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 Forum index » DIY Hardware and Software » YuSynth
Yusynth Wavefolder troubleshooting
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Tue Apr 17, 2018 7:10 am    Post subject: Yusynth Wavefolder troubleshooting Reply with quote  Mark this post and the followings unread

Built and populated a Yusynth Wavefolder and I am quite happy about it. Merci Yves. Very Happy

I do seem to have a couple of issues. I tested it with my Fonik / Thomas Henry VCO-555 and using on board single turn VRs as that's what I had at hand. Now, the default TH VC0-555 has quite a low Sine output and I still have to mod that. Some settings I tried: VCO Tri into Wavefolder In, VCO Ramp into Wavefolder Control (really cool on some Pot settings!).

Issues:

1. The Shape Pot does sound like it is merely attenuating. I can also see the corresponding effect on my DSO scope.

2. An odd thing happens when I put my DVM +ve on the TL074 P6: my output buzzes (it is as if it now gets the Wavefolder effect out). I also find that when my hand is around the Shape wires or its pot, or just moving it around, that seems to also increase buzz on the output.

3. Both the Range and Control Pots sometimes go: 'No Sound/Low' to 'Big effect' and 'Back to No Sound/Low' depending on settings instead of an expected (IMO) smooth sweep from Nothing/Low to Large Effect.

I cleaned the board again today which seemed to help a bit. I also tested for continuity around the TL074 and R11, R14 and R15 and everything seems fine here.

I have 2 3904 transistors, so if I didn't mess this up, I used them 180 degrees rotated.
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Wed Apr 18, 2018 1:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Re-tested and re-calibrated. This time I removed my circuit linked to the 1V/Oct to see whether that was making any interference.

VR A1 doesn't seem to do much for me.

Shape still sounds like an attenuator.

I used Sine into Control over a Triangle at Input. It does look like it's wavefolding a little. First, Control to minimum:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

And the rest, as I increase the Control Amount:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Last edited by YashN on Wed Apr 18, 2018 4:04 pm; edited 1 time in total
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Wed Apr 18, 2018 1:34 pm    Post subject: Board pics Reply with quote  Mark this post and the followings unread

Hopefully all components are the right ones. There are 2 or 3 resistors values that I had to do some series combinations as I didn't have the exact values at hand.

How would I really check whether the VCA is working properly or what else should I check?

I left out the CV3 pads untouched.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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Grumble



Joined: Nov 23, 2015
Posts: 721
Location: Netherlands
Audio files: 21

PostPosted: Thu Apr 19, 2018 4:20 am    Post subject: Reply with quote  Mark this post and the followings unread

If you didn't used a 10x probe and these are output voltages, they are very low compared to http://www.yusynth.net/Modular/FR/WAVEFOLDER/wavefolderscope.html.

Also I see some differences according to the populated pcb:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

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marfoski



Joined: Jan 26, 2011
Posts: 36
Location: Italy

PostPosted: Thu Apr 19, 2018 7:14 am    Post subject: Reply with quote  Mark this post and the followings unread

IMHO, 1N4007 diodes are not a direct replacement for 1N4148, being rectifiers and much slower.

Just my two cents, tho
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Thu Apr 19, 2018 9:08 am    Post subject: Reply with quote  Mark this post and the followings unread

marfoski wrote:
IMHO, 1N4007 diodes are not a direct replacement for 1N4148, being rectifiers and much slower.


I don't think that explains why I get buzz on the output when probing the TL074 P6.

The issue should be elsewhere IMO. So far, I am thinking something could be bad around the VCA, or else the 1-turn VRs in lieu of the 10-turn trimmers aren't allowing me to calibrate properly.

Apart from that, I am using a +12V, 0, -12V PSU but I think that is OK with this module although output volume may vary.

