[sdiy] [AH] Buchla 192 design [was: Buchla used for Silver Apples of the Moon]

[Aaron Lanterman]

On Jun 26, 2010, at 6:02 PM, cheater cheater wrote:

> Have you tried that with NOS parts that were used in the actual
> filter? Maybe the manufacture methods have changed something subtle
> that gives a big difference here?

Nope; in general I steer students away from insisting on using original parts if they are difficult to come by, and using some readily available modern substitute.

In general, I think the original design in the patent is just a mess, and also the design finally used in the Hammond is still a mess, just slightly less of a mess. The TL082 or whatever Kaylah (the student who worked on this) originally tried had to be replaced with a 741 to avoid oscillations. Also, two resistors on the Hammond schematic have "factory selected" resistors in parallel with them, which shows how teetering-on-the-edge the design is. 

When Kaylah tested her in-solder version, she had to change those resistors from what they were on the breadboard to keep the circuit working.

> You'll have to give me some tutorials or something ;) But really, I need to sit down and read some books.


I might suggest a textbook by a couple of my colleagues:

http://www.amazon.com/Circuit-Analysis-Approach-Russell-Mersereau/dp/0130932248

Any circuits book will talk about Laplace transforms, but this one particularly emphasis it and a "signal processing" viewpoint. It was intended to become the circuits textbook used at Georgia Tech, but too many faculty (particularly the "what happened to my three-phase power?" crowd) shot it down.

The book has some flaws (I hate the "1 ohm resistor" with "1 farad capacitor" problems), but it does try to take a different-than-usual viewpoint.

Dang, it's expensive; I'd recommend finding a cheaper used copy.

- Aaron