[sdiy] VCO control Range

[Laurie Biddulph]

But what about the link up with MIDI?

MIDI starts at 0V and goes up from there. It doesn't support negative 
voltages. So if you set 0V to equate to MIDI Note 0 (8.176Hz) then you can 
only work with positive voltages.

So we have our VCO set for 0V = 8Hz and then we connect a CV controller that 
has a range of -10 to +10V, what do we do with the negative voltages?

Best Regards

(Mr) Laurie Biddulph
Phone: +61 (0)2 4340 0938
Mobile: 0400 257 645

Elby Designs
ABN: 70 022 727 605
http://www.elby-designs.com

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----- Original Message ----- 
From: "Jerry Gray-Eskue" <jerryge at cableone.net>
To: <Synth-diy at dropmix.xs4all.nl>
Sent: Friday, August 28, 2009 11:44 PM
Subject: RE: [sdiy] VCO control Range


> Thanks,
>
> I think that clears up my confusion.
>
> So to summarize the valid input range is +10 to -10 volts limited by the
> capabilities of the VCO being used. The initial frequency is set at 0 
> volts
> and the VCO tracks frequency + and - from there at 1 volt per octave.
>
> Cool I appreciate the help,
>
> - Jerry
>
> -----Original Message-----
> From: JH. [mailto:jhaible at debitel.net]
> Sent: Friday, August 28, 2009 8:33 AM
> To: Jerry Gray-Eskue; Synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] VCO control Range
>
>
> Just as +1V means one octave up (2*f), -1Vmeans one octave down (f/2).
> -2V, 2 octaves down (f/4), and so on.
> You hit a limit somewhere at low frequencies, when leakage currents of 
> your
> circuit are in the same range as the current that
> charges the integration capacitor in the VCO - that current always goes
> "linear", so -5V means f/32, and also i/32.
> *Where* that limit is, depends on the actual VCO circuit.
>
> JH.
>
> ----- Original Message -----
> From: "Jerry Gray-Eskue" <jerryge at cableone.net>
> To: <Synth-diy at dropmix.xs4all.nl>
> Sent: Friday, August 28, 2009 3:09 PM
> Subject: [sdiy] VCO control Range
>
>
>
> This may be a silly question but I am do not have a clear idea of how this
> works.
>
> The 1 volt per Octave input on VCOs clearly means that if your input 
> voltage
> goes up one volt the frequency out doubles to be one octave up. Simple
> enough, the question is what is the real range of voltage VCOs work at?
>
> I see a number of references to calibrating a VCO using 0 volts and steps 
> of
> 1 volt above 0 volts like 0,1,2,3,... up to a max of 10 volts. So from 
> this
> it looks like a VCO is expected to track positive voltages up to its max
> range capability. What is not clear to me is if the VCO tracks Negative
> input voltages i.e. -1,-2,-3.. to -10 volts.
>
> Any help clearing this up will be appreciated.
>
> - Jerry
>
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