[sdiy]on topic Buchla 259 question

[mark verbos]

Aaron Lanterman wrote:

> 
> On Wed, 28 Jun 2006, mark verbos wrote:
> 
>> The Order control fades between the ouput of the wave folding Timbre 
>> section and the output of the saw/square shaper.
>>
>> On the scematics you'll see that on page 3 the square and triangle 
>> signals come in on the left and you see the two outputs on the right. 
>> Page 4 is the order section which is a crossfader between the 2 
>> outputs from page 3.
> 
> 
> Ah - slowly it reveals its secrets.
> 
> Let me see if I can decipher the rest here (or at least part)... the 
> right half of the page 4 implements amplitude modulation with - 
> Vactrols????? Reading that right I am? Vactrols are not very fast, can 
> you really do audio rate AM with vactrols?????

The FM input on a 291 bandpass filter controls vactrols at audio rate. 
It is good up to around 200Hz. However, the range of control will 
determine the top modulation speed. The older version of the Music Easel 
used Vactrols in the oscillator core and I found the FM range to be too 
limited, but I don't ever remember thinking that the AM was restricted 
on a 259. Incidentally, the control circuit around Vactrol G is 
interesting in that it shows how to bend the vactrol response. It seems 
to me that he is making the AM exponential.
> 
> And even with vactrols, the way it's set up looks totally odd.
> 
> I clearly am not doing enough drugs.

not even close. ;)



Mark