[sdiy] monolithic VCO chips for FM??

[synthplayer88 at spymac.com]

On Sat Aug 21 11:48 , harrybissell <harrybissell at prodigy.net> sent:

>synthplayer88 at spymac.com wrote:  
>
>> I think all modular control keyboard should have a pot for each key to fine tune
>> the control output voltage in order to nail the note frequency for precision, may
>> be this is already available and I am just unaware of this? or may be in midi?
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>
>I had such a system (PAiA 2720) which is admittedly a crude approach.... but you
>would have
>a more stable system with precision fixed resistors... or if you want to be really
>sure... an
>accurate DAC with a table of tuning offsets.
>
>Temperature stability and no long term changes with age and vibration would make the
>trimpots a tough choice. Calibration of such a system could be a nightmare.
>
>When I switched to 1% resistors... all my troubles disappeared.  Today with 1%
>resistors
>at $4/200... you could match yourself and get .1% easily.  Good enough !
>
>H^) harry
>
>


Well, the potentiometer per note approach would be a necessity if you were to use
those VCOs that does not work in pitch so you can tune each note on all the other
octaves where double or 1 volt DC increment won't get you double the frequency.....
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