. This gives a resistance near the value 2K7, which is what ARP used in the Solus, in which they had fixed the filter themselves, so it's still authentic ARP. Unfortunately, I'm not quite sure how to describe which foil traces to solder to (I've done so many of these I now just do it from memory). Try this: Look for the big chip in the middle (two rows of 7 pins each, spaced 1/10 inch apart, with the two rows 3/10 inch apart). Near the 4 corners of this chip (an LM3900/CA3401E), there are four ovals, each made out of two 3 pin transistors that are glued together. Thus, each oval will have 6 points around the edge. Two of these points (the Emitters) are connected together with a diagonal line that cris-crosses the oval. The only other place each foil trace goes is to a single connection - This is one end of the resistor for that oval. four ovals equals four resistors. The other end of each resistor is tied to a foil trace that encircles the whole circuit, but only makes 4 connections (one at each oval) plus one more in the expo converter. Solder a 5K6 resistor from each pair of emitters to the long outside circular trace, and you're done. (Or if you're near New Hampshire U.S.A. or are willing to send the board, I can do it for you).

David Hillel Wilson
Curator
New England Synthesizer Museum."

Image via this post.

The First ARP 2500

You are looking at the first ARP 2500. It's home is at the New England Synthesizer Museum in Nashua, New Hampshire. I was fortunate enough to actually see it in person a couple of years ago. It was an amazing experience, standing in front of it, realizing what it is. I took a few shots including this one. Title link will take you to them including a much larger version of this one. Also note the SYNTHE license plate on top. : )

What is just as amazing is how Dave Hillel Wilson, the curator of the museum, acquired it. There are amazing deals and then there is this... But don't feel to bad, as you will see, somehow karma has a way of balancing things, but somehow I think Dave still came out ahead. : )

"Many years ago a man tried to sell an ARP 2500 to Daddy's Junky Music in Nashua, New Hampshire. They didn't want it, so they referred him to me. I looked at it and was afraid to offer too little; I offered $500 US. He was expecting to get $50 for it, so he was so happy he threw in his gray meanie 2600 as well. Later Alan R. Pearlman confirmed that this 2500 was the first ever made.

Best purchase I didn't make - I looked at a Buchla Music Easel (before I knew much, but after I thought I new everything) and said it wasn't as good as an ARP Axxe. The guy offered it to me for $400 US dollars and I said no. Boy have I made some stupid mistakes in my lifetime!! (Some guy bought it for 400, turned right around and sold it to a dealer for $1200, who sold it to someone in Europe for $2400, so it's long gone)."

- David Hillel Wilson
Curator
New England Synthesizer Museum
_DWilSynth[]aol.com
_www.synthmuseum.com/nesm

Update: a few more pics below. Note David Hillel Wilson passed away in 2010.

The Moog Cookbook

J-chot is on a mission to spread The Moog Cookbook goodness. He sent me a few good links below. If you haven't heard of them, and you are a synth fan, they are definitely worth checking out. They did a number of covers including modern and classic rock all with classic analogs and a couple of classic digitals including the DKS Synergy and... The Con Brio ADS200! To give perspective on this, according to the New England Synthesizer Museum there were only three Con Brio ADS200s manufactured and only one sold. Think about that... Move over GX1.

According to the last news (2000) posted on Moog Cookbook site (title link), the duo have been keeping busy doing some remixes for others, working with Beck and playing with AIR. Apparently they are in bits of a documentary titled, "Eating Sleeping Waiting Playing" featuring AIR. Pay attention folks, lots of nuggets worth checking out in this post and these sites.

J-chot's favorite shot of them (yep, that is one cool shot).


J-chot:
"can't BELIEVE you guys haven't done a piece on my favorite electronic band the moog cookbook! They were a two piece keyboard group band that did covers of songs in the late 90's with nothing but an array of beautiful vintage synthesizers. They made two AMAZING albums and then disappeared without a trace. Inside the cover booklet of each album was a list of all the synths they used on each song! I SUPER reccomend that you buy these albums. their live shows were supposed to be amazing as each of them were supposedly keyboard wizards. and guess what else? they were big in japan! I'm not surprised at all... It's sad that they disapeared though... they do an AMAZING cover/remix of Air's "Kelly watch the stars" if you can find it.. (oh trust me it's worth the search)

My fav pic of them: http://members.aol.com/mellot/pic2.jpg

Home page: http://hometown.aol.com/mellot/mcb.html

ALbums: http://www.amazon.com/exec/obidos/tg/stores/artist/glance/-/82307/102-5163645-7448110

some of their GEAR: http://hometown.aol.com/mellot/brikeys.html

more gearand band pics: http://hometown.aol.com/mellot/photos.html

here's a little piece by the synth museum: http://www.synthmuseum.com/mc/

here's a music video: http://www.musicvideocodes.com/?artist=6559

there's other little bits and pieces floating around.... but you NEED to educate the world about The Moog Cookbook! [consider it done!] : )


J-chot"

ARP 2600 Bug?

Interesting. David Hillel of the New England Synthesizer Museum (Title Link) just posted a bug with the ARP 2600 on AH. Kind of odd when one crops up after all this time.

From the post:

"I was working on two 2600s with David White when he tried a strange ADSR
setting and
it didn't work. I tried replacing all the transistors, all the diodes, and
the opamp in the ADSR
with no fix. So we tried another 2600, same problem. Tried the 2600 on
display at the
Museum, same problem. They apparently all have it.

How to reproduce it:
Set Attack to maximum, Decay to minimum, Sustain to maximum, and
Release to minimum. If you hit the front panel button, you get a slow
attack, but
if you use a 3604 keyboard, the attack is instantaneous, which is wrong.
Of course,
if the sustain is at maximum you can set the Decay anywhere without
affecting the
result of a properly functioning ADSR, so the workaround is to put the
Decay up
to maximum.

Why it happens:
The trigger pulse from the 3604 is deliberately delayed, which prevents
the decay/sustain
logic from being disabled until a few milliseconds after the gate has
risen. This allows the
sustain setting (in this case, maximum) to back circuit through the Decay
control and
fully charge the capacitor before the slow attack can happen."

New England Synthesizer Museum - Interview

Title link takes you to an interview of Dave Wilson, curator of the New England Synthesizer Museum. I was fortunate enough to visit the museum a couple of years ago. It was a jaw dropping experience seeing so many classics in one location. Dave was a great host. There is also some sample audio of Dave after the hop. And to be clear, I didn't do this interview. I just visited the museum a couple of years ago.

The first ARP 2500 (I took this shot when I was there)

Noise

Ever wonder what makes up the different types of Noise offered on synths? David Hillel Wilson, curator of the New England Synthesizer Museum and host of Synth Museum posted the following on AH. Title link takes you to the Synth Museum website.

"OK Here is the theory. White noise has every possible sine wave all at the
same volume.
Unfortunately, since the Human ear hears frequencies logarithmically, the
pure randomness
of white noise sounds high pitched to us. Since we hear twice as many
frequencies in any
octave as we do in the octave just below it, to create a noise that "sounds"
right requires
that the amplitude of the noise drop off at 1/2x per octave, or 3dB/Oct.
This is the definition
of Pink noise. Further low-pass filtering can make red noise, while high
pass filtering would
make blue noise. There are, to the best of my knowledge, no exact
definitions for colors
of noise other than white and pink. The "Color" idea comes from optics:
Light containing
all colors in equal strengths is seen by the Human eye as "white". If we
remove the higher
frequency (shorter wave length) lights, the color literally shifts to pink,
hence the name."

David Hillel Wilson
Curator
New England Synthesizer Museum