[sdiy] MOTM-800 clicks. Arg!

[Fernando de Izuzquiza]

* mailto:fdi at ran.es *


Hi,

I'm very interested on this thread
(and in using both of the EGs described below)

It seems that Aaron Cram worked on that problem (trigger caused clicks)
while designing his very interesting EnvyLope (based on JH's VCHADSR).
Just take a look to his explanation:
http://www.ori.org/~aaronc/synth/EnvyLope_V3.pdf

By the other hand, JBergfors VCHADSR (based also on JH's VCHADSR!)
incorporates an "instant attack" mode (Punch feature) to produce
ultra-fast transients (0.3 microseconds!!!). I still don't know if
there is any VCA out there (if there is tell me, please) that can stand
such a fast transient without clicking -if it can respond so fast-, and
I assume most VCAs will be always slower, so will soften that sharp
transient a bit... or completely?
http://www.idg.se/personal/bergfors/bergfotron/eg.htm

But I also see that is being suggested that the only way that seems to
be possible to get a very sharp attack sound with no click, is
generating it with that dynamic shape inherent to it (ringing filter),
instead via the usual processing procedure (source to VCA, VCA
controlled by transient CV shape)...

So... ???         =:)

Fernando
-- 



f
*




> De: jhaible at debitel.net
> Fecha: 16 Oct 2003 14:58:09 +0200
> Para: Czech Martin <Martin.Czech at micronas.com>
> CC: Aaron Day <aaron at receive-transmit.com>,
synth-diy at dropmix.xs4all.nl
> Asunto: RE: [sdiy] MOTM-800 clicks. Arg!
> 
>> I have heard this fast attack problem on many synths, also digital.
>> I guess all such configurations show the same behaviour, if the
>> envelope is really fast enough.
> 
> Yes. It can be explained directly from signal theory, and would
> even occur in perfectly ideal modules.
> 
> 
>> Another question: we could ask what kind of thing this VCO-VCA-Env
>> thing is modelling. If you create sound by applying a impulse to 
>> a 2nd order resonator, you will see that the rise time depends
>> on frequency and resonance. Perhaps a very simple ideophon
>> model. It will never happen that the wave starts at 100%, the
>> differential equation will always start with 0 (given the initial
>> conditions say so). I've just done this for a composition
>> I'm going to present this Saturday or Sunday.
>> 
>> The usual synth circuits divide the action
>> of a resonator in two parts, frequency and time transient,
>> which are not correlated. Thus it is not surprising that things
>> do not work as supposed (in the sense of said modelling).
> 
> That's a very interesting way too see it - I never thought about
that,
> but it makes perfect sense. Maybe that's also the reason why synth
> that only have a single envelope generator (shared by VCA and VCF)
> often produce a more "natural" behaviour. Of course that's a big 
> limiation as well - every time I played with a 1-ADSR synth, I wished

> I had a second ADSR. But often, when I _have_ 2 ADSRs, I wish the
> 2nd would "follow" the first one somehow. Would be easy to implement
> with two VCADSRs: One set of knobs for common A. D, S, R values,
> second set of knobs for (relative) offset A, D, S, R values on the
> second EG.
> 
> 
> Linked parameters can often be very nice. I've been playing with
> VC ADSR parameters on the PolyKorg Clone a lot recently. I think
> with full polyphony available, the behaviour of release becomes
> even more important. (No need to model everything exactly, when
> the release is cut off 8 notes later, anyway.)
> I found that the usual prolonging of the Release time for
> a "damper pedal" effect can be much improoved if the Decay
> time is adjusted accordingly as well. But I disgress.
> 
> 
> Back to the Attack click problem. Many non-modular synths have
> a small time constant (RC-filter) built-into the VCA, in order
> to limit the transient speed of the EG. With a nonlinear VCA
> CV input, this would even be different from ordinary 
> filtering, and different from ordinary slew limiting as well.
> Just think of the famous Vactrol-based VCAs!
> On a modular, you want more degrees of freedom, and you want
> to _allow_ sound that sound unnatural. This can mean your
> emvelopes can be faster than you really want them for a certain
> application. Referring to Martin's example of a 2nd order resonator,
> no think of a "real" bass drum, for instance. If you hit the base
drum,
> the hitting may produce a transien that is faster than the damped
> oscillation after the impact, but _how_much_ faster can it possibly
> be? (on a real bass drum?). Will certainly depend on the strength
> of the impact, damping from the beater's material, and so on.
> But will it be as fast as the 1 ...2ms of a "good" synth ADSR?
> 1ms coresponds to a quarter-cycle (i.e. zero-to-maximum) of a 250Hz
> resonator. But this zero-to-maximum excitation will only happen
> when you really synth your VCO to the ADSR such that it starts with
> a zero-crossing. Think of it: If your ADSR strikes at the VCO
> wave _maximum_, whis coresponds to a drum membrane that is sort-of
> "plugged". If you have a 1ms transient, it's like plugging a
> membrane that's tuned to 250Hz (approximately).
> 
> 
> JH.


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