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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Mon May 13, 2013 4:00 am Post subject:
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Check earlier in this thread, I gave some clues to debug problems (measurement points and so on). Have you tried to change the LM3900 ? _________________ Yves |
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sylvainmoreau
Joined: Feb 19, 2013 Posts: 17 Location: paris
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Mon May 13, 2013 6:58 am Post subject:
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An oscilloscope and a good multimeter are all that is required. _________________ Yves |
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sylvainmoreau
Joined: Feb 19, 2013 Posts: 17 Location: paris
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Posted: Mon May 13, 2013 7:32 am Post subject:
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ok but for calibration procedure .. you need to generate 1V right ? _________________ arp vcf 4072 in progress |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Tue May 14, 2013 12:03 am Post subject:
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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. _________________ Yves |
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sylvainmoreau
Joined: Feb 19, 2013 Posts: 17 Location: paris
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Posted: Sat Jun 08, 2013 4:39 am Post subject:
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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
_________________ arp vcf 4072 in progress |
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sylvainmoreau
Joined: Feb 19, 2013 Posts: 17 Location: paris
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Benjamin AM
Joined: Nov 04, 2010 Posts: 83 Location: Boise
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Posted: Wed Jun 12, 2013 3:12 pm Post subject:
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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
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Posted: Wed Jun 12, 2013 4:53 pm Post subject:
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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 _________________ arp vcf 4072 in progress |
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Benjamin AM
Joined: Nov 04, 2010 Posts: 83 Location: Boise
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sylvainmoreau
Joined: Feb 19, 2013 Posts: 17 Location: paris
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Posted: Thu Jun 13, 2013 12:54 am Post subject:
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how thx Benjamin i missed that one _________________ arp vcf 4072 in progress |
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kx
Joined: Dec 05, 2009 Posts: 17 Location: New Zealand
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Posted: Tue Dec 30, 2014 4:25 pm Post subject:
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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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