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Erica Synths Polivoks VCO II squaring up the pulse
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Erica Synths Polivoks VCO II squaring up the pulse
mattip
Does anyone know if it is possible to calibrate the pulse wave and possibly the saw tooth on the Erica Synths Polivoks VCO II? They look a bit off, though I didn't actually hear a problem.
I just used an app in my iPhone connected through iRig 2 interface. I have no idea if the waveforms in the app actually shows something that is worth calibrating with. But I don't have a working oscilloscope right now.

Triangle:


Saw:


Pulse:


/m
GilgaFrank
mattip wrote:
They look a bit off, though I didn't actually hear a problem.


Do you intend to listen to them or look at them?
mattip
GilgaFrank wrote:
mattip wrote:
They look a bit off, though I didn't actually hear a problem.


Do you intend to listen to them or look at them?


Both! This is my first and so far only vco. I use the oscilloscope app to learn what happens.

Btw, I tried the three trimmers on the component PCB. No change in waveform.
Randy
GilgaFrank is telling you something important. I really doubt you would hear any difference between the waveforms you're seeing and a perfect version. Also, since this is a Polivoks, what you're seeing may actually be correct for duplicating the Polivoks.

If you want more accurate waveforms, get a newer-style VCO. In an obvious case of self-interest and helping a friend, I can recommend this one:

http://www.youtube.com/watch?v=3Jteyx1KTfc&t=5s
mattip
It might of course be that polivoks have different waveforms. But here is a video where it looks like the waveforms are much more square than mine. https://youtu.be/djZjjaTktLo about 6 min in.
Since I am so new at this (went from zero to building eight modules in eight weeks) the first thing I think is “what did I screw up now?” So I really try to check everything out in detail.
Btw, have looked a lot at PM foundations modules. Especially the sequencer.
/m
TOPLEL
I think the falling top of the square is due to the high pass filtering somewhere in the iRig interface. (coupling caps) Is it DC coupled? What is the freq response? I guess your waves would look better in a "real" scope with a higher bandwith. (like from DC/0hz to Mhz) My waves look similar using my 20hz to 16kHz audio interface.
mattip
TOPLEL wrote:
I think the falling top of the square is due to the high pass filtering somewhere in the iRig interface. (coupling caps) Is it DC coupled? What is the freq response? I guess your waves would look better in a "real" scope with a higher bandwith. (like from DC/0hz to Mhz) My waves look similar using my 20hz to 16kHz audio interface.


Interesting! Yes, that might be the answer. Will try to recheck with a real scope soon.

/m
standudinski
That square looks fine. A lot of analogue VCOs display that sort of tendency. That's what gives me character.
Matter of fact, all the waveforms looks as they should. i have the same VCOs and they draw exactly the same graph on my oscilloscope.
mattip
So, got myself a real scope. This is what it showed!

Can someone explain why the iRig + iPhone showed the wrong waves?



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