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A Beginner in a Fonitronik SSM2044 VCF
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Sound



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PostPosted: Fri Jan 04, 2008 7:26 am    Post subject: A Beginner in a Fonitronik SSM2044 VCF Reply with quote  Mark this post and the followings unread

Hello,

I have already built 3 kits of Panther Synthacon Filter from Elby-designs . Basically, that is my DIY experience. Now I'm starting two SSM2044 filters from Mathias. I have only the PCB.

I'm publishing this post because to animate other people to start in DIY. It's complicated in the beginning but I think that in a few modules it will be more easy. It's very funny.

Of course, I'm also asking for any advice.

I will post the complete process of build it and the doubts which will be appearing .

Thanks,

Òscar.

Last edited by Sound on Fri Jan 04, 2008 7:46 am; edited 1 time in total
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Sound



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PostPosted: Fri Jan 04, 2008 7:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Well,

Yesterday afternoon, after I got all the components, I did my first breadboard. I tested the breadboarded circuit and It didn't work.

Today I have checked all the circuit and I have corrected some mistakes. I think that all is correct now but still it doesn't work.

One of the mistakes was that the ground was not connected.

Maybe I have damaged any component? what I can do? I have a multimeter: Can I measure anything in different points of the circuits?

Tomorrow I will upload a picture.

Thanks.
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ENDIF



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PostPosted: Fri Jan 04, 2008 12:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

You say you have only the board... does this mean you do not have the documentation for the project?

If not, it can be found here:
http://www.modular.fonik.de/pdf/ssm2044_rev31.pdf
http://www.modular.fonik.de/Page27.html

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PostPosted: Fri Jan 04, 2008 2:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

sound wrote:
Well,

Yesterday afternoon, after I got all the components, I did my first breadboard. I tested the breadboarded circuit and It didn't work.

Today I have checked all the circuit and I have corrected some mistakes. I think that all is correct now but still it doesn't work.

One of the mistakes was that the ground was not connected.

Maybe I have damaged any component? what I can do? I have a multimeter: Can I measure anything in different points of the circuits?

Tomorrow I will upload a picture.

Thanks.


Not connecting the ground probably did no harm. The filter not working, there can be many reasons. Mine didn't work the first time, I had stuck a resistor 100,000 times the required value Rolling Eyes in the audio in, essentially making no noise pass through.

Now is a good time to check all those resistor third band in - make sure they're right.

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fonik



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PostPosted: Fri Jan 04, 2008 4:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

i think it's a good idea to start with a breadboard and try a simple circuit. one can change components very easily and try different settings (especially if you want to optimize it for 12V Wink )

the first thing that comes to my mind is the following: did you check the pinout of the SSM2044 IC according to the datasheet? you should do. my schematic shows the IC without pin numbers, which is actually not good (it doesn't matter if use the PCB but on a breadboard it could be confusing, even misleading!): be sure to have pin 8 to GND and pin 9 to -V.
http://www.synthchips.com/ssm2044.pdf

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Sound



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PostPosted: Fri Jan 04, 2008 4:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Endif, Edison, fonik!

I have checked all the resistor values. They were OK.

About the SSM2044. I used this data sheet: http://www.maxmidi.com/diy/ssm/ssm2044.pdf . All seems correct.
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PostPosted: Fri Jan 04, 2008 5:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

More details.

Luckily, the SSM2044 can take a lot of grief. It's a pretty good chip.

One thing I found helpful is bypassing Fonik's buffer circuits, with a small resistor like 1k to the signal and seeing if you get noise. It might be you have more than one problem.

it would be best to eliminate the chip as a problem, so finding noise through it isn't a bad thing. There are ways to test this. The main way is to make the right control voltages happen at the right places, and a signal at the input, and look for the signal at the output.

I's not an exact science, but there are methods which work, if you are willing to be methodical.

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PostPosted: Sat Jan 05, 2008 7:04 am    Post subject: Reply with quote  Mark this post and the followings unread

EdisonRex wrote:
More details.

Luckily, the SSM2044 can take a lot of grief. It's a pretty good chip.

One thing I found helpful is bypassing Fonik's buffer circuits, with a small resistor like 1k to the signal and seeing if you get noise. It might be you have more than one problem.

it would be best to eliminate the chip as a problem, so finding noise through it isn't a bad thing. There are ways to test this. The main way is to make the right control voltages happen at the right places, and a signal at the input, and look for the signal at the output.

I's not an exact science, but there are methods which work, if you are willing to be methodical.


I 'll try to do it. ( if i have understood Mr. Green )

But... what is a buffer circuit?
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PostPosted: Sat Jan 05, 2008 7:15 am    Post subject: Reply with quote  Mark this post and the followings unread

This is my first breadboarded circuit: SSM 2044 fonik filter: Very Happy

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PostPosted: Sat Jan 05, 2008 7:39 am    Post subject: Reply with quote  Mark this post and the followings unread

from a first very quick review i'd say everythings seems to be okay. except the pot wiring: these are wired backwards. that would mean no input signal if P1 is fully clockwise, or low cutoff frequency when P2 is fully clockwise (leading to no output signal).
if you take a look at my documentation: the red wire (edit: the red one according to my documentation, not your breadboard!) would go from P1 to GND, the yellow would come from the input socket...

