[sdiy] Cheap frequency counter for oscillator calibration

[thx1138]

On 4/23/10 1:12 AM, "Florian Anwander" <fanwander at mnet-online.de> wrote:

> Hello Terry
> 
>> 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.
> 
> The tune fork comes in when you want to setup the absolute tuning of the
> oscillator.
> 
> But in regard of the workflow of setting the octave width a tune fork
> has the same problem as the frequency counter. David Brown described it
> very well as "you're just chasing your tail as both frequencies shift".
> While setting the ocatve spread you have to concentrate on the relative
> tuning in the (multi-)octave jump. This can be controlled very good by a
> trained ear.
> 
> Though I have a really good hearing (I can tune a piano by ear quite
> well), my experience is that adjusting the octave width a polyphonic
> synth is extremely much faster with the described method using a
> chromatic guitar tuner.
> 
> While a piano basically is already at the right coarse tune, the VCO can
> slip through three or four notes when setting the octave spread. This is
> a completely different strain to the hearing than listening to a detuned
> piano.
> 
> Florian
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Hi Florian,

I use a small box I built that has a crystal based circuit with Dividers for
A-440 and Octave switch to set the base freq. On my Modular.

Once I have that set then I make sure v/octave source is plugged in to VC
input.

I have a test fixture I built for VCO/VCF calibration btw.

Then I assemble the unit and put the E-Mu polykeyboard 4065 in unison and
make sure VCO/VCF track the keyboard.

Another thing I do is I use 100k 1% resistors on the VC inputs that are
super matched. This way I get minimal error.

Most people have enjoyed my modules in the past, so I guess I have done a
few things right but I get a real kick out of how others get things done. I
always learn something new from folks.

But at the end of the calibration I still use my Peterson Strobe tuner for
calibration. It just works !!

I find I really only need about 5-6 octaves of really great tuning on my
synth anyway. I have written some software for my E-Mu polykeyboard so I can
do different tunings, but to be honest it got sort of a pain and I doubt I
still any use for such stuff today.

I need to re-design the 4065 E-Mu system to out put Midi stream along with
Gate and CV to trigger my Akai S-5000/6000 samplers.

Perhaps I can start a new batch of Module this year and let you guys beat me
up some more. I must complain about the lack of analog components being
available these days.

As I work for Freescale, I don't believe in all digital experience using
DSP's even though I have been responsible for so many DSP's indirectly and
directly.

But that is another thread I suppose along with vacumn tube based analog
synth's.

Where are you based Florian? I am in the Los Angeles area. It has been great
to get to know so many of you guys this last couple of years.

Regards,

Terry