[sdiy] Aaron's take on the Buchla 258 (rough draft)

[Aaron Lanterman]

On Jul 21, 2009, at 2:57 AM, mark verbos wrote:

>> 1) The original 258 has some resistors that you change or leave in  
>> or out depending on if you want a square wave or sawtooth wave.  
>> After studying the schematic a bit, I figured you could switch  
>> between the modes using a three-pole, double-throw switch (which  
>> are available), so I went ahead and set it up to work that way.
>
> be careful. I think the trimming will need to be different for the  
> two modes. If you have your heart set on the switch, you may want to  
> figure out a way to trim the 2 modes individually.

Thanks for the warning! That definitely complicated things... I do  
have my heart set on the switch, so that sent me back to the drawing  
board for a bit.

By using another op amp (basically copying some of the circuitry for  
the two cases), I think I can do it with a 4-pole, double-throw  
switch. I've done a PCB layout in Eagle and am tweaking the silkscreen  
markings now.

- Aaron