[sdiy] Cheap frequency counter for oscillator calibration

[thx1138]

On 4/22/10 6:28 AM, "Florian Anwander" <fanwander at mnet-online.de> wrote:

> Hi Karl
> 
>> I'm looking to buy a cheap ($50-$200) frequency counter mainly to be used for
>> calibrating the span and base tuning of analog oscillators - any suggestions?
>> Is there a better way of doing this then just measuring the frequency?
> To be honest: I would not recommend a frequency counter for spread
> tuning. In theory it would be ok, if you always tune the spread testing
> between the 0 Volt at the VCO-core and plus 1/2/... Volts. But in fact
> you will have always some kind of offset voltage at the output of the
> CV-mixer. This will cause the base frequency to be different with each
> change in the spread setting.
> This means for each turn on the spread you have to re-adjust the tune.
> 
> I prefer the following method:
> 
> Use a wide range chromatic tuner with a analogue meter like a Boss
> TU-12H (in fact the TU12-H is the only today available tuner which I
> would recommend).
> Connect the tuner to the output of the synth and listen to the synth
> through the headphone out.
> Now send (multiple) octave jumps and adjust the spread trimmer and
> whatch the tuner: It does not matter WHICH note exactly is displayed (it
> may be a completely different notes at different settings of the spread
> trimmer), but you trim it until you hear a clean octave and the meters
> needle does noe longer move when the octave jump happens. The absolute
> pitch of those two notes does not matter at that moment.
> When this is done I set the absolute pitch, and - if requires - the
> trimming of octave switches.
> 
> I recently tuned an OBXa (16VCOs !) in around 40 minutes with this method.
> 
> Flroian
> 
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Hi Guys,

Just for fun, Ever try using a tuning fork and your ears? It is a bit of a
work but the voicing is so much better on a piano.

I use a Peterson Strobe tuner that I have had for about 30 years and it
performs very nicely. I usually set the end to end v/0ctave to be exact as
possible using a 4 1/2 digit DMM. And make sure octave switches are not
throwing any offset voltages into the tracking.

Freq counter, it is possible but pretty sterile sounding results in my
opinion.

I guess it is a curse to have perfect pitch sometimes.

Just my 2 cents.

Regards,

Terry