[pcb+panel] ssm2044 filter for eurorack

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HipDestroyer
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Post by HipDestroyer » Wed Feb 03, 2016 4:39 pm


TimoRozendal
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Post by TimoRozendal » Wed Feb 03, 2016 4:55 pm

HipDestroyer wrote:What beads are recommended? Would these work?

http://www.reichelt.de/DFP-3-0/3/index. ... EARCH=bead

or this?

http://www.reichelt.de/BEAD-8-21/3/inde ... EARCH=bead
the first bead you link is not a correct one, the second one seems fine
it should look like this:
Image

I just bought a bunch on aliexpress

the beads are just for filtering the power supply, replacing them with 10R or 22R resistors should work fine as well..

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Post by jackmattson » Sat Feb 06, 2016 1:49 pm


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Post by TimoRozendal » Sat Feb 06, 2016 2:31 pm

jackmattson wrote:This works for the 180pf, right?
http://www.mouser.de/ProductDetail/EPCO ... 652A2181J/
I don't think there is a 180pF in the bom (are you sure you are using the correct bom now?), there is however a 820 pF and for that one the spacing should be much less than the 15mm one you've shown, it should be 5mm
(it is meant for this size 7.2x4.5x6mm, though others might fit as well, perhaps by placing them on the back of the pcb)

I have bought a bunch of these and I can send you one for shipping costs if you want

Image
Last edited by TimoRozendal on Sat Feb 06, 2016 2:46 pm, edited 2 times in total.

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jackmattson
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Post by jackmattson » Sat Feb 06, 2016 2:35 pm

Shit wrong BOM. I'm having issues sourcing the 820pf

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Post by TimoRozendal » Sat Feb 06, 2016 2:39 pm

jackmattson wrote:Shit wrong BOM. I'm having issues sourcing the 820pf
yes, that is what I was talking about, I can help you with that
(but also mentioned the wrong value before the edit)

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ehafh
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Post by ehafh » Sun Feb 07, 2016 6:58 pm

i built this today and made a quick video demo.

[video][/video]

:nana:

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Post by TimoRozendal » Mon Feb 08, 2016 3:20 am

ehafh wrote:i built this today and made a quick video demo.
:nana:

awesome! :yay:

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Post by antf4rm » Sat Feb 20, 2016 2:39 am

jackmattson wrote:I would have been but I was missing a couple of caps.
BTW at work and making a mouser order (not infront of my PCB) but the pdf only lists 2 Pots and there are 4 on the panel.

Are the other (not P1 and P2) pots also B50k? One is for gain so I would assume that it's AX0k.
Looking here... http://modular.fonik.de/pdf/SSM2044small.pdf

Another question... I ALWAYS get the wrong size trimmers. Do you have part numbers or some key word to search for so I get the ones that fit the holes? (multi turn or single turn)?
I picked up these for this project. They are nice!

http://www.mouser.com/ProductDetail/Piher/PT6KV-203A2020/?qs=%2fha2pyFadujaWhHnTm3HyopamwtT2K5k%2f8cIw9siqbc7n0kRFQOvlg%3d%3d

http://www.mouser.com/ProductDetail/Pih ... 2fbg%3d%3d
Last edited by antf4rm on Sun Feb 21, 2016 12:46 am, edited 1 time in total.

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Post by antf4rm » Sun Feb 21, 2016 12:15 am

Finished the build today and all is well except i cant get the thing to self oscillate.

I've gone through the whole section of the circuit that feeds the q input of the sm2044. Everything is connected and the proper value.

I am getting some resonance just not enough for it to take off. Even with T3 cranked up.

When resonance and T3 are at max i'm only getting 1.7v at the q input of the chip. The data sheet says that it starts to oscillate when the input is 7.5v. hmm..

The only part that is not exactly to spec is the 820pf cap at C8. I've used a C0G there. Maybe that is the problem?

Edit: Found it........... I swapped C5 and C8 resonates like crazy now! :bang: and :bananaguitar:
Last edited by antf4rm on Sun Feb 21, 2016 3:55 am, edited 1 time in total.

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Post by TimoRozendal » Sun Feb 21, 2016 3:53 am

antf4rm wrote:Finished the build today and all is well except i cant get the thing to self oscillate.

I've gone through the whole section of the circuit that feeds the q input of the sm2044. Everything is connected and the proper value.

I am getting some resonance just not enough for it to take off. Even with T3 cranked up.

When resonance and T3 are at max i'm only getting 1.7v at the q input of the chip. The data sheet says that it starts to oscillate when the input is 7.5v. hmm..

The only part that is not exactly to spec is the 820pf cap at C8. I've used a C0G there. Maybe that is the problem?
Sorry to hear about your problems.
First off: I tested the chip you have in my own build and there it did self oscillate.
Things to check:
- does it self oscillate with the resonance knob to max AND 5v into the Q cv input?
- does the q trimpot make any difference?

Regarding the datasheet: they state a current where self oscillation occurs, the situation here is a different than the example they use because it is connected to an opamp directly, not via a 13k resistor, so the 7.5v at input pin is not the 'goal'

Having said that, I had the same issue in a build I made the other day and I simply increased R4 to 75k (I think I used that value, not sure)

I hope that helps, good luck!
Timo

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Post by antf4rm » Sun Feb 21, 2016 3:56 am

Found it man thanks!
I had switched C5 and C8 somehow :doh:

I didn't want to start putting more voltage into the q input of the chip. I was afraid i'd fry it. My intuition said look at the op amp circuit feeding the Q. So i didn't look elsewhere until i explained the schematic to my girlfriend and saw my mistake. It's nice to have a second person help you through your problems. :love:

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Post by antf4rm » Sun Feb 21, 2016 4:26 am

TimoRozendal wrote:
Having said that, I had the same issue in a build I made the other day and I simply increased R4 to 75k (I think I used that value, not sure)

I hope that helps, good luck!
Timo
I was about to try something like that to add some gain to the Q input. It would make sense seeing as this portion has not been modified for the 12v power.
Last edited by antf4rm on Sun Feb 21, 2016 8:37 pm, edited 1 time in total.

