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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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hoyager



Joined: Feb 16, 2010
Posts: 27
Location: New Zealand

PostPosted: Sun Oct 30, 2011 5:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

You can get high pass by pulling the grounded end of C4 (1n) up, using that end as the input.
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LektroiD



Joined: Aug 23, 2008
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PostPosted: Sun Nov 13, 2011 11:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

citric acid wrote:
Clack wrote:
Hey thats good! no problem. Wow big caps!

Looking at it the LED's are a bit close aren't they!

I will update the layout , how does it sound?

-Ben


hi ben,

have you an updated version ?
that will be verry nice.

thanks,
cit


Indeed, a final version would be cool. I'll hold off building until that comes around. Thanks for putting this project together though, looks great.
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synthesist



Joined: Feb 17, 2011
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Location: austria
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PostPosted: Mon Nov 14, 2011 7:48 am    Post subject: Reply with quote  Mark this post and the followings unread

I read somewhere that the original ms20 filter works in a way, that the signal goes through the highpass first before it passes the lowpass filter?

Is it true, or do I remember wrong? If yes, I would like to give this a try.
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remork



Joined: Aug 02, 2009
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PostPosted: Thu Nov 24, 2011 11:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

yup, HP first, then into LP.
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synthesist



Joined: Feb 17, 2011
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PostPosted: Tue Mar 13, 2012 2:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well it is a few months ago now that I build the filter but there is one thing that is bugging me. If I drive 2 soundsources into the VCF I have to be very carefull not to turn on the volumes of the incoming sounds too loud or the VCF just switches off Shocked
Same thing happens if I pump too high control voltages into it, but then it only happens if I open the cutoff frequencie knob all the way up.
Pretty annoying because it is hard for me to know when it is too much.

Do you guys think this is "normal" or can I avoid this somehow?
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isak



Joined: Dec 13, 2009
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PostPosted: Sun Mar 18, 2012 12:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Guys.

This looks like a very cool project.
Can anyone tell me what is the range of the filter?
Is it full range 20Hz to 20Khz?

Cheers,
Isak E.

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mrkva



Joined: Jan 25, 2012
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PostPosted: Mon Mar 19, 2012 2:54 am    Post subject: Reply with quote  Mark this post and the followings unread

+1 for the updated version. anyone? Rolling Eyes
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hoyager



Joined: Feb 16, 2010
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PostPosted: Mon Mar 19, 2012 11:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

synthesist wrote:
Well it is a few months ago now that I build the filter but there is one thing that is bugging me. If I drive 2 soundsources into the VCF I have to be very carefull not to turn on the volumes of the incoming sounds too loud or the VCF just switches off Shocked
Same thing happens if I pump too high control voltages into it, but then it only happens if I open the cutoff frequencie knob all the way up.
Pretty annoying because it is hard for me to know when it is too much.

Do you guys think this is "normal" or can I avoid this somehow?


I have the same with the one I've built, the psu is fine.. happens with lots of res gain as well, if the signal is hot.

Could attenuate the input, but then the self res will be too loud, and the 'output buffer'? would need some more gain, or another gain stage to follow, I'm guessing.

Does anyone else know why this would be happening?

Andy
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robboten



Joined: Nov 26, 2009
Posts: 35
Location: stockholm, sweden

PostPosted: Sat Nov 17, 2012 12:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Anyone have a PCB layout for the Rene MS-20 with 13700?
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oculus



Joined: Oct 30, 2011
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Location: Iceland, Reykjavik

PostPosted: Wed Nov 28, 2012 2:22 am    Post subject: Reply with quote  Mark this post and the followings unread

i just breadborded just by going after the schematic on René Schmitz page.
im finding the resonance way to much with the 1n cap which is located near the led´s(diodes) i tried put 220 pf ceramic and it´s seems to be nicer the resonance knob doesn´t scream as suddenly now.

btw im using 12Volt , resonance knob 100k and cutoff 47k
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isak



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PostPosted: Wed Nov 28, 2012 3:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the info.
The 1n you reffering to is the one from the left in the schematics?

Cheers,
Isak E.

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oculus



Joined: Oct 30, 2011
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PostPosted: Wed Nov 28, 2012 11:00 am    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
Thanks for the info.
The 1n you reffering to is the one from the left in the schematics?

Cheers,
Isak E.




yes thats right, maybe you should try 2n cap also. i noticed that they used 2n in the original schematic i saw somewhere
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isak



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PostPosted: Wed Nov 28, 2012 12:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

2n you say...mmm...
Where did you saw that?

