[sdiy] MIDI VCO Control - but not CV?

[cheater cheater]

What could be done to circumvent the problem of the shapers that
create the sines?
Cheers

On 7/15/08, harrybissell at wowway.com <harrybissell at wowway.com> wrote:
> OK I get the idea about the pulse generator.
>
>  There is a Roland DCO that uses a micro output to generate
>  an approximately correct current value to charge a capacitor
>  to full voltage at the desired frequency  (higher frequencies need
>  more charging current) and then makes a Digitally controlled
>  reset pulse.
>
>  Any inaccuracies in the analog section therefore become errors of
>  sawtooth amplitude, not of frequency. Your ear is much more sensitive to
>  frequency than amplituce, so its a useful trade.
>
>  You would never hear this in a sawtooth, or a pulse derived from that
>  saw. In one case its a small error in pulse width (probably being PWM
>  anyway) or a small error in amplitude.
>
>  Try and use that sawtooth in a waveshaper (convert to triangle, or sine)
>  and the shape errors cause MAJOR changes in the harmonic structure...and these
>  waves have very little harmonics so the difference is really obvious
>  (sticks out like a sore thumb...)
>
>  If you got the control current really close, the error could be minimized...
>  and this would be useful in a poly-synth especially. Trying to retrofir this
>  to a conventional VCO core is certainly possible, but not with just a precise
>  reset pulse. You need CV to be close, anyway...
>
>  H^) harry
>
>
>
>
>  On Tue, 15 Jul 2008 14:57:18 +0100, cheater cheater wrote
>
> > Harry,
>  > this is not about midi sync.
>  > This is syncing to a pulse generator that has the pitch dictate by
>  > the incoming midi note.
>  >
>  > Also, this is about trying to sync the core only - shouldn't that
>  > work well? The later shaping etc that goes into making the
>  > triangle/saw a sine wave would work as usual...
>  >
>  > Cheers
>  > Damian
>  > On 7/15/08, harrybissell at wowway.com <harrybissell at wowway.com> wrote:
>  > > Hard-sync of a VCO would be VERY noticible...
>  > >
>  > >  A sine wave with even a tiny notch in it is extremely audible !!!
>  > >
>  > >  Midi sync would not have the speed to reset often enough...
>  > >
>  > >  If you did good MIDI to CV and added some sync it might work, but for that
>  > >  effort a better MIDI to CV converter would be the best use of the time and
>  > >  money IMHO...
>  > >
>  > >  H^) harry
>  > >
>  > >
>  > >
>  > >  On Mon, 14 Jul 2008 18:44:12 +0100, cheater cheater wrote
>  > >
>  > > > Hi guys,
>  > >  > Looking at the SDIY08 photos, I was wondering about MIDI2CV modules
>  > >  > and the problems they're (normally) having.
>  > >  >
>  > >  > Wouldn't it be *much* easier to make a midi2trigger module, that
>  > >  > would then hardsync the VCOs?
>  > >  >
>  > >  > You wouldn't necessarily get bad jitter, since the MCUs work at 10s
>  > >  > of MHz nowadays... that's enough resolution even for the best
>  > >  > 'golden ears' 8^)
>  > >  >
>  > >  > This could also mean easier microtunings (?)
>  > >  >
>  > >  > Are there any popular/interesting VCO designs that wouldn't work well
>  > >  > with being synced this way?
>  > >  >
>  > >  > How extremely difficult would it be to make a filter track pitch
>  > >  > like this?
>  > >  >
>  > >  > Having asked that, a filter's pitch is nowhere near as important as a
>  > >  > VCO's, so it could probably use 'traditional' MIDI methods anyways :)
>  > >  >
>  > >  > Just wondering what the synth diy gurus here think about this.
>  > >  >
>  > >  > Cheers
>  > >
>  > > > _______________________________________________
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>  > >
>  > >
>  > >
>  > > Harry Bissell & Nora Abdullah 4eva
>  > >
>  > >
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>
>  Harry Bissell & Nora Abdullah 4eva
>
>