[sdiy] VCO Accuracy

[Grant Richter]

The Korg Polysix manual gave a +/- 5 cent max deviation over the 4  
octave keyboard length as a production goal.

Kayfax Omnibus lists the total sales of the Korg Polysix at 30,000  
units.

At One volt per octave, one cent is 83 microvolts.

Measuring things (Metrology) is a scientific study in itself. Your  
test equipment most likely your largest source of error, unless you  
can afford a NIST traceable calibration yearly. And, unless you have  
at least one or two digits after the millivolt digit, the millivolt  
digit on your meter is probably wrong by +/- who knows millivolts.  
Thermocouples formed by dis-similar metals in meter probes and  
terminals generate error voltages relative to temperature in the  
microvolt range. Real world stuff like that goes on and on. It can  
drive you nuts ha, ha...

The most accurate piece of test equipment you have, is probably your  
ears.

On Dec 30, 2007, at 7:44 PM, Seb Francis wrote:

> Within 1 cent accuracy is good to aim for, although you are  
> unlikely to get there with analog.  A good MIDI to CV should be  
> capable of this - that's within ~1mV at 1V/Octave.  Of course  
> you'll need a good voltmeter to actually measure this.  I doubt any  
> analog VCO (even MOTM) will be much better than +/- 5 cent across  
> the useful musical range.
>
> Seb
>
>
> Tom Adam wrote:
>> A noob question about VCO's...
>> How accurate does one calibrate a midi 2 CV unit (+/-0.001V)?
>> How accurate does one calibrate a VCO? (+/-1Hz)
>> I understand that the accuracy is limited by design, but what is  
>> the "allowed" deviation before our human ear detects the error?
>>
>> I'm about to calibrate a MOTM 300 & 310 and an oakley VCO.  
>> Although I've tuned them after building I'm looking to get all 3  
>> of them in "perfect" tune.  Is there an easy way to accomplish this?
>>
>> Thanks,
>> ToAd
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