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Coriolis
Joined: Apr 11, 2005
Posts: 616
Location: Stilling, Denmark
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 Posted: Thu Aug 07, 2008 12:43 pm Post subject:
Fixed! Yusynth wavefolder - calibrating trouble
Subject description: Dumb, dumber, DIY! |
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Just finished a Yusynth wavefolder, and have attempted to calibrate it.
Don't have a scope, so I thought I would try doing it by ear.
Well, according the the calibrating notes here:
http://yusynth.net/Modular/EN/WAVEFOLDER/index.html
- I should first tweak for sine symmetry with trimmer A1.
well - it does nothing. Nothing happens when I turn A1
- Then to trim cv response. I'm following instructions, but can't mute the signal completely. I can turn it down some, but it is still quite audible.
Then I thought of something I read on the site:
| Quote: | the third part is a level amplifier which gain is set to obtain an ouput signal in the range -10V to 10V.
By the way, if you need to modify the voltage range of the input and output signals, it is just a matter of changing the values of R20 & R21 for the input signal and that of R17 & R18 to adjust the output level. |
Eh? Is that 20V PP? Surely, he must mean -5v to +5v?
But if it is 20V PP, then it might explain some of the above problems, plus another thing:
Turning the Shape and Range pots do funny things as well.
No smooth increase/decrease of effect or whatever, but instead a bumpy ride from many overtones, to few, to many again.
Is something overdriving here perhaps?
I'm hoping someone who has built the thing can chime in here... 
C
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Last edited by Coriolis on Sun Aug 10, 2008 11:10 am; edited 1 time in total |
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yusynth
Joined: Nov 24, 2005
Posts: 1314
Location: France
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Posted: Thu Aug 07, 2008 1:48 pm Post subject:
Re: Yusynth wavefolder - calibrating trouble
Subject description: ...and a few questions |
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Hi Coriolis
| Coriolis wrote: | Just finished a Yusynth wavefolder, and have attempted to calibrate it.
Don't have a scope, so I thought I would try doing it by ear.
Well, according the the calibrating notes here:
http://yusynth.net/Modular/EN/WAVEFOLDER/index.html
- I should first tweak for sine symmetry with trimmer A1.
well - it does nothing. Nothing happens when I turn A1
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Whell it's quite normal that without a scope you can't get the sine distorsion (which is slight) by ear it's hardly feasible. By the way, are you listening by peeking the signal at the output of the VCA (where it must be done) or at the output of the module (where it's pure nonsense) ?
| Coriolis wrote: | - Then to trim cv response. I'm following instructions, but can't mute the signal completely. I can turn it down some, but it is still quite audible.
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This is not normal, it should mute. If not there is something wrong with your component, soldering or circuit. Check very thoroughly the component values (resistors mainly).
| Coriolis wrote: | Then I thought of something I read on the site:
| Quote: | the third part is a level amplifier which gain is set to obtain an ouput signal in the range -10V to 10V.
By the way, if you need to modify the voltage range of the input and output signals, it is just a matter of changing the values of R20 & R21 for the input signal and that of R17 & R18 to adjust the output level. |
Eh? Is that 20V PP? Surely, he must mean -5v to +5v? But if it is 20V PP, then it might explain some of the above problems,
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No I mean this exactly, the module can be used with a LFO to produce weird CVs and in my system I use 20Vpp for these kind of CVs. This is also why I suggest to change these values if one uses a different standard. By the way this is not an explaination for your problems.
| Coriolis wrote: | plus another thing:
Turning the Shape and Range pots do funny things as well.
No smooth increase/decrease of effect or whatever, but instead a bumpy ride from many overtones, to few, to many again.
Is something overdriving here perhaps?
I'm hoping someone who has built the thing can chime in here...
C |
Well as a matter of fact if the first stage (i.e. the internal VCA) is not set correctly don't expect the following part of the circuit to work either. You must first fix that VCA part.
You may send me detailed photos of your PCB and I will check and see if I can see some anomalies.
Cheers
Yves
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Yves |
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Coriolis
Joined: Apr 11, 2005
Posts: 616
Location: Stilling, Denmark
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| Posted: Fri Aug 08, 2008 2:20 am Post subject:
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Hi Yves 
Thank you for the pointers.
From what you say, it might be an issue with the vca.
I only matched the transistors for hfe, which perhaps isn't accurate enough.
Will try with a proper matched pair (LM394) instead.
I suppose there is no reason to adjust A1 then, if it is hardly audible what it does.
I have matched the diodes in pairs as close as I could, but some may be a couple of mV apart. Would that cause a lot of trouble?
And...sorry for being ignorant, but what resistor values would I put in place of R20-R21 and R17-R18 if I want 10V PP operation?
Thanks again,
C
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yusynth
Joined: Nov 24, 2005
Posts: 1314
Location: France
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| Posted: Fri Aug 08, 2008 2:51 am Post subject:
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| Coriolis wrote: | Hi Yves
Thank you for the pointers.
From what you say, it might be an issue with the vca.
I only matched the transistors for hfe, which perhaps isn't accurate enough.
Will try with a proper matched pair (LM394) instead.
I suppose there is no reason to adjust A1 then, if it is hardly audible what it does. |
No Hfe matched trannies are accurate enough, in my opinion the setting of A1 is a minor refinement which is not actually useful for a circuit that comes before a wavefolder 
| Coriolis wrote: | I have matched the diodes in pairs as close as I could, but some may be a couple of mV apart. Would that cause a lot of trouble?
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It's perfect...
| Coriolis wrote: |
And...sorry for being ignorant, but what resistor values would I put in place of R20-R21 and R17-R18 if I want 10V PP operation?
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Make R21 = 1.2K and R18 = 27K.
My main concern comes from the fact that you cannot mute the signal by adjusting A2.
As I said you may send me a photo of your PCB (component side and track side) such that I can check for errors : yves"dot"usson"at"yusynth"dot"net (replace "dot" by . and "at" by @ )
Cheers
Yusynth
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Coriolis
Joined: Apr 11, 2005
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Coriolis
Joined: Apr 11, 2005
Posts: 616
Location: Stilling, Denmark
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| Posted: Sun Aug 10, 2008 11:23 am Post subject:
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Just an update...
Yves has really gone out of his way (or so it seems to me) to help me on this one. I took him up on his offer and mailed him pics of the board I made.
He soon spotted a couple of incorrectly inserted transistors... 
I don't have to tell you how many times I checked and double-checked the pinout of those darned things before soldering them in, but there you go.
Well, I can tell you that you get funny performance from this circuit if you make that mistake, so that's a place to look, if something acts up.
After I fixed that, I still had trouble calibrating the circuit to shut off all sound, when cv is at minimum. Turns out there was a slight typo in the schem at Yves' site (mis-labeling of pots), which was causing the confusion.
I believe he has corrected that.
Lastly, a potential mod/tweak:
I found the Shape pot to have a sweet-spot circa mid-travel, where pretty much all the action happens. So I tried substituting a 20k pot (50k originally) to get more even change when turning the Shape control.
There was noticeable improvement (for my tastes anyway), and I would have left it in there, had it not been center-detent, which was, uh...weird in use...
Well, that's all - I'll be folding waves if you need me...
Thanks again Yves - you are great!
C
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yusynth
Joined: Nov 24, 2005
Posts: 1314
Location: France
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| Posted: Sun Aug 10, 2008 11:43 am Post subject:
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Hi Coriolis
I fixed the typo on my site thanks to you 
Great to ear that you wavefolder rocks.
And to quote Hannibal Smith: I love it when a plan comes together
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