[sdiy] VCO - Saw and Ramp Outputs

[David G. Dixon]

Tim,

In the Thomas Henry circuits I have built, I've always made provision on my
PCB layouts for adding resistors between the power supply rails and the
control pots.  Sometimes I put wire jumpers in these locations, and
sometimes I put in resistors.  However, in most cases, for things like
coarse frequency tuning and filter resonance control, I'll put in resistors
to limit the play to the audio range (at least on the top end) or just
beyond, while on fine adjustments I'll go with jumpers and a large
range-limiting resistor of the pot tap into the summer.  This seems to work
well for me, and I've had no problems achieving the correct ranges for CV
inputs of various polarities.  I guess I find it annoying when a coarse
tuning pot only gives audible results between 10 o'clock and 2'oclock, but
to each his/her own!

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of Tim Parkhurst
> Sent: Monday, June 01, 2009 12:19 PM
> To: Jerry Gray-Eskue
> Cc: Synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] VCO - Saw and Ramp Outputs
> 
> On Mon, Jun 1, 2009 at 5:51 AM, Jerry Gray-Eskue <jerryge at cableone.net>
> wrote:
> >
> > Hello All,
> >
> > Should the Saw and Ramp waveforms forms from a VCO used as the Audio
> Signal
> > source be centered on Ground (i.e. -5v to +5v) or is it just as well
> that
> > they run in the 0v to + 10v range?
> >
> > What about a Low Frequency VCO used as a CV source, is it the same
> setup?
> >
> > Jerry
> >
> 
> Well, here's my take: For audio use, the waveforms should generally be
> centered around 0V, as a DC offset can cause problems when mixing or
> switching audio. For CV use, it just depends on what effect you want.
> Vibrato generally needs a wave centered around 0, while a trill needs
> a 0 to +5 wave. On most CV inputs, you'll have an "Initial" setting
> pot (hooked up to -V and +V) which can be used as offset to get the
> modulation centered where you want, and a "Mod Level" pot (hooked up
> as an attenuator) that will control the level. On many CV inputs (like
> my Mankato or Sheboygan CV inputs), the Initial pot will have more
> range than the core circuit can respond to, but the extra range is
> handy for offsetting CVs.
> 
> 
> Tim (handy for other stuff) Servo
> --
> "Sire, the church of God is an anvil that has worn out many hammers."
> - H.L. Hastings
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