[sdiy] VCO control Range

[Jerry Gray-Eskue]

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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