ADSR and the Buchla

The Buchla is not usually associated with keyboard type ADSR envelopes.

I patched up a 281, plugged into the 107 voltage controlled mixer to make some percussion sounds. The good thing about a 100 series gate like this or the 110 is that they are all transistor and don't have the characteristic Vactrol mushy attack. Everything has it's place after all.

I have a loop going, so the envelope keeps triggering, while I work on it. I started with function generator 1 in looping mode and it's trigger out plugged into the trigger in on function generator 2. In this patch, both are triggering at the same time, and I'm taking the voltage out of the combiner section at the bottom. It is a diode combiner and not a mixer, so it puts out whichever is the higher of the 2 voltages at any given time. If the second function generator is set with a slow attack, you can create a cool, compressed drum type sound, where there's an attack followed by a swell in the decay portion. If you put the switch into AR mode on function generator 2 you can play this from a keyboard with sustain.


Then I put the 281 into quadrature mode. The pulse output from function generator 2 plugged back to the pulse input of function generator 1. This gives you a AHDSR of sorts. The Attack control of function generator 1 controls the attack time. The attack control of function generator 2 controls the peak hold time. The decay control in function generator 1 and the pot in the combiner section control the decay and sustain (unfortunately decay is the time of decay AND sustain so you have to massage them to get what you want). The decay control on function generator 2 controls the release. This setup is good for making hard punching sounds, because of the peak hold. Again, put the switch into AR mode on function generator 2 for sustain.



The final option I can come up with right now, is to invert the second function generator. The first function generator's pulse input is where the envelope is trigger from. The quad mode is on. The cv out of function generator one is plugged into a voltage processor and turned up to 100%. The CV out of function generator 2 is sent into the voltage processor and inverted, it's inverted gain will then be the sustain control. It should be in AR mode. The attack control on function generator 1 is the attack, the attack control on function generator 2 is the decay. The decay control on function generator 1 is the release and the decay control on function generator 2 should be all the way down (it's sort of a delay until the next envelope fires if this is all looped). What I like about this is how it always completes the full attack and decay faze before it starts the release, unlike a "normal" ADSR. That makes it great for sending a pulse from a sequencer and getting percussion envelopes with full control.

Oh, and you can tweak the shape of the segments with feedback too...

This ol' 281

There are two versions of the 281 Quad Function Generator. I have one of each in my system. The older version has blue PCBs and circuitry for remote control. The newer, yellow PCBs and the "remote" switch does nothing more than turn on the LED. I received this older one as part of a trade, in dysfunctional condition. Just one of the 4 envelopes was working. The panel is beat up, some of the silk screen has come off, presumably from stickers being stuck to it for 30 years. The knobs were discolored and the arrows had worn off. One switch was broken and one was missing.



I replaced the switches and all the knobs. Then, I attacked the circuitry. After some song and dance, I found that the CA3080s on all three and the LF356s on two were not working. The odd part is that 4 out of 5 of these were already in sockets (not all the chips were) and all 5 were metal cans. It seems so much less cool to put in plastic DIP chips, but whatever works. Aren't these bad boys supposed to be MORE robust?

This design has resistor values on the schematic for 15volt systems or 10volt systems. i came to find out that mine is set up for 10volt systems, which makes it match my yellow board version. Anyway, it's nice to have it working.

My first 280

Today I worked on my first 280 Quad Envelope Generator. I was told that the top envelope seemed to get confused when it got pulses from certain modules. Once it got into this confused state, it was inconsolable. I didn't understand this condition at all. 2 of the 4 lamps are burned out as well.

There are 2 versions of the 280 module. I'm not sure what the deal is, since they were designed only 3 months apart, on March 23rd and June 21st of 1971. I guess this means the first one was a dud of some kind, and I don't know how many, if any are out there. This one was of the second type. (I'm guessing there was a third design as well, since the pictures I got from www.electricmusicbox.com show one with no lamps or pulse outputs and both schematics I have show these.)


Anyway, the problem turned out to be that someone had replaced the input comparator opamp with an LM307 instead of a uA741! I never would have guessed that this would be a problem, but when I opened it and saw that only the weird channel had a different opamp, obviously I was suspicious.

The lamps are still dead. Since they are enclosed in a lens apparatus that is panel mounted, they are not an easy replacement job. I have been told that cutting the back off and sticking another lamp inside the lens is the only way to keep the look. The owner and I have decided to replace all 4 with LEDs inside the lens, since the lamps are so slow they don't even light on short envelopes. Plus, I really don't want to replace them again.

Oddly, the 292 on the bench today had a bad uA741 as well. They must suck. ;)

Overall, I have developed a fondness for this module. On the surface, it would seem that a 281 is better than a 280 or 284, and capable of all of their tricks plus more. But, this little guy does his job with a swagger that can't be duplicated. Oh, and the output swings a FULL 0-15 volts.