[sdiy] 1V/OCT

[Guillaume Fairfield]

Hmmm,
0-10V?

Why not make it ±5V? Covering the same 11 octaves with the advantage of 
being able to be controlled by something other than a keyboard, like an 
LFO sine wave or something. Unless of course the plan is to bias at 5V.

Thanks

G.

Tim Parkhurst wrote:

>Hi Guillaume!
>
>Yes, you basically have it right. In a 1V/Octave synth, changing the control
>voltage to the VCO by +1 volt will raise the VCO frequency 1 octave. I don't
>really know if there is an established "middle frequency", although if you
>wanted to cover the entire audio range you might try
>
>0V = 20Hz
>1V = 40
>2V = 80
>3V = 160
>4V = 320
>5V = 640
>6V = 1280
>7V = 2560
>8V = 5120
>9V = 10240
>10V = 20480
>
>Most VCOs use a CV range of 0 to +10 volts, and many will respond to
>negative control voltages by producing even lower frequencies. Another name
>for 1v/oct is "exponential response". This is the standard used by most
>analog synthesizers. The other type of response is Volt/Hertz or "linear
>response". This is the scheme used by some of the earlier Japanese synths
>(early Korg like the MS-10 and MS-20, Roland like the 100 series). With a
>linear VCO, you might get something like 5V = 500Hz, 6V = 1000Hz, 7V =
>1500Hz, 8V = 2000Hz and so on. Linear response was also used in the first
>Moog Taurus pedals and is still used in the PAIA Fatman. Linear VCOs are
>easier to build, but they have several disadvantages - the most obvious
>being that they are not transposed as easily. Think about two or three VCOs
>in a system, each running at a slightly different frequency: with
>exponential VCOs, you can transpose all of them up one octave by simply
>adding 1 volt to the CV; with linear VCOs, each VCO will have to receive a
>different CV to move it up one octave. This is not to say that linear
>response systems are not useful. It's just that exponential response is much
>easier to work with (from the user's point of view), especially in a modular
>system.
>
>Hope this all makes sense. Like I said, you basically have it right. 
>
>
>Tim (easily transposed) Servo
>
>"Imagination is more important than knowledge." - Albert Einstein
>
>
>
>
>  
>
>>-----Original Message-----
>>From: Guillaume Fairfield [mailto:gfairfield at rogers.com]
>>Sent: Wednesday, March 10, 2004 11:06 AM
>>To: synth-diy at dropmix.xs4all.nl
>>Subject: [sdiy] 1V/OCT
>>
>>Hello all,
>>
>>I'm also new to this whole synth building business and am trying to
>>build my first vco. I think I have a plan but I'm unsure of to the whole
>>1V/OCT thing.
>>What's the standard? Is it that +1V gives an octave higher or lower? And
>>what's the middle frequency? In other words what frequency represents
>>0V? Maybe I'm missing something but that's the biggest piece of the
>>puzzle left, apart from all the math.
>>
>>Thank you for this list...I think I'm gonna learn alot here.
>>
>>guillaume
>>
>>
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