[NM] DIY envelopes, 303 cloning

[Rodge]

haven't had a chance to check this out but, but from what you write  
it sounds like you've been listening carefully...


On 05/03/2006, at 12:33 AM, Sven Roehrig wrote:

> Again i try to patch the perfect 303 and like every year i got new  
> information whats really happening inside the machine.
> This time i was listening to the filter before it reaches the vca  
> on a devilfish 303...one where you can switch off the so called  
> accent sweep circuit...
>
> since 2 days i tried to patch it...and ..havent succeded..but  
> eneded with all sorts of really nice filter modulations... its  
> defenetly worthy to do filter modulation with DIY or modified/ 
> biased envelopes. gives a much more alive and analog sounding  
> result than the standard configuartions..
> So any expert patchers out there might like to give it a try aswell.
>
> Problem
>
> In the 303 we have accented and un accented notes...
> a cutoff and an env amount knob...
>
> with cutoff full up.. the accented notes have a distinctiv impact  
> on the filter..rising its frequencie..falling down to the initial  
> setting with around 200 ms... closing the cuttof also lowers the  
> max freq of the accent peak...
> there is a fixed distance between cutoff point and accent cutoff freq.
>
> so far so easy..but...whats happening when you turn up the env  
> amount...
>
> first: it lowers the cutoff freqencie...turning up the envamnt knob  
> turns down the cutoff freq significantly..while rising the the  
> amount of env modulation from a small bip..to the buzzy max cutoff  
> freq we have on the accented notes... on max env amnt accented and  
> unaccented notes are the same filterwise... (given the same decay  
> time for normal and accented notes)
>
> And now ...the part that makes it really difficult...
>
> on accented notes opening the env amnt dont changes the maximum  
> peak...the buzz stays the same..but the frequencie the filter is  
> falling to gets lowered... and this by keeping the falling time...  
> means tones get longer by getting deeper at the end ! That is the  
> factor what makes this knob so dynamic on the 303...
> in maximum setting the filter sweep appears to be twice as long by  
> keeping the maximum...
>
> Not like a normal env amnt on thhe nord that makes the peak higher  
> but keeping the time of the sweep the same.
>
> biasing the cv to keep the maximum is easy but you still have the  
> same sweeptime..resulting in the impression that the sweeps  
> actually get faster while opening the env amnt...
> A mistake all 303 emulations on the nord i came along sofar have in  
> common.
>
> My trys sofar gave teh proove that fixing/hacking that behavior  
> indeed makes everything more 303ísh...but the way i patched it is  
> not optimal...
>
> I would enjoy if others have a look on this item and maybe come up  
> with some smart ideas to handle that.
>
> just using the mod envelopes to mimic the rise in decay times is  
> one option...but it would be more elegant to patch what is really  
> going on there..
>
> this is because of the accent sweep circuit that is involved in the  
> game at a later point and reffering to the biasing of the enevelope  
> pretty much...
>
> So question 1)
> Anybody has ideas to solve this 303 crosswordpuzzle?
>
>
> The "new 303 0.5" patch has a DIY envelope ...
> It at least behaves a bit in the direction i want it to be and  
> shows that diy env´s can be interesting... it plays somehow nice..
>
> So question 2) any better ways of doing DIY envelopes?
>
>
> regards
> Sven
> <new 303 0.5#.pch2>
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--
Rodge
http://www.rodge.com.au

Greetings from my new Powerbook