[sdiy] Oberheim Xpander Envelopes and LFOs etc

[Richard Wentk]

On 30 Sep 2007, at 12:56, Tom Wiltshire wrote:

> I suspect this is one of the areas where corners can be cut far  
> more than most people would accept. The Waldorf Wave also uses  
> software envelopes, and these are only updated at about 53Hz!  
> (http://www.unofficial.waldorf-wave.de/wavetech.html). Yet the Wave  
> is held in high regard. If anyone could do a similar test on a  
> Oberheim Xpander, I'd be interested to know the result.

Playing catch-up - if the Wave is anything like the uWave, the slow  
envelopes are a big limitation.

I'd guess the Wave does so many other things that no one cared that  
the envelopes aren't clicky enough. But the slow envelopes on the  
uWave used to seriously frustrate me.

> So the question is "How low can you go?". 53Hz might be really  
> silly, but would 1KHz be enough? 5KHz? I know some of the software  
> sound languages (csound or puredata) use rates of 6KHz or so.

Csound has a completely arbitrary rate. You can run the istream at  
the same rate as the astream, if you want to. Or at 0.0005Hz.  
(Although you probably won't want to.)

> What counts as a reasonable sampling rate for LFOs and Envelopes?

I find with Reaktor that 1k is a good minimum. It's hard to hear  
transients faster than 1mS.

For smoother envelopes, you might want to multiply that by 5. 5k is  
probably a sensible maximum limit if you're worried about processor  
overhead, and audibly, there's not usually any need at all to go higher.

If you're not worried about processor overhead, run everything at the  
audio rate. Envelopes won't eat up as much CPU power as anti-aliased  
oscillators or good filters will, so this may not be as extravagant  
as it sounds.

Richard