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Sound



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PostPosted: Sat Jan 05, 2008 4:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very Happy

It is working!

First I well wired the potentiometers.

After I started to play bypassing the audio signal and measuring the voltage at different points of the circuit...

I noticed that taking -12v to different points of the ground I got different voltage values.

The mistake was that I thought that the buses of the breadboard had two channels but! they have two groups of two channels. So I have connected them and it works.

http://farm3.static.flickr.com/2341/2169505703_f47d1d1d22_b.jpg

So I'm in the second step Mr. Green "setting up the filter"

All seems Ok except the cutoff potentiometer , I chosen the "alternate wiring for wider range " but when the cutoff knob is at 7h to 9h it not responds at the CV cutoff and the frequency range end when the knob is at 2h to 5h.

I have to add that I'm working with 12V because I have only one power supply.

Do you think that I must check this circuit first at 15v?

Any advice?

( I want to optimize the filter for 12V)
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PostPosted: Sun Jan 06, 2008 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

sound wrote:
It is working!

congrats! Very Happy

that's what i do in case a (proven) module does not work as expected: first i try to locate the problem by thinking about it. where could it probably come from? (often this is a little bit hard to do. the more complex a circuitry the more the parts of the circuit may interact and depend on each other.)
then i start to "greenline" the circuit (or the suspicious parts): i use the multimeter to check all connections and color the verified parts in green on the schematic.
then i start to verify the components and/or values.
ray wilson provides this little troubleshoot guide:
http://www.musicfromouterspace.com/analogsynth/troubleshoot.html

Quote:
So I'm in the second step Mr. Green "setting up the filter"

All seems Ok except the cutoff potentiometer , I chosen the "alternate wiring for wider range " but when the cutoff knob is at 7h to 9h it not responds at the CV cutoff and the frequency range end when the knob is at 2h to 5h.

the 47k for the resistor to GND from P2 (cutoff) provides a sub audio range, thus you could use the filter as LFO in selfoscillation. remember, you could use this filter as sin osc, therefore the 1V/oct trimmer...
adjust the init range using trimmer T2 until you are satisfied with the 2h to 5h range of the potentiometer.
(or even experiment with different values for the 47k resistors around P2. this would give you a feeling for that - a major advantage of breadboards)


Quote:
I have to add that I'm working with 12V because I have only one power supply.
Do you think that I must check this circuit first at 15v?

no. it works well with 12V.

you may want to reduce R23 to a lower value than 100k to have a more sensitive CV2 in (it is attenuated anyway).

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PostPosted: Mon Jan 07, 2008 10:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi! Thanks for the link and advice!

There was another mistake in the bread boarded circuit. The 100k cutoff resistor was bypassed.

Now the cutoff range is from 30hz to 3Khz. 7h to 5h. I don’t achieve go more far than 3Khz. Do you?

I think that set up the filter is a difficult thing for a beginner. Because we don't know which steps follow and also because we don’t know how the filter response is when it is set up.

So, what response can I hope from this filter? What I need to achieve with the set up of the filter?







(Before change any value component (I’m losing my self! Mr. Green ) I would set up the original filter circuit)
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PostPosted: Tue Jan 08, 2008 6:38 am    Post subject: Reply with quote  Mark this post and the followings unread

The Fc voltage control can be thought of as a voltage divider, and ranges nominally from almost -V to almost +V. Those resistors between +V, -V and the potentiometer are limiting the range of the pot. Because you're running at +-12V instead of +-15V, you might try smaller resistors like 33k instead of 47k.
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fonik



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PostPosted: Tue Jan 08, 2008 7:05 am    Post subject: Reply with quote  Mark this post and the followings unread

did you try T2 yet?

T2 is a kind of overall cutoff potentiometer allowing you to raise or lower the range of the whole CV circuitry (it will not widen it, but just move it up or down).

set the cutoff potentiometer to fully clockwise. then turn the trimmer to raise the overall cutoff frequency until you hear no change of cutoff. stop turning the trimmer just when reaching that point.

if you are not able to reach that point, proceed as mentioned by EdisonRex. you can change the values of these limiting resistors anyway, to achieve a wider range from the potentiometer (if desired). you can add a fine tune potentiometer, too (just another cutoff potentiometer but with 300k for R9...

i wonder how low one could go with the frequency before the filter stops to oscillate? never tried this.

since you have the filter on the breadboard just experiment with some values.

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PostPosted: Tue Jan 08, 2008 7:36 am    Post subject: Reply with quote  Mark this post and the followings unread

when this filter has its cutoff at fully clockwise, does it pass audio through exactly as it came through? in other words, is cutoff at 100% equal to bypass? (so a 25khz tone would come out at 25khz?)

thanks

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PostPosted: Tue Jan 08, 2008 1:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
(so a 25khz tone would come out at 25khz?)


