[sdiy] Oberheim Xpander Envelopes and LFOs etc

[ASSI]

On Sonntag 30 September 2007, 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).

There was a "speedmod" upgrade to increase the sampling rate of the 
envelopes (but that also made them shorter).

On Sonntag 30 September 2007, Tristan Upton wrote:
>  From what I recall, the Xpander uses a control voltage update rate
> of around 100Hz. To get around the problem of slow updates the
> control voltage sample and hold has two time constants. One is used
> for fast updates, like sawtooth reset, and a slower one for
> everything else.

The WAVE uses a a similar "trick" but uses the switchable output 
impedance feature found on the 5510 octal mux, which means that these 
have to be carefully matched...

On Sonntag 30 September 2007, Scott Gravenhorst wrote:
> Nonsequitur comment: FPGA does this without breaking a sweat and with
> far more slow objects than 4 and at sample rates beyond human
> hearing...

16x16-stage envelopes with looping and sequential triggering @40kHz 
update rate each plus a host interface to a ColdFire feeding the 
registers plus two 30MHz SPI interfaces to two 40-channel DACS in a 
FLEX10K20.

FWIW, the Waldorf Q uses an update rate of around 2.6kHz for Env and 
LFO.  Fast modulations are computed at the same speed, Slow modulations 
(in the matrix) I believe at half that rate.


Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk]>+

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