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 Forum index » DIY Hardware and Software » YuSynth
Steiner Parker filter weird behaviour. SOLVED!
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sebsongs



Joined: Feb 09, 2013
Posts: 47
Location: Kristianstad, Sweden

PostPosted: 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:
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.

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

PostPosted: Sat Oct 26, 2013 10:02 am    Post subject: Reply with quote  Mark this post and the followings unread

i think c13 is reversed on the layout compared to the schem.
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sebsongs



Joined: Feb 09, 2013
Posts: 47
Location: Kristianstad, Sweden

PostPosted: Sat Oct 26, 2013 11:34 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 1233
Location: France

PostPosted: Sat Oct 26, 2013 11:52 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Wink

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Yves
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sebsongs



Joined: Feb 09, 2013
Posts: 47
Location: Kristianstad, Sweden

PostPosted: Sat Oct 26, 2013 12:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

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 Wink


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: 70
Location: Boise

PostPosted: Sun Oct 27, 2013 7:18 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 1233
Location: France

PostPosted: Sun Oct 27, 2013 7:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Which version did you build Benjamin ? The last one on my site is the same version as in the MiniBrute.
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Yves
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Benjamin AM



Joined: Nov 04, 2010
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PostPosted: Sun Oct 27, 2013 7:48 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 47
Location: Kristianstad, Sweden

PostPosted: Sun Oct 27, 2013 9:08 am    Post subject: Reply with quote  Mark this post and the followings unread

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: 1233
Location: France

PostPosted: Sun Oct 27, 2013 9:34 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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Benjamin AM



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PostPosted: Sun Oct 27, 2013 10:58 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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PostPosted: Wed Jul 30, 2014 9:47 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Wink

Hi Yves.

you still didnt correct it in your site for the new version
i did the same mistake following the pic Laughing

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rhdf



Joined: Jul 11, 2014
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PostPosted: Wed Jul 30, 2014 2:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

yusynth wrote:
the inversion of the polarity of the capacitor is without effect.


Hmm Does that mean you could use a non polarized cap there?
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isak



Joined: Dec 13, 2009
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PostPosted: Wed Jul 30, 2014 3:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

rhdf wrote:
yusynth wrote:
the inversion of the polarity of the capacitor is without effect.


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.

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rhdf



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PostPosted: Wed Jul 30, 2014 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
.i do feel there's a deference

To the better or the worse? (depending your preferences) Wink

But what about a non polarized cap?
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isak



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PostPosted: Wed Jul 30, 2014 8:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

For better.

I didn't check a non polorized cap.

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