Buchla 281 - quad function generator - Not your usual ADSR

These are some basic notes for the Buchla 281 module that I'm putting together for a friend.

It's probably one of the most common (and essential) of Buchla modules.

Don called the 281 a function generator, rather than a plain old envelope generator.

I think this is warranted as it's not your standard ADSR. 

Depending on how it is patched, you can produce really complex wave forms.

 

In  most electronic labs you will usually find a function generator. 

This was a rather large, intimidating and complicated looking piece of electronic test equipment. It might even be software.

The FG was developed to produce various types of wave forms for testing electronic circuits.

 

 

 

The Buchla 281

The 281 is made up of 4 function generators

 

They are named A, B, C, D. (Top to Bottom)

They are independent, but the module also allows you various ways to combine their outputed voltages.

 

You can patch  within the module.

Inputs are on the left. Outputs on the right.

The top left orange jack is a pulse input.

The top right red jack is a pulse output.

The bottom left black jacks are CV inputs to control  attack & decay. 

The bottom left is your CV output.

The toggle switch allows selection of 3 modes of operation.

 

1. Cycle. 

This similar to an LFO. It's my favorite clock source. I will often use this as my master clock.

 2. Transient (Attack-Release)

3. Gate ( Attack-Sustain-Release)

 

 

 

The bottom section combines -- A& B & C & D --- Quadrature & ORs.

 

The OR is what's called "Analog Logic" or Fuzzy Logic," it simply outputs the highest voltage of the two envelopes. It uses diodes.

 

It's a combiner , not a mixer.

 

 

"OR" has nothing to to with binary logic.

 

If you look at the top knob, its current setting  is all CVs from Function Generator A. 

As you turn it clockwise it blends in CVs from FG B

 

http://buchlatech.blogspot.com/2008/10/adsr-and-buchla.html 

Quadrature Mode

When this is selected, two generators are linked together in a loop configuration so that FG "B" will be slaved to "A".and FG "D" is slaved to "C".

 

""if the TRIG A switch is in the up position, envelope generator B will be triggered,
regardless of the position of the trigger select switch when envelope generator "A" reaches
 the peak of its cycle. (The end of its attack segment.)

the Trig B switch creates the same situation between envelope generators C and D.

 

( 1981 Buchla Synthesizer User Guide.)

 

Modular Synthesis has a very good explanation 

https://modularsynthesis.com/roman/buchla281/281_qfg.htm

 

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