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 Forum index » DIY Hardware and Software » The layout factory
MS-20 (LM-13700 version),Polivoks or EMS VCF on veroboard?
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Sebo



Joined: Apr 27, 2007
Posts: 525
Location: Argentina

PostPosted: Sat Jan 05, 2013 5:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

AC mixer means that can only accept AC signals, in practice the coupling is done by a high pass filter with a sub sonic cutoff frequency, so in general an AC mixer is considered capable of mix audio signals but not CV signals. Also an AC mixer will kill any DC that try to come in.
A DC mixer is suitable for any signal, audio and CV, and it will pass any DC.

I'm not sure to understand your last question, but if you will always use that path, your VCA could be AC or DC, don't really matters.

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isak



Joined: Dec 13, 2009
Posts: 627
Location: Israel
Audio files: 18

PostPosted: Sun Jan 06, 2013 12:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Understud, thank you for that!
I'll build the mixer and let you and the guys know if it worked for the Jorg ms20.

cheers.

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isak



Joined: Dec 13, 2009
Posts: 627
Location: Israel
Audio files: 18

PostPosted: Wed Jan 09, 2013 4:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Sebo.

I build the mixer and added 10uF Tantalums to all inputs like you adviced me.
The + side to the input, the - side to the resistors.
It's sound better now Smile
You where right about the vol input!
I lower the vol input in the mixer and the square and saw sound much much better.

One thing is still bothering me, the self osc is comming to soon when turning the reso pot CW, is there any way to make it start in about 3 o'clock?

Thanks Sebo.
Isak E.

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Sebo



Joined: Apr 27, 2007
Posts: 525
Location: Argentina

PostPosted: Wed Jan 09, 2013 6:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi isak:
Great you get it sounding right!!!
I'm on vacation now, far away from home, I have to see the circuit to give you an answer. When I get back I'll check it out.
Cheers.

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isak



Joined: Dec 13, 2009
Posts: 627
Location: Israel
Audio files: 18

PostPosted: Wed Jan 09, 2013 8:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Sebo.

enjoy your vacation man.
See you soon Smile

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feggster



Joined: Sep 12, 2011
Posts: 50
Location: uk

PostPosted: Sat Jul 20, 2013 10:09 am    Post subject: Reply with quote  Mark this post and the followings unread

hiya,
I built this and it works great (a few modifications to the layout to get it working) now I would like to add a 3 way switch to change LP HP BP
I have a slide switch (shown below) can anyone translate the wiring diagram for my switch...my brain hurts
cheers.


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ms20lpbphp_switch.jpg
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gila_crisis



Joined: Feb 06, 2014
Posts: 3
Location: Switzerland

PostPosted: Thu Feb 06, 2014 3:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

I built a MS20 VCF following this schematic I found on takeda's site:
http://www.aleph.co.jp/~takeda/radio/MS20clone.html

But I have a problem. I used a TLC2272 and a OPA2134 for the dual opamp, transistors are BC560c and I'm powering the circuit with a MAX1044, so that I can get +/-9VDC out of a normal 9V power supply.
I double checked everything and the voltages on the IC seams to be correct but it doesn't work right.
After a while the circuit is powered the sound starts to come out and for a while it works, but after a bit I noticed that with the freq fully turned down, the filter slowly opens! I measured the voltage on the circuit and I found out that on the collector of Q1a (as per takeda's schematic) the voltage slowly arise with the time, resulting in this "self opening" of the filter. Do you have any suggestion what the cause may be?
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gila_crisis



Joined: Feb 06, 2014
Posts: 3
Location: Switzerland

PostPosted: Thu Feb 06, 2014 4:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

I found the mistake.. I just forgotten to connect pin2 of the opamp with the 470k resistor going to -15VDC!
Now it works like a charme! I'll post the layout soon.
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gila_crisis



Joined: Feb 06, 2014
Posts: 3
Location: Switzerland

PostPosted: Fri Feb 07, 2014 3:53 am    Post subject: Reply with quote  Mark this post and the followings unread

here you'll find my layout for Takeda's MS20 VCF. I added a charge pump to use it as a stompbox with a standard 9VDC power supplies (also with -/+9V instead of +/-15V the filter works really well! but you can omit the charge pump part of course).


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jmcecil



Joined: May 11, 2013
Posts: 20
Location: Prattville, AL

PostPosted: Sun Feb 23, 2014 4:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry to resurrect the oldie, but I'm trying to use protoboard for the first time and this seemed like a fairly easy project. I ran into an issue though. trying to read the diagrams on the first page I find a jumper coming off the -15 and I can't figure out what it is for. Can someone explain please?

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

Also, the schematics are no longer at the link on the initial post. Would anyone have a link?

Thanks much
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-minus-



Joined: Oct 26, 2008
Posts: 750

Audio files: 13

PostPosted: Mon Feb 24, 2014 3:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'd say that cut to the left of your long rectangle should not be there. If you have already cut this board, you will need to bridge that gap. You could use a piece of resistor leg and solder to the reverse side. Or you could swap R6 and the jumper, then bridge the gap with a three hole horizontal jumper to take the (-)V to pin 11 of the TL074.
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jmcecil



Joined: May 11, 2013
Posts: 20
Location: Prattville, AL

PostPosted: Mon Feb 24, 2014 6:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

-minus- wrote:
I'd say that cut to the left of your long rectangle should not be there. If you have already cut this board, you will need to bridge that gap. You could use a piece of resistor leg and solder to the reverse side. Or you could swap R6 and the jumper, then bridge the gap with a three hole horizontal jumper to take the (-)V to pin 11 of the TL074.

hey thanks, that actually makes sense. It's odd because that is the graphic from page 1. If it obviously that wrong, I'm surprised I don't see anyone pointing it out.
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roglok



Joined: Aug 28, 2010
Posts: 156
Location: uptown

PostPosted: Tue Feb 25, 2014 1:38 am    Post subject: Reply with quote  Mark this post and the followings unread

jmcecil wrote:
-minus- wrote:
I'd say that cut to the left of your long rectangle should not be there. If you have already cut this board, you will need to bridge that gap. You could use a piece of resistor leg and solder to the reverse side. Or you could swap R6 and the jumper, then bridge the gap with a three hole horizontal jumper to take the (-)V to pin 11 of the TL074.

hey thanks, that actually makes sense. It's odd because that is the graphic from page 1. If it obviously that wrong, I'm surprised I don't see anyone pointing it out.


pointed out here already:
http://electro-music.com/forum/post-341471.html#341471

cheers!
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jmcecil



Joined: May 11, 2013
Posts: 20
Location: Prattville, AL

PostPosted: Wed Feb 26, 2014 5:27 am    Post subject: Reply with quote  Mark this post and the followings unread

roglok wrote:
jmcecil wrote:
-minus- wrote:
I'd say that cut to the left of your long rectangle should not be there. If you have already cut this board, you will need to bridge that gap. You could use a piece of resistor leg and solder to the reverse side. Or you could swap R6 and the jumper, then bridge the gap with a three hole horizontal jumper to take the (-)V to pin 11 of the TL074.

hey thanks, that actually makes sense. It's odd because that is the graphic from page 1. If it obviously that wrong, I'm surprised I don't see anyone pointing it out.


pointed out here already:
http://electro-music.com/forum/post-341471.html#341471

cheers!

crap, right under my nose. Thank you!
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