A Beginner in a Fonitronik SSM2044 VCF

fonik · Posted: Sun Jan 13, 2008 8:22 am Post subject:

how is it, oscar?

unfortunately i don't had the time to take a closer look at my modules for now.

nevertheless a suggestion: stay with the values for R17, R16, R11, R8 and T1 to keep the filter scalable for 1V/oct. lower the values for R9 to widen the response of the cutoff potentiometer (R23 is already lowered to 75k according to the latest documentation rev 3.2 from 25 Oct 2007)

http://www.modular.fonik.de/pdf/ssm2044_rev32.pdf

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

I'm here trying and trying.

If you change a component value it has effects at different points of the circuit.

According my measurements the filter at 15V can self oscillate 2hz to 20khz. The frequency potentiometer span response is eg 20hz to 5,5Khz or eg 40hz to 8Khz.

The filter at 12V can self oscillate 2hz to 20khz, but the frequency potentiometer span response is reduced to eg 20 hz to 1,6Khz or eg 40 to 3khz.

I'm trying, like you know, to increase the Frequency potentiometer response, but eg when I achieve it I lost the V/Octave control...

I'm thinking that the easy way would be to have a modular synthesizer with two power supplies...

But I would like to achieve a potentiometer frequency response about 20Hz to 10K. Very Happy

I will try your suggestion.

The filter is amazing. sounds very good. Yesterday I did a very good conga sound. Pulse to audio in. frequency a bit modulated by audio. Very Happy

.

EDIT: curiosity: would be possible to change R9 for a precision trimmer? If it is possible, would be necessary to ground the third leg?

Thanks.

prophei · Posted: Sun Jan 13, 2008 11:39 am Post subject:

i had issues with the cutoff range when i built my first version pcb. eventually i found that changing some values fixed the range rather well.

here was the discussion:

http://www.electro-music.com/forum/topic-17838.html&postorder=asc&highlight=ssm2044&start=50

...in case it might cover some stuff that this thread has not...

fonik · Posted: Sun Jan 13, 2008 12:52 pm Post subject:

i'd say bypass R15/R15' and lower the value of R9 as appropriate...

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Prophei,

thanks! But with your configuration is lost the V/Octave. And this is important to me.

Fonik,

If R9=100K and R15,15' = 0
I didn't achieve more span frequency potentiometer response. But the potentiometer only works 11h to 13h.

If R9=68K and R15,R15' = 47K
I didn't achieve more span frequency potentiometer response. But the potentiometer only works 9h to 15h.

Following the circuit you can see that all Frequency CV go to the SSM2044 "freq control" through R16.

So, (From the original circuit) I changed R16 to 120K. I achieved more span frequency potentiometer response but I lost the V/Octave!

I changed R11 to 220K. I recovered the V/Octave but! I lost span frequency potentiometer response. It is the same that at the beginning!

I have changed R9 to 68K and now yes! I achieved 20hz to 6Khz. If I go down more the value of R9 I don't achieve more frequency response.

That is a little bit more than if the filter worked at 15V. It is enough to me. Very Happy

But Maybe... Mr. Green

I will try to go down a little more R16 and R11 values in the way that it allow me to go down with R9 and R15 values for open the response of the potentiometer.

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

I have achieved it!

16hz to 16Khz!

R16=100K
R11=180K
R15,R15'=22k

Perfect V/octave.

If there isn't any mistake I will go to next step, solder the components to the PCB and while I will design and order the front panels.

One question: why the resistor R17 is mounted directly to the SSM2044?

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

fonik · Posted: Tue Jan 15, 2008 5:15 am Post subject:

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Hi.

I' m still Mr. Green

trying to choose knobs, colors, frontpanel design...

Well, for now I have chosen the way that I want to build them. I saw it in this interesting web side: http://homepage2.nifty.com/rjb/labo.htm the Japanese is a little dificult Mr. Green

to me but there are a lot of interesting pictures.

Anyone can tell me what is the name of the hexagonal piece that I marked in red. And where I can found it?

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Danno Gee Ray · Joined: Sep 25, 2005 Posts: 1351 Location: Telford, PA USA

Those are called standoffs. Available at Mouser, Digikey, etc.

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Thanks Danno,

I found it, but I'm designing now the front panel, and is a little dificult to place the standoofs without touch other components. I think that the other possibilty is put the PCB perpendicular to the front panel holding it with brackets. I'm looking on the net but i dind't found it.

Which brackets must I choose? where I can buy it? any reference number?

fonik · Posted: Tue Feb 19, 2008 7:03 am Post subject:

i just buy sheets of 0.5mm steel at the property market and cut them with plate shears, rasp and file the edges and drill it with my drill press. finaly i clamp it between to pieces of wood and bend it, improving the crook/angle using a hammer.
with a little practice you will be able to make your own cheap brackets within minutes...

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

fonik · Posted: Tue Feb 19, 2008 8:09 am Post subject:

i finaly settled with K Wink

fonik · Posted: Tue Feb 19, 2008 8:15 am Post subject:

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Tim Servo

fonik · Posted: Tue Feb 19, 2008 2:16 pm Post subject:

hello tim,

the first alpha potentiometers i ever bought were just these 12mm panel mount alpha potentiometers from mouser.
i know that there were some values not available in 12mm but 16mm package - but maybe that has changed meanwhile (don't know which value it was i did't find, but it was a common one...)

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

Hi guys,

If you see the attached front panel you can notice that I added an attenuated CV.

I would like to show you how I add an attenuated VC to the two filters Mr. Green

.

First I solded some components, after I remembered that I would add the CV, Scratch the PCB was more difficult but I did it. Also I have connected the cutoff positive and negative instead positive and ground. Also I forget to solder the decoupled capacitors before the IC sockets and it was more difficult after... but i did.

Maybe it would have been more easy to sold the wires at the PCB instead the put the sockets.

The filters are tested and they work perfectly! 16hz to 20Khz and 10V Pk-Pk, measured with my new Owon 5022 oscilloscope.

I'm very Glad waiting for the front panels. Very Happy

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

Sound · Joined: Jun 06, 2006 Posts: 842 Audio files: 1

A question, How I can do a better contact with the resistor 17 and the SSM 2044? I know that it is done with resine epoxi, but I don't like this material.

Is it possible with standard silicone or any kind of it?

Thaaaaaaaaaaaaaaaaaaaaaaaaaanks!

Tallhobbit · Joined: Aug 10, 2007 Posts: 15 Location: Kirkland, WA USA

For reworkable thermal contact, I use Arctic Silver 5. For a permanent thermal bond I use Arctic Silver thermal adhesive.

http://www.arcticsilver.com/products.htm

I prefer the adhesive and usually add a "service loop" to my tempco leads.

James

frijitz · Posted: Fri Feb 29, 2008 12:42 pm Post subject:

fonik · Posted: Fri Feb 29, 2008 2:58 pm Post subject:

ian, what could oscillate and where? how would this affect the tracking?
as you might know, i don't know much about circuit design and i am not that good in maths (i used to be in school, but that's ages ago Wink

), so plain words would be fine.