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 Forum index » DIY Hardware and Software » Jürgen Haible designs
MatrixFX VCF
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Boerge



Joined: Sep 02, 2009
Posts: 73
Location: Germany

PostPosted: Mon Mar 19, 2018 2:49 am    Post subject: MatrixFX VCF Reply with quote  Mark this post and the followings unread

Hello @all,

has anybody tried to build Jürgens version of the VCS3 filter he used in his MatrixFX-Synth? He didn't publish the complete schematic, only his extension with a box saying "EMS LPF not disclosed". On a picture (matrix_fx_osc3_noise_filter.jpg) the complete schematic lies under the stripboard, and it looks like he built his circuit around the complete original circuit. Unfornately the pics are not available on Randomsources Website, the complete MatrixFX part gives a "403 - Forbidden" Sad
Does anybody know more or has tried to built this thing?

regards

Boerge


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LFLab



Joined: Dec 17, 2009
Posts: 491
Location: Rosmalen, Netherlands

PostPosted: Mon Mar 19, 2018 3:32 am    Post subject: Reply with quote  Mark this post and the followings unread

I recently did a board with an EMS-esque diode ladder VCF and a generic log VCA, used the schematics from Yves Usson's Yusynth site, he mentions that the schematics of the actual EMS VCS3 are not in the public domain. You could use the schematics found here: http://www.phutney.com/

This is mine:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Leftmost PCB, top and bottom:
Posted Image, might have been reduced in size. Click Image to view fullscreen.
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Boerge



Joined: Sep 02, 2009
Posts: 73
Location: Germany

PostPosted: Mon Mar 19, 2018 3:49 am    Post subject: Reply with quote  Mark this post and the followings unread

LFLab wrote:
... from Yves Usson's Yusynth site


That's where I got the schematics from too Wink But my interest goes more to the details of Jürgens circuit (LPF AND HPF), neccessary changes and so on...

regards

Boerge

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Eml



Joined: Mar 12, 2013
Posts: 1
Location: Belgium

PostPosted: Wed Jan 02, 2019 7:07 am    Post subject: Reply with quote  Mark this post and the followings unread

I made the EMS filter + Jürgens HPF adaptation many years ago. If you use the EMS schematic from the Yusunth page ( from his X-VCS3 page where he posted the original service manual) you will see that in Jürgens schematic, there is a small part of the EMS schematic (R84 and R85 and C32) what makes it very easy to put both schematics together. You don't have to make any extra adjustments. I also still have the mail from Jürgen where I asked him questions about it:
Quote:
>I would like to build your matrix FX filter. I think I understand how to
fit the original ems filter in your schematic, but to be sure, I've
adjusted the original schematic the way I think it should be. Can you please
take a look at it to verify I understood it correct?

Looks good, except that R84 and R85 and C32 are already in my drawing - you
only want them once.

>Also some of the NPN transistors are BC169C, and some are 2N5172. Can I
replace both by BC550C's? If not, can you >tell me the correct replacements?

BC550C and BC560C is what I use.

Can you also tell me what I can use to replace Q26 (2N5163 Jfet)?

I use a BF245. You should select it for a threshold voltage of ca. 4 ... 5
V.
Just _roughly_ that threshold. Then experiment with different values for R90
to get a good
response from the Resonance Potentiometer.

JH.



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Boerge



Joined: Sep 02, 2009
Posts: 73
Location: Germany

PostPosted: Wed Jan 02, 2019 11:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow, thats great! Help after so much time! Thanks for sharing your knowledge. Although I have (like probably all of us) always too many projects at the same time, my VCS3 has made some progress:

https://www.muffwiggler.com/forum/post-2853264.html&highlight=#2853264

Smile

Time to dig out the filter again...

regards

Boerge

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