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oculus



Joined: Oct 30, 2011
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Location: Iceland, Reykjavik

PostPosted: Fri Nov 30, 2012 9:24 am    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
2n you say...mmm...
Where did you saw that?


here´s a intensive info about the ms filters - http://www.timstinchcombe.co.uk/synth/MS20_study.pdf

if you scroll down a bit you will find a schematic containing a lm13600
and there they use 2.2n
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isak



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PostPosted: Wed Jan 02, 2013 9:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi oculus.

i put 2.2nF, it made the reso much stronger and unstable, screems like hell, the peak level is very high/distorted.
tryied with 220pF, the reso was to weak.
actually the 1nF was the best chice but yet again...not perfect.
i didnt do the stripboard version, i did the Jorg Schmitz one.
http://www.analog-synth.de/synths/mod2/ms20filter/rene_ms20_filter_clone%20rev%204.pdf

you can hear sound demos in the next link..
http://electro-music.com/forum/topic-56326.html

i'm not happy with the reso sound yet and hope i'll manage to fix it with the help of the members here.

cheers,
Isak E.

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Sebo



Joined: Apr 27, 2007
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PostPosted: Wed Jan 02, 2013 1:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi:
I built mine using the Schmitz PCB too.
The reso sounds OK, but is not exactly like the MS-20 reso, quite right but..
The original design uses 3 diodes in series instead the LEDs to limit the reso. I used green LEDs (colour is important), but I always wanted to try the diodes.
Also I built the One Board Farm monosynth from Motohiko Takeda that uses an MS-20 VCF clone based in the Haible schematic, and it sounds slightly better. The only difference I found is in the voltage divider in the input of the first OTA, and it used a LM13700 instead two CA3080.
Also the filter is very sensitive to input levels, is not adapted to modular levels, so at high input levels (10Vpp from a VCO without attenuation) the reso didn't self oscilate, lowering the level to half (5Vpp seems to correspond to the levels inside the MS-20) the reso works at it should.

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isak



Joined: Dec 13, 2009
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PostPosted: Wed Jan 02, 2013 2:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank for replying Sebo.

did you hear my sound demos?
Is it like yours?
I used 2 green LEDs as well.
What kind/type of diode in the original scheme?
actually the HP sounds really good, I love the HP very much.

Another problem I have ( I think it's related to the vco it self) the square don't sound good as the saw, the reso is not that strong, it's sounds like the vco is choking the reso for some reason.
Maybe it's related to what you said about the 10Vpp?
Any way the ody vco is not 10Vpp, it's 5 or 6Vpp with 12V power supply and 7 or 8Vpp with 15V power supply ( if I'm not mistaken).

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Sebo



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PostPosted: Thu Jan 03, 2013 7:04 am    Post subject: Reply with quote  Mark this post and the followings unread

The waveforms of the Odyssey VCO have a DC component, they aren't -2.5V to +2.5V, they are 0V to 5V (and 0V to 6V), I suspect that is causing you trouble.
ARP uses DC decoupling caps at the inputs of the VCF, you can do that or make a DC bias compensating circuit. I did a leveler and DC compensating circuit to get -5V to +5V out of the Odyssey VCO but I have to attenuate it to work right with this filter (I have attenuators in all my filters).

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isak



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PostPosted: Thu Jan 03, 2013 8:34 am    Post subject: Reply with quote  Mark this post and the followings unread

I will have all ody vco's going through this mixer...
http://yusynth.net/Modular/EN/MIXER/Mixer-2U.html
You think it would help?

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Sebo



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PostPosted: Thu Jan 03, 2013 3:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

No isn't helping as that mixer is DC capable, so no DC filtering.
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isak



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PostPosted: Thu Jan 03, 2013 10:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
ARP uses DC decoupling caps at the inputs of the VCF, you can do that

i missed that line..
how do i do that?

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Sebo



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PostPosted: Fri Jan 04, 2013 8:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Well... using a decoupling cap at the input of the MS-20 VCF is not that easy as I tought, as input impedance is lower than normal (because of the OTA). You can try conecting a 22uF cap in series with the input, I think It should work, but I'm not sure how this will afect the input impedance.

If you want to play safe, is better to decouple the mixer inputs as they are higher impedance, connect a 10uF cap between the wiper of the input pot and the input resistor (in every input you want to decouple).

The caps could be electrolitic but tantalum is better. The + leg of the cap should be connected to the input (where the signal input the circuit).

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isak



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PostPosted: Fri Jan 04, 2013 1:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok, I'll try that.
If do that won't i turn the mixer to AC mixer?

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Sebo



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PostPosted: Sat Jan 05, 2013 6:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, it will be an AC mixer.
You can use a switch to bypass the cap, and choose between AC or DC.

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isak



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PostPosted: Sat Jan 05, 2013 10:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Sebo.

Please explain to me when I will want to use AC mixer and when DC mixer?
I don't quite understand.
Another Q..
my chain is like follow, VCO's--->mixer--->VCF--->VCA.
if my mixer is AC what will be the VCA? AC or DC?

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