[sdiy] Korg Lambda envelope

[Florian Anwander]

Hi

I am not too deep in that kind of circuitry, but as far as I understand 
it works like the following (all the gurus: please correct me if I am 
wrong):

Lets take the most upper key in this diagram. As long as the input of 
the gate/divider chip is +V the corresponding note is off. A keypress 
enables a connection via R8 and the transistor (on on the left side of 
the diagram) to -V. This causes a (negative) voltage at R12 and 
following on the Gate-Chip, with the consequence, that the note is on. 
The rise of this voltage is depending on the loading of C11. This 
loading can be slowed down, by a partial current flowing over to the 
attack bus which depends on the setting of the attack pot.
If you release the key again then the capacitor will be unloaded again 
via a current over the release bus which depends on the setting of the 
release pot.

All the best, Florian


David Moylan wrote:

> What I'm talking about is the envelope generation not the VCA section, 
> that's taken care of elsewhere in a chip.  The envelopes (per key) use a 
> global Attack and Release setting.  It's a strange topology with 
> reversed diodes and I can't quite figure out how to decode it.  I think 
> the diode resistance is being modulated
> 
> Have a look.
> 
> Dave
> 
> Paul Perry wrote:
> 
>> This has nothing to do with the present case, but.. it occurs to me 
>> that in
>> the case of audio frequency square waves, you could modulate the 
>> amplitude
>> with a simple diode 'minimum' circuit.
>>
>> Could be useful somewhere sometime.
>>
>> paul perry Melbouurne Australia
>>
>>
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