SMR4 & 4P filters upgrade

Hi all,
I’ve been building DIY stuff for my customers here in Japan and among them, of course, Ambika (renamed Pherkad).
Anyway, just wanted to let you know that I have slightly upgraded the SMR4 and 4P filters.
It is now possible to switch between 4-pole, 2-pole and 1 or 3-pole.
In the filter menu, only LP was active with those filters.
Now, BP and HP allow to switch between 2 more slopes.
BP= 1 or 3-pole (I have added a jumper on the PCB to select one of them)
HP= 2-pole
Here is what the SMR-4P (P for pole…) looks like:

I have no pictures of the 4P mk2 because I’m still waiting for the 1st batch of PCBs to arrive.

The upgraded filters can be installed in any standard Ambika/Tubika/Pherkad with no modification.
I can sell PCBs or prebuilt boards if interested.
For those who want to make their own PCBs, the Eagle files will be available for download soon.


That’s really cool!

Thanks, Olivier.
I am working on a multimode version of those filters too.
Also I made a stereo filter based on modified Dual SVF and Sidekick.
I call it Moka…


Looks cool.

I’m in Japan too. I’ve seen your stuff on Yahoo auctions before.
If you’re ever going to Five G in Harajuku, or Akizuki in Akihabara, and don’t mind someone tagging along, send me a PM.

Where can I find more info on that sidekick stereo filter?

How are the PCBs coming along for this? I am very interested.

I’ll start a thread about Moka.
But first, I have to work on some documentation and also work out the right license for it.
The problem is I work on it in my spare time (and I don’t have much) since those old MI projects don’t really pay the bills.
I keep them in my catalog and try to work on some upgrades but it is more for fun (and my love for them) than money.
And at the moment, I have other priorities that take almost all my time like the release of my brand’s 2nd eurorack module.


What PCBs are you talking about ?
Ambika’s or Moka’s ?

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Very short demo of the SMR4P switching between different slopes.
As a reminder, LP is the SMR4 standard 4-pole/24dB.
HP is a 2-pole/12dB slope and in this case, BP is a 1-pole/6dB slope.
Hope you’ll enjoy.
Prebuilt filters and PCBs are in stock if interested.
I will make available for download a ZIP on my website this week containing a BOM, schematics and Gerber files for those who want to make their own PCBs.

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No link to a ZIP file but Github repositories instead:


wow. Impressive. Any demo of the 4P?

Ambika’s. I was really interested in the upgraded 4P filter.

Did somebody test the 4p filters?

So, how much for the board? I’m interested in 6 of them.


i have 4 leftovers that i got printed :stuck_out_tongue:

I made a new version of those filters with the resonance point being switched as well.

Where/When can I purchase 6 of your awesome boards?

I must have these filters…

what are instructions for obtaining these

OK, guys.
Here it is.
I finished the multi-mode version of SMR4 and 4P filters.
Let you know my Github repository again:
SMR-4 Pi and 4P Pi are the new multi-slope versions of the filters.
SMR-4 Mu and 4P Mu are the multi-mode versions.
On the 4P Mu there’s one SMD part, a TL072.
Those are the final versions since I won’t work on them anymore.
At this point, the multi-mode filters are untested.
I should receive the 1st batch of PCBs in a few days and I’ll let you know if there is something wrong.
Until then, if you get some PCBs made, do it at your own risks.
Also, I’ll offer PCBs or pre-built boards soon.
Stay tuned…