[sdiy] Wave Multiplier-like circuits?

[Aaron Lanterman]

On Oct 26, 2009, at 11:55 PM, Adam Schabtach wrote:

> I also know that there's at least one old Buchla module that does  
> something
> like this but I haven't yet chased down info, schematics, etc.

The Buchla ones are really clever - they deliberately "voltage starve"  
the supply so that the op amp output can't generate the voltage needed  
to keep the inputs at the same voltage in negative feedback mode,  
forming a kind of "deadband" circuit without diodes. I have never seen  
anything else like it. I've always wondered how Buchla came up with it.

I've heard a rumor that the nonlinearity in the new 261e is made using  
the same starved-op-amp trick as the 259 and the Easel, but I have no  
idea how actually true that it. It does sound the same to me.

It's also very similar to the Serge wave multiplier although that's  
done using a rather different technique (and equally clever).

- Aaron