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 Forum index » DIY Hardware and Software » YuSynth
Need help with YU-Synth Arp 4072 VCF
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yusynth



Joined: Nov 24, 2005
Posts: 1314
Location: France

PostPosted: Mon May 13, 2013 4:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Check earlier in this thread, I gave some clues to debug problems (measurement points and so on). Have you tried to change the LM3900 ?
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Yves
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sylvainmoreau



Joined: Feb 19, 2013
Posts: 17
Location: paris

PostPosted: Mon May 13, 2013 5:38 am    Post subject: Reply with quote  Mark this post and the followings unread

no i haven't changed the LM3900 i didn't do any test for now, i need a voltage generator :p do you recommand some nice tool to do that ?
like something like this would be ok ? :
http://www.selectronic.fr/calibrateur-de-tension-et-de-courant.html

i have an oscilloscope and multimeter .. guess that should be enough to test all the basic audio DIY i'm doing.

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yusynth



Joined: Nov 24, 2005
Posts: 1314
Location: France

PostPosted: Mon May 13, 2013 6:58 am    Post subject: Reply with quote  Mark this post and the followings unread

An oscilloscope and a good multimeter are all that is required.
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sylvainmoreau



Joined: Feb 19, 2013
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PostPosted: Mon May 13, 2013 7:32 am    Post subject: Reply with quote  Mark this post and the followings unread

ok but for calibration procedure .. you need to generate 1V right ?
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yusynth



Joined: Nov 24, 2005
Posts: 1314
Location: France

PostPosted: Tue May 14, 2013 12:03 am    Post subject: Reply with quote  Mark this post and the followings unread

It's easy a simple potentiometric circuit does it: it's a matter of connecting a 12K resistor and a 2.5K 15 turns trimmer in series between +15V and 0V (trimmer connected to 0V, resistor to the +15V) and adjusting the trimmer until 1V is measured on the taper of the trimmer.
If you wnat to be perfect you may add an OpAmp mounted as buffer (volatge roller) betwen the taper of the trimmer and the output.

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sylvainmoreau



Joined: Feb 19, 2013
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PostPosted: Sat Jun 08, 2013 4:39 am    Post subject: Reply with quote  Mark this post and the followings unread

ok finally i calibrated my filter and it works.
but i have a strange sound happening like if i had a little envelope doing some gate at attack release.
so here is a demo first sound is ARP filter up and down then the MOTM440 up/down.
settings are :
square sent to ARP
FREQ 0->full->0
RESO 0%
in1 70%
in2 0% (not connected)
cv1 0% (not connected)
cv2 0% (not connected)

i found strange that "clip" sound on the arp that stays even if the filter is 0. any idea on what does this sound ?
here is a picture of the waveforms


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

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sylvainmoreau



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PostPosted: Wed Jun 12, 2013 1:50 am    Post subject: Reply with quote  Mark this post and the followings unread

no ideas ? Posted Image, might have been reduced in size. Click Image to view fullscreen.
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Benjamin AM



Joined: Nov 04, 2010
Posts: 83
Location: Boise

PostPosted: Wed Jun 12, 2013 3:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

I believe what you are experiencing is filter bleed through. There is a way to fix this by installing a dual gang pot. I know that there is information on this subject somewhere in the forum.
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sylvainmoreau



Joined: Feb 19, 2013
Posts: 17
Location: paris

PostPosted: Wed Jun 12, 2013 4:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

dam .. thx for info i'll search for that but the problem on the forum is that when you enter a keyword in search it opens the topic from page 1 (!) and most of them have lots of them :S
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Benjamin AM



Joined: Nov 04, 2010
Posts: 83
Location: Boise

PostPosted: Wed Jun 12, 2013 6:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

http://electro-music.com/forum/viewtopic.php?highlight=bleedthrough&t=47802
I would suggest to read the entire link
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sylvainmoreau



Joined: Feb 19, 2013
Posts: 17
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PostPosted: Thu Jun 13, 2013 12:54 am    Post subject: Reply with quote  Mark this post and the followings unread

how thx Benjamin i missed that one Laughing
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kx



Joined: Dec 05, 2009
Posts: 17
Location: New Zealand

PostPosted: Tue Dec 30, 2014 4:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi All,

I've been trying to get my Yusynth ARP-VCF running properly for quite a while now and I've hit a bit of a wall, so I was wondering if any of you might be able to help.

It's a PCB that I've toner-transfered, and it's the 2n3906 version. My problem is that the signal that enters the board just passes through and is not filtered. I've tried replacing the LM3900N with a new one, and I've replaced all of the transistors with matched 2n3906s (in the correct orientation).

Referring to the tests from the first page of this thread, the voltage measurement at the Q6 junction ranges from -6.4v to -6.7v which isn't the same but not too far off from what Yves and Luka had. When inputting a +/-4v square wave with the resonance pot at 0 and frequency pot at 12, I read a -5v to -10v square wave at all four of the filter poles with no sign of filtering.

Does anyone have any idea what could possibly be at fault?

Thanks a lot.
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