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sebsongs
Joined: Feb 09, 2013 Posts: 49 Location: Malmö, Sweden
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Posted: Sat Oct 26, 2013 4:06 am Post subject:
Steiner Parker filter weird behaviour. SOLVED! Subject description: Demo video + pcb pictures available. |
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I finished the Steiner Parker filter this week and got it up and running.
It behaves quite strangely though. It does filter the signal and all the controls seem to do what they should, but the ranges and behaviour are quite strange.
I shot a video with sound directly from the synth to show what I mean.
Beneath is also photos of the pcb.
All resistor values match the BOM, and I know some of them should be changed to calibrate the range of cutoff and resonance, but I feel there must be more wrong with this filter.
The trimmers on the PCB seem to do what they should, but I can't seem to dial it in.
Any help is much appreciated!
Video link:
http://www.sebsongs.com/wp-content/uploads/2013/10/synthacon_problem.mp4
In the video I compare the behaviour with the Minimoog filter, just for reference.
Photos:
Thanks in advance!
Sebastian Last edited by sebsongs on Sat Oct 26, 2013 11:36 am; edited 1 time in total |
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feggster
Joined: Sep 12, 2011 Posts: 52 Location: uk
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Posted: Sat Oct 26, 2013 10:02 am Post subject:
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i think c13 is reversed on the layout compared to the schem. |
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sebsongs
Joined: Feb 09, 2013 Posts: 49 Location: Malmö, Sweden
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Posted: Sat Oct 26, 2013 11:34 am Post subject:
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feggster wrote: | i think c13 is reversed on the layout compared to the schem. |
Damn, you're good! And right!
C13 was indeed the wrong way around.
Also, the BOM does not list R20, so I missed mounting that one too.
Now the filter works perfectly!
Only thing wrong is the positions on the switch. LP and AP is switched around, probably my mistake.
Thanks for the help! This filter is angry and very good sounding!
Now for som Erdinger weissbier!
Cheers
Sebastian |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Sat Oct 26, 2013 11:52 am Post subject:
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you forgot to install the resistor R20 (220K), the feedback resistor of the output amplifier. Therefore this stage behave as a comparator giving this horrid sound you have on your video.
EDIT: cross post, glad you find the error by yourself, the inversion of the polarity of the capacitor is without effect.
I will correct the BOM ASAP _________________ Yves |
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sebsongs
Joined: Feb 09, 2013 Posts: 49 Location: Malmö, Sweden
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Posted: Sat Oct 26, 2013 12:05 pm Post subject:
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yusynth wrote: |
EDIT: cross post, glad you find the error by yourself, the inversion of the polarity of the capacitor is without effect.
I will correct the BOM ASAP |
Cheers Yves! Thanks for spotting the mistake!
I think I have some more BOM updates for you on other modules. Will get back to you with those.
For now I'm very happy with the filter. It sounds so very different from the minimoog vcf. Opens up a whole new palette of sounds! |
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Benjamin AM
Joined: Nov 04, 2010 Posts: 83 Location: Boise
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Posted: Sun Oct 27, 2013 7:18 am Post subject:
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sebsongs
Any chance you could post a follow up video? I built this filter a few months back and would like to compare. My filter acts a little weird when in high resonance, also, I played a Minibrute and the filter seemed a little more "tame". I assume that this is just the nature of the filter bust I would like to compare.
Thanks |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Sun Oct 27, 2013 7:28 am Post subject:
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Which version did you build Benjamin ? The last one on my site is the same version as in the MiniBrute. _________________ Yves |
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Benjamin AM
Joined: Nov 04, 2010 Posts: 83 Location: Boise
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Posted: Sun Oct 27, 2013 7:48 am Post subject:
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I built the "Improved Steiner Filter" which I believe is the newest version. For clarification, I feel that the Minibrute's filter was the tame filter. The filter that I built sounds amazing but the resonance is a little quirky because it seems a little touchy even after adjusting some values. There is also some lag when adjusting the resonance knob, I didn't seem to notice this when playing the Minibrute. Possibly I need to do some more fine tuning. My PSU is +/- 15V. |
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sebsongs
Joined: Feb 09, 2013 Posts: 49 Location: Malmö, Sweden
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Posted: Sun Oct 27, 2013 9:08 am Post subject:
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Benjamin AM wrote: | sebsongs
Any chance you could post a follow up video? I built this filter a few months back and would like to compare. My filter acts a little weird when in high resonance, also, I played a Minibrute and the filter seemed a little more "tame". I assume that this is just the nature of the filter bust I would like to compare.
Thanks |
My filter is also a little unpredictable when resonance is turned up high.
I rather like that characteristic of the filter.
The range of my resonance is smaller than the turn of the potentiometer. It is tweakable by changing some resistors, I think.
I love how my yusynth modular can sound like a TB303 now with this filter. Really gritty and raw.
Can't wait to build the arp and ems filters and compare! |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Sun Oct 27, 2013 9:34 am Post subject:
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Benjamin AM wrote: | I built the "Improved Steiner Filter" which I believe is the newest version. For clarification, I feel that the Minibrute's filter was the tame filter. The filter that I built sounds amazing but the resonance is a little quirky because it seems a little touchy even after adjusting some values. There is also some lag when adjusting the resonance knob, I didn't seem to notice this when playing the Minibrute. Possibly I need to do some more fine tuning. My PSU is +/- 15V. |
If you have a lot of lag you reduce the value of C14 downto 1µF or even bypass it. _________________ Yves |
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Benjamin AM
Joined: Nov 04, 2010 Posts: 83 Location: Boise
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Posted: Sun Oct 27, 2013 10:58 am Post subject:
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Yves,
thank you for your help. While replacing the capacitor I noticed that I used a 100k pot for the cutoff knob! Needless to say, the true problem was that I was only getting about 65% of useful turn out of the potentiometer. Hopefully my mistake can prevent someone else some headache. |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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Posted: Wed Jul 30, 2014 9:47 am Post subject:
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yusynth wrote: |
EDIT: cross post, glad you find the error by yourself, the inversion of the polarity of the capacitor is without effect.
I will correct the BOM ASAP |
Hi Yves.
you still didnt correct it in your site for the new version
i did the same mistake following the pic _________________ http://www.myspace.com/mgmtrance |
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rhdf
Joined: Jul 11, 2014 Posts: 39 Location: Sweden
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Posted: Wed Jul 30, 2014 2:52 pm Post subject:
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yusynth wrote: | the inversion of the polarity of the capacitor is without effect.
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Hmm Does that mean you could use a non polarized cap there? |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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Posted: Wed Jul 30, 2014 3:01 pm Post subject:
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rhdf wrote: | yusynth wrote: | the inversion of the polarity of the capacitor is without effect.
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Hmm Does that mean you could use a non polarized cap there? |
to tell you the truth...i do feel there's a deference in the reso behavior after chaining the polarity of the cap. _________________ http://www.myspace.com/mgmtrance |
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rhdf
Joined: Jul 11, 2014 Posts: 39 Location: Sweden
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Posted: Wed Jul 30, 2014 3:14 pm Post subject:
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Quote: | .i do feel there's a deference |
To the better or the worse? (depending your preferences)
But what about a non polarized cap? |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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