[sdiy] fast-attack EGs and trigger sync

[Richard Wentk]

On 11 Nov 2008, at 05:55, mcb, inc. wrote:

> On Tue, 11 Nov 2008, John Mahoney wrote:
>
>> Yeah, that's basically how Schmidt trigger sharpens a signal.
>>
>> How about using the trigger signal to drive the VCA, in  
>> conjunction with the EG? You could attenuate this attack pulse --  
>> or not!
>
> It's not really about sharpening the signal.  The envelope modulates
> the signal through the VCA and what I'm thinking about is trying to
> lock a phase relationship between envelope and signal.  But would the
> effect be audible and useful?

A Schmidt trigger adds hysteresis - it's nothing to do with zero  
crossings.

Sonically I'm not sure why anyone would want a 0.1ms attack time.  
There aren't many applications where that would be musically useful,  
because your ear can't hear transients which are that fast.

I'm told that a good click elimination trick with some patches is to  
sync the VCOs to the envelope trigger pulse, so that the VCO cycle is  
always locked to the start of the envelope.

You'll probably get more mileage from that than from trying to add a  
zero crossing detector which is fast enough and accurate enough to  
work at 10kHz and which would have to be switched in and out if you  
wanted to envelope a non-pitched or semi-pitched source like a chord.

At low frequencies, waiting for zero crossings is going to add a  
significant delay before the envelope triggers. I can imagine that  
might not be a good thing.

Richard