[sdiy] HELP! How can this possibly work? Buchla Music Easel env generator?

[Dave Leith]

ah...thank you!

dave

PS (should have re-read your blog)

On Wed, Jan 12, 2011 at 11:48 AM, mark verbos <mverbos at earthlink.net> wrote:
>
> On Jan 12, 2011, at 2:05 PM, Dave Leith wrote:
>
>> The circuit diagram is on Magnus's site here
>> http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2080_3_200.jpg
>>
>> The question is about the pulse input <6>. If the puse comes thru
>> a120K resistor to point <6> then the circuit is supposed to sustain as
>> long as the pulse is high. Once the pulse goes to 0 volts then the
>> decay begins.
>>
>> In the other mode (transient) the pulse goes thru a 390K resistor to
>> point <6> then the envelope generator is supposed to be in transient
>> mode where the envelope is triggered and should go thru it's cycle
>> independent of the pulse going low.
>>
>> IC4 where the pulse is conditioned appears to be a comparator that has
>> 2 states hi or low. This is the part that is the mystery to me. How
>> are the two envelope generator states created from this.
>>
>> Envelope generator operation is also explained here.
>> (http://rubidium.dyndns.org/~magnus/synths/companies/buchla/PaMtEO_16.gif)
>>
>> Front panel wiring to the envelope generator is here.
>> (http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2080_13B_200.jpg)
>>
>> Thanks for any help that can be offered
>>
>> Dave
>
> Dave,
>
> Buchla pulses are made up of a short, tall spike followed by a sustained, lower gate. In the early days, they were 15 volts and 7.5 volts, later they were switched to 10 volts and 5 volts. If you are cloning this circuit and expect to get the two modes from a normal gate, you will have to send the gate through a cap to get transient mode.
>
> Mark
>
>