For the resistors where I had to use 2 or 3 in series to approximate, these aren't specified as precision resistors IIRC, so that should be OK too.
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Thu Apr 19, 2018 10:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:
If you didn't used a 10x probe and these are output voltages, they are very low compared to http://www.yusynth.net/Modular/FR/WAVEFOLDER/wavefolderscope.html.

Also I see some differences according to the populated pcb:
Posted Image, might have been reduced in size. Click Image to view fullscreen.


What's up, Grumble. Yes, I have listed the differences where I can:

1. 3 areas where I used series resistors to approximate the resistor value.

2. Different diodes (shouldn't matter too much for the wavefolding operation but drop can be different and should probably be adjusted).

3. I am using this with a TH VCO-555, which if you don't dig into threads, then the output volume of the Sine is low and I still need to modify that. For now, that explains it. Volume is quite OK with other waveforms.

4. There are 2 3904 instead of BC547. These are the two which are close to each other. I have rotated them 180 degrees after double-checking the pin-outs.

5. 2 one-turn VRs instead of multi-turn trimmers

6. I have a 50K Lin Pot for Shape

Diodes were hand-matched with my DVM.

I also noticed some bleed when only the Control signal is patched in.
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Thu Apr 19, 2018 4:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:
Also I see some differences according to the populated pcb:
Posted Image, might have been reduced in size. Click Image to view fullscreen.


Can you point out these differences?
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wackelpeter



Joined: May 05, 2013
Posts: 419
Location: germany
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PostPosted: Fri Apr 20, 2018 10:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Apart from the diodes that are in the Feedback path of the OPamp and Point in the opposite direction but that wouldn't matter as they're in parallel, i only spotted the trannie on the upper left... when this is not an BC547 and an 2n3904 instead, shouldn't it be rotated by a 180 degree?
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Fri Apr 20, 2018 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

wackelpeter wrote:
Apart from the diodes that are in the Feedback path of the OPamp and Point in the opposite direction but that wouldn't matter as they're in parallel, i only spotted the trannie on the upper left... when this is not an BC547 and an 2n3904 instead, shouldn't it be rotated by a 180 degree?


It is a BC547.
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Hubaswift



Joined: Jul 06, 2016
Posts: 65
Location: Canada

PostPosted: Sun Apr 22, 2018 5:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

I don't see any problems with the part values. A picture of the bottom of the pcb would also be helpful.
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Grumble



Joined: Nov 23, 2015
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PostPosted: Sun Apr 22, 2018 9:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

bottom left resistor, should be 680ohm, you have 332ohm.
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Mon Apr 23, 2018 3:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:
bottom left resistor, should be 680ohm, you have 332ohm.


That should affect solely the input level directly I think. As stated on Yves' site:

Quote:
R21 680/330 ohms to selected depending on the input levels 1


and

Quote:
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.


The Shape Pot could be a bit suspect. I'll see if I can swap it for a new one.

There's a possibility I get the multi-turn trimmers today, so I can try those as well.
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YashN



Joined: Jun 27, 2011
Posts: 92
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PostPosted: Thu Apr 26, 2018 10:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Hubaswift wrote:
I don't see any problems with the part values. A picture of the bottom of the pcb would also be helpful.


Hey @Hubaswift, missed your post. Definitely a good idea. Will do that soon.
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YashN



Joined: Jun 27, 2011
Posts: 92
Location: Canada

PostPosted: Fri May 18, 2018 9:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Hubaswift wrote:
I don't see any problems with the part values. A picture of the bottom of the pcb would also be helpful.


Thanks for the feedback on the part values, @Hubaswift.

I have since put in the proper trimmers. Haven't swapped the Shape Potentiometer.

Here is a recent pic of the trace side:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Flipped PCB printout for comparison:

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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YashN



Joined: Jun 27, 2011
Posts: 92
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PostPosted: Sat Jul 21, 2018 2:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Any ideas?

How would I test only the VCA part to diagnose it and perhaps troubleshoot it if it's the culprit?
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