This will happen always as a filter does not change the frequency of a signal going through it. It will amplify or attenuate signals depending on what frequency they happen to have (and the filter settings / properties of course).

When you have a low pass filter which is set to let's say 20 kHz everything well below that 20 kHz will be passed on unchanged, signals around 20 kHz and above will get changed in amplitude. Depending on the Q factor (resonance) signals around 20 kHz might be amplified or attenuation might start to kick in, signals well above 20 kHz will be attenuated.

With the example above and my ears a signal would pass through it unchanged, a dog might think different about that.

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Sound



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PostPosted: Wed Jan 09, 2008 9:05 am    Post subject: Reply with quote  Mark this post and the followings unread

I have noticed two different concepts:

1) The wide range that the filter covers: It coincides with the wide range that the filter can self oscillate. I have test it passing white noise flat equalized through the filter. When the filter stops to self oscillate the filter stops to affect the signal. I have achieved 2hz to 3khz (6Khz bypassing R18,R9)

2) The wide range that cover the frequency potentiometer.

Edison, I have tested different values in those resistors (R15, R15’) included bypassing them and I don’t achieve to extend the wide range nor extend the wide response of the Frequency potentiometer.
I have achieved arrive to 6 KHz only bypassing both resistors R18 and R9.
Also I was testing the filter with 15V with same results.

Quote:
did you try T2 yet?

Fonik, Yes I am playing with T2, R18, Frequency potentiometer, R15 and R15’

Quote:
to achieve a wider range from the potentiometer (if desired). you can add a fine tune potentiometer, too (just another cutoff potentiometer but with 300k for R9...

I’m trying it without results. I will try more in this direction.

Quote:
I wonder how low one could go with the frequency before the filter stops to oscillate? never tried this.

I achieve arrive to the low end of the filter changing R18 to 100K.
The filter stops to oscillate about 1, 6 Hz (manual timed).
The audio that I have upload is a signal modulated by the most low frequency that I have achieved. I have tried a lot of possibilities.

Quote:
since you have the filter on the breadboard just experiment with some values.

Yes, if any one of you want that I test something I can do it also.

I have a question for all you: what range has your ssm2044 filter?



I am measuring it (audio range) with the free plugin voxengoSPAN http://www.voxengo.com/product/SPAN/


V.wav
 Description:
Audio signal modulated by lowest signal self oscillate from 2044Fonik filter.

Download
 Filename:  V.wav
 Filesize:  969.61 KB
 Downloaded:  496 Time(s)

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Sound



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PostPosted: Wed Jan 09, 2008 3:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

!

I tried to change the PT146 R17 for a standard 1k resistor and the filter extends the range to 2hz > 18Khz!!!! (approximate measures)

Why? Shocked

After, I have noticed that R17 affects at the wide range of the frequency potentiometer. I have found that with R17= 2K the potentiometer cover approximate all the range of the filter.

Very Happy
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PostPosted: Thu Jan 10, 2008 1:37 am    Post subject: Reply with quote  Mark this post and the followings unread

sound wrote:
I tried to change the PT146 R17 for a standard 1k resistor and the filter extends the range to 2hz > 18Khz!!!! (approximate measures)
Why? Shocked

Question Question Question

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PostPosted: Thu Jan 10, 2008 2:34 am    Post subject: Reply with quote  Mark this post and the followings unread

i don't get it.
you will get a different response when changing the ratio of R16/R17. if i am not mistaken they works as a voltage divider, so that is clear to me, BUT i don't understand the difference between 1k standard and 1k PT146.

i even don't understand, that bypassing the limiting resistors R15/R15' won't affect the range of the potentiometer. there must be something wrong!?

i hope i will have some time on the weekend to do some measurements on mine...

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PostPosted: Thu Jan 10, 2008 2:52 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:


i even don't understand, that bypassing the limiting resistors R15/R15' won't affect the range of the potentiometer. there must be something wrong!?



Hi fonik. R17 with standard resistor, If I bypass the R15/R15', yes, it affects the range of the potentiometer.

The thing is that with the 1K PT146 the filter stops to selfoscillate at 3Khz. (6Khz bypassing R18,R9)

I don't understand.

I'll recheck all the breadboarded circuit.





Many thanks all you.
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PostPosted: Thu Jan 10, 2008 2:56 am    Post subject: Reply with quote  Mark this post and the followings unread

so everything is as supposed to, as long as you (edit) use a standard 1K instead of the PT146? did you measure the actual resistance of the PT146?
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Last edited by fonik on Thu Jan 10, 2008 4:00 am; edited 2 times in total
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PostPosted: Thu Jan 10, 2008 3:05 am    Post subject: Reply with quote  Mark this post and the followings unread

The PT146 value is 1K.

Also with the multimeter
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PostPosted: Thu Jan 10, 2008 3:58 am    Post subject: Reply with quote  Mark this post and the followings unread

i am puzzled...
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