[Re: PolyModular]

[Rene Schmitz]

Hi Harry,

>Harry Bissell: The "autotune" routines that I'm familiar with don't work
quite
>this way... They measure the output frequency at several points across the
>frequency range (pll if you like) and then the sharp-flat correction data is
>stored in RAM (counters if you like). This is dynamically applied
>(interpolated data) across the range. 
>    The rub is... The circuit has to know what note you are attempting to
>play. If it is from the keyboard, and read by a MICRO, then the DAC value is
>"pre-corrected". But if the control comes from an ADSR or LFO, the circuit
has
>no way of knowing which correction factor to use (unless it is going to
>digitize the CV input.

I think if you use VCOs that have a sufficiently good tuning curve the
described circuit is all that is needed. The autotune that does scale
correction would be too complicated. I guess it was done in this way in many 
polysynths, because you can use simpler (and cheaper) expo-convertors,
witch need not be ultra precise and temperature stable. 

The proposed circuit just gets rid of the annoying tuning task. Witch would
be complicated because you don't have a fine tune pot for each VCO, and we
would not open up the unit every few months to retune all the oscillators.
(Ok, a few multiturn trimmers accessible thru holes in the frontpanel would
do perhaps.)

Bye
 René

             ,   : (uzs159 at uni-bonn.de)
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