[sdiy] Polyphonic temp compensation in VCF's!

ChristianH chris at chrismusic.de
Tue May 24 10:39:18 CEST 2011


On Mon, 23 May 2011 23:37:33 +0100 (BST) karl dalen <dalenkarl at yahoo.se> wrote:

> -- Den mån 2011-05-23 skrev Tom Wiltshire <tom at electricdruid.net>:
> 
> > Many of the synths you mention that *don't* have tempcos
> > for the filter will use an autotune routine instead. So if
> > you think the filter FM sounds 'out of tune', you can just
> > bang the autotune button - at whatever temperature.
> 
> The autotune in those machines as i have understod them
> are probably multi pass all parameter tuning method, not
> continuous background single parameter periodical tuning
> method (compare with A6) which would make sense. If that
> actually works? Anyhow, in many cases are slow on the
> 8Mhz Z80 of the day.
> 
> So slam the auto button dont seem like a viable method
> to me, well if it would they should have not put in
> tempcos in the first place i reasoning.
> 
> OBmx are a resonable new design has no tempcos but FFM
> it would have been interesting to se how auto tuning
> works on the 2 discrete filters.

Set one filter to flat response, the other to self oscillation, and then
feed the input of the (closed) VCA to a 393-or-whatever comparator?

Christian



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