[sdiy] Frequency Counter Software

[Seb Francis]

To answer my own question ...

I've tried a few different frequency counter / spectrum analyser / scope 
softwares (hopefully 'softwares' is acceptable english ;)
They all use FFT to get the frequency and don't seem to be very accurate 
- they jump around by a few hertz even with a stable input.

But thinking along different lines, I found this great little VST plugin 
"C-Tuner"
http://mitglied.lycos.de/moritz_48/Free-VST/cplugs11.ZIP

In 'super-accurate' mode it measures to 0.1 cents.

Testing with a soft-synth showed the expected 0.0 cent error
Testing with my nord lead (digital) hardware synth showed a consistent 
error of +0.4 cent across the whole keyboard .. I can live with that :)

Interestingly when I hooked up my MOTM VCOs, although they tracked well 
(within 5 cents across the whole keyboard - perhaps could be even better 
if I bothered fine tuning the trimmers a bit), both the 300 and 310 
showed a jitter of approx 2 cents.  This is not my MIDI2CV converter by 
the way - the jitter is still present even with nothing plugged into the 
CV input.

Now I'm not complaining: this is probably much better than most other 
VCOs (and actually one of the plus points of analog is the inaccuracy), 
but I make my point again about MIDI2CV converter accuracy - what 
benefit is there in having better than 1 cent accuracy if even a 
super-stable MOTM VCO is not this accurate.

Anyway, now off to tune my newly built Oakley 3031 .. which was what 
started all this in the first place!

Seb




ryan williams wrote:

> thats a good idea. I had been tuning VCOs by doing this:
> run a soft-synth at some frequency. also output the MIDI value to your 
> MIDI->CV converter. mix that with the VCO and listen to beats to get 
> the offset correct. then go up 2 octaves and adjust the scaling, 
> repeat. Sure this is a common method, but it shouldn't be too hard to 
> make a frequency counter (did one with an 8bit uC once). A neat 
> program would be something that plays a reference frequency mixed with 
> the VCO output and displays the VCO frequency at the same time. I 
> think I'll write this program. It'll be atleast 2 weeks though.
>
> -ryan
>
> Seb Francis wrote:
>
>> Hi,
>>
>> Can anyone point me in the direction of an accurate (and preferably 
>> free) frequency counter software for windows.
>>
>> It seems to me that this would be a very accurate and easy method of 
>> tuning VCOs (especially since my sound card is clocked from a dead 
>> stable RME A/D D/A interface).
>>
>> Seb
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