TubeOhm SMR4P-multi Eurorack filter

Apologies if this has already been mentioned, but this caught my eye:

I’m a great fan of André’s transistor ladder and Steiner-Parker filters for the Shruthi, as well as the Shruthi SMR4 filter. I’ll be ordering and building one of these.

I’d also encourage André to do a eurorack version of his Steiner-Parker design for the Shruthi, which uniquely tamed the out-of-control resonance characteristics of this design, without losing its character.


Hey! Originally i just wanted to open a thread with my impression for the filter… but since your post has already the perfect name i just will add my impressions here.

May i already say: If you think about buying it: Buy it! It is worth every cent and for all its features it is quite cheap i think.

To the building:
I was the “beta-tester” of the very detailed building instructions, Andre made.
The instructions are very very detailed and every step is explained.
But anyway: the building is sophisticated and definitly only something for someone who is well experienced in soldering!

The sound:
At first i didnt understood the symbol on the frontplate. The razorblade.
But after listening to it, the icon makes sense. The sound is very clear and original. It is a good filter to get rid of frequencies without changing the original charakter. …well if you want it that way.
The resonance first let me think i made a mistake while building, but sometimes it is indeed a feature and not a bug.
The resonance is at its “peak” about at 2/3 of the position, the last third is going into boost.
And what an boost that is.
In “usual” circumstances i went at most to half of the possible resonance.
What i really love is the FM! It strongly depends on what signal you put in the filter… But with that feature you can give a bit charakter to your sound.
And of course: 15 Filter types!! What comes in really handy: you can change the types over cv!
With some signals there is a pop noise when changing on other signals you can change wildly without no problems. Definitly a damn nice feature to just plug some lfo or other random signal in and see what happens.
Also a nice thing which at first i underestimated:
The build in vca: Very nice and clean sound, closing completly.

The quality of the module is very decent and the look is also very nice.

I have to admit it is only the 4th filter module i own/used. But it definitly is my favorite “tool” in my rack so far! And for that price it is a bargain!

And yes… it is a bit of an “advertisment”. :wink:
But i am really happy with that filter and i definitly want to support Tubeohm to help him creating more nice modules in future! :slight_smile:

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I noticed this appearing on Thonk the other day.

Thanks for the review, @derkollo. I’m interested to know what makes the build challenging.


It is not challenging in terms of “tricky parts”, but just because there are a lot of parts to solder and the module is made of 3 pcbs. So troubleshooting can be tricky. :wink:

Hi Benne - next - and some other things also …

Mmm… Tempting! Im a sucker for filters and this sure has some unique features…

Excellent! I look forward to the SP filter! I’ll order an SMR4P filter today (from Thonk, I need some other things from them).

Lovely filter!

Couldn’t resist changing the LED colours a little :slight_smile:
For the LP and HP filters at least green indicates gentle filtering, and redder colours signify increasingly stronger filtering.

The orange LED needs a 1k resistor (R6), the red one a 220R one (R5), to get matching luminosities.


Looks like a pretty well featured filter! Much more advanced than many filters that you can get for eurorack, and it being SMR4-based makes it even cooler. Too bad I’m out of DIY for a white…

When you say you’re “out of DIY”, do you mean you’re not designing panels for DIY projects any more, either?


No just that I don’t have any time for DIY atm, or better, when it comes to having to choose I’ll chose making some music over DIY, since my time is a bit limited as of lately.
But I still make panels for DIY projects, recently did a new run of Neron panels for Magpie for example and I’m always open to helping people who develop kits.

Hi Derkollo, I just build a SMR4P but I need some help would you be willing to help me?

Hi, i sure can try to help. What seems to be the problem?

Well I finished the build which had super detailed pictures and info.
But when I powerup I only get the first led to light up and the fades in like 5 seconds.
I tested voltsges of the analog board and everything seems good.
the problem comes when I attach the control board.
The voltages dont add up and the fuse on the analog board gets super hot.

I’ve just received a ready-built one from Matttech in Manchester, UK. I believe that he has a few in stock. I will be having a play with it tonight . . .

Sounds like something is draining a lot of power on the control board. It is always hard to diagnose a diy-build over text… You say you tested all voltages on the analog board and all are good? Did you doublecheck all devices which are polarized like the capacitors, and all ICs? Are there all put in the right direction? On the controlboard the same: Everything in in the right direction? Any shorts on the solderside? You mentioned the voltages doesnt end up. Which ones in specific? Is it possible for you to post good quality picture of the boards from both sides?

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Hey man, thank you so much for your help, I had installed one IC in the wrong direction. Already ordered another piece. Thank you!

You are welcome. I am glad i was able to help with so little effort. :smiley:

André can you hear that`?