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Post by TimoRozendal » Sun Feb 21, 2016 8:33 am

nice antf4rm!
glad it works now :party:

in general there is no need to change this part of the circuit for 12v, because in most cases self resonance is easily reached (and going beyond that point is not so useful in my opinion)

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Post by HipDestroyer » Tue Feb 23, 2016 3:34 pm

Damn – I'm still missing a 820pf poly/mica. Anyone have a lead on it?

Otherwise really sweet and easy build so far.

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Post by TimoRozendal » Tue Feb 23, 2016 3:36 pm

HipDestroyer wrote:Damn – I'm still missing a 820pf poly/mica. Anyone have a lead on it?

Otherwise really sweet and easy build so far.
I can send you one if you like, PM me if you want that

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Post by jackmattson » Mon Mar 14, 2016 10:20 am

Can someone please add this (preferably also the wood one) to ModularGrid?

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Post by TimoRozendal » Mon Mar 14, 2016 11:09 am

jackmattson wrote:Can someone please add this (preferably also the wood one) to ModularGrid?
it's already there

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Post by jackmattson » Fri Mar 18, 2016 9:55 am

Finally built and sounds really cool! Nice clean resonance. Reminds me a little of a cross between the MA SVVCF and my Befaco BF-20 (Sallenkey ms20).

The resonance is as usual really dependent on the input volume. Gain can be over-driven to a nice harsh-ish clipping.

Somehow I can't find the tuning instructions.
Had a play and it seems the trimmer at the top controls the resonance/input gain. Found a nice spot where it shifts suddenly (when a saw is coming in at middle gain) and pulled it right behind that.
Bottom right seems to be cutoff bias or range. Turned Freq allt eh way down and turned that trimmer until the bass on our Gelenics just disappeared. Made sure I could open it all the way up and I still can.
Couldn't figure out what the bottom left trimmer did.

Edit:
Has a really nice liquid squirrelly resonance. No real formants other than the one peak. Makes a nice donk-like pop with my system x envelope. (When I touched somethign in the back I made a circuit that had some self FM buzzing in it. Going to try to recreate that and make a switch as a mod I think.) The way the cutoff modulates with with high resonance is really nice.
GREAT FILTER! :sb:

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Post by TimoRozendal » Sat Mar 19, 2016 6:40 am

jackmattson wrote: GREAT FILTER! :sb:
good to hear, thanks! :party:

the trimmers should function like this:
T1 sets frequency scaling (change this to get a better result with 1V/Oct signals)
T2 sets frequency offset
T3 sets resonance maximum

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Post by jackmattson » Sat Mar 19, 2016 11:00 am

Thanks! Btw, my FM attenuator is labled +- but never inverts the modulator. Is that expected, or did I mess up?

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Post by TimoRozendal » Sat Mar 19, 2016 11:37 am

jackmattson wrote:Thanks! Btw, my FM attenuator is labeled +- but never inverts the modulator. Is that expected, or did I mess up?
that is expected, it is an attenuator, not an attenuverter
though i must say I understand your point that you expected an attenuverter, but it was a design choice to place the + and - to show that they increase and decrease the influence of the line coming from the cv input

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Post by HipDestroyer » Sat Mar 19, 2016 3:50 pm

The fm input on this wonderful filter is so badass. I feel like Alice in adventureland whenever I plug an lfo into that bastard :yay:

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Post by oberkorn » Fri Mar 25, 2016 1:31 pm

HipDestroyer wrote:
Damn – I'm still missing a 820pf poly/mica. Anyone have a lead on it?
I can send you one if you like, PM me if you want that
same question here... though I put a ceramic one in there, works fine :tu:
don't know it it's supposed to sound better/different, but I put it in a socket so I can change later :)

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Need help troubleshooting (fake IC?)

Post by jhosef » Mon May 09, 2016 1:03 pm

I have a pretty good track record with my circuits - either from scratch or a bare PCB, but this has been a bit of trouble for me and I will admit defeat.

I guess that I should start by admitting that I started out on the wrong foot by connecting the front PCB a socket higher than the back board so it must have shorted something which promptly caused the bottom amp IC (nearest to the plug) to POP.

Also of note is that I had 2 SSM2044's that I got off of ebay awhile ago, not realizing the scourge of counterfeits. With no luck from these, I ordered one from UtSource.

After the initial snafu, I assembled the boards the correct way, confirmed that the voltages were correct at the IC sockets, changed out all the IC's to be safe and got nothing out of the filter. I did find that the bottom amp IC got really HOT with either of the SSM2044's that I had.

Suspecting a fake, I ordered from UTSource and now the bottom amp IC is cold, the SSM2044 gets warm in the center, but still nothing.

When I check the signal path with an oscilloscope, it gets through the top amp IC and promptly stops at the SSM2044.

Attached are images of both sides of the SSM2044 ICs that I have (UTSource one on the bottom) and the bottom PCB. My only deviation is that the 820pf is ceramic. I understand that this is no issue to it functioning, but I just got a poly one that I intend to swap at this evening.

The two board layout confuses me for troubleshooting, but what else might I have damaged connecting the boards wrong? Are there other points that I can check? I strongly suspect a fake SSM2044, but am looking for validation.

Thanks.

Image
Image
Last edited by jhosef on Fri May 13, 2016 2:07 pm, edited 4 times in total.

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