SMR mkII v0.3

I made at pcbway this shruthi filter v0.3. Then i heard there was an issue with the board? is this true? didnt finish building it. The board without the LT on.

Yes…i found the topic…
Well is there anything i can do about it? asside from take it apart.

This file? Shruthi-Analog-SMR4-mkII-12V-v03

Why did you make it? I have never published any BOM or documentation about it. It has never been put in production because it’s a bit too noisy.

@pichenettes Yeah. i made the pcb. Extracted the bom from eagle. Build a lot of your stuff diy, eurorack too. I thought: "ohh look v.3 that looks fun. i better build it :)))"
Will better take it apart :)) couldnt wait to power my xt. and than baam i heard about this.

Gosh, I made the same mistake, I have seen “V0.3” and concluded “cool, this is the latest version”
SHould I simpky thrash the boards and take the components apart?

In no circumstances you should trash boards (unless you’re talking about a dedicated garbage bin for electronic trash).

If you’ve fully built the board, you can give it a try and check if you like it. Maybe you’ll like the sound of those Darlington buffers :slight_smile: The noise floor is not good, though…

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yes, I have a board fully populated and some other partially (80-90% populated)
And, no, I don’t have a dedicated bin for fucked-up boards :wink:
My problem is that the first board I have tested doesn’t even power up the shruthi
(I was able to flash the atmega on the digital board)
If you say that it should be working I might check it in a better way…but the tutorial page is for v02 only…well I guess the voltages on the various IC should be the same…

Not at all. Notice the “12V” in the name of the board? It’s designed to run with a 12V PSU (down-regulated to 9V), and a single-supply for the analog section. So you’ll read 9V where you should read 5V, 0V where you should read -5V, and +5V at various points that are grounded in the normal version.

ok, thanks for this explanation, really useful.
The board doesn’t seem to even power up the shruthi…
I might start checking for 9V and 5V in the power section…i can follow the Eagle files and schematics…
I expect the voltages that go to the “digital” section are the same, am I right? (Only + 5V should go to the digital, correct?)

Finger crossed (I really don’ want to desolder hundreds and hundreds of components)

Yes, the digital board is still supposed to get its +5V from this filter board!

well, some progress here…I checked and all voltages on the SMR4 seem OK. I can now power on the Shruthi (the headers between the two board weern’t simply having good contacts)

Let’s now try to program it and make it work (so far the display is all blue but nothing on screen). I am able to program, but nothing else works (only the last led lights up, no button work…)

OK…seems to be mostly working now, the LCD trimmer had a bit of a cold joint and wasn’t working properly :wink:

(BTW: thanks I see you have added a huge “DO NOT BUILD” on the .brd file :wink: )

OK, the shruthi is working even with the “odd” 12V board. I have just one issue…the resonance is very high on most of the patches (it gets self-oscillating even after releasing a key)…If I turn Resonance under +/-20 , it is normal, but after 20 it gets screaming and scra
eming…and stays on even after no key is pressed…
I need to ower the self-oscillating point…
I have seens some comments here (Can hear resonance after releasing note SMR-4 mk1) and @pichenettes suggested a 1M or 2M between legs of IC4…but it was MK1…iC4 seems to b ethe TL074 on MK1 and MK2, am I right?

No you’re mixing things up. The post you link to is about VCA bleed, it’s not about resonance.

What you need to adjust here is the value of R39 and R40. Try doubling both.

Thanks a lot Emilie!!!
I had a couple of 30K resistors lying around and I replaced both R39 and R40 with them. The high resonance is now gone :wink: