Swap vintage filters with the MI ones

Hi !

I’ve checked the discussions and didn’t find an answer…

I love filters, I got a shruthi 4PM a few months ago and it becomes my fav synth. Wandering on youtube, I found a demo of a shruthi with IR3109

My questions :

Is it possible to swap the MI filter with non MI filters ? Do I need a special board ? I dare not open my baby to see - if it doesn’t work after I would be desperate ! :slight_smile:

Sorry if I sound like a newbie (I’m one indeed !) I’m used with hardware like the Pulse or the jd800 but not with diy synths…

Thanks for your answers…

There used to be a series of MI filter boards with vintage filter chips. But they were phased out, the main reason being that the chips they used are of importance to owners of very classic synthesizers and having DIYers use up all the spares isn’t a nice thing to do.

Also, chips are limited in what they can do, discrete lets you do anything.

Thanx for these infos ! The IR3109 can be found on boss pedals too…

So it needs a special board… Pity… :frowning:

Shiftr told me the smr 2 sounds close to the Roland filter, so maybe I should go for it…

You don’t swap filters but filter boards. That’s the entire board at the bottom of your Shruthi. It contains all the circuits required for the filter to operate. You cannot transform your Shruthi just by swapping a single component.

But don’t bother with the IR3109, it has nothing special inside (it’s just a quad OTA and exponential converters, you can do exactly the same thing with 2 LM13700s and a few op-amps).

Hi Ercole,
nice to see a new thread.
It’s even nicer just to have another shruthi with another filter then to swap the filter boards out.
Tubeohm sels the kits now in the EU
Laurentide synthworks in the US

There are also a few threads on the forum on how to let the SMR sound even more like the Roland IR3109.
Tubeohm also sells his own very nice Moog ladder filter and a new stereo filter.
Tubeohm also sells the XT control boards, lots of knobs!

Personally i also really like the Yellow Magic korg MS20 filter with the delay. I miss mine … I should build a new one.

Merci maitre (pichenettes)…

Your baby is great, lots of fun ! I admire your work… Just wondering how much it was hackable…

Salutations de Provence !


You’re absolutly right That’s exactly what I think, have other shruthis with different filters, full midi control and this extraordinary sound engine. I had 15 years ago an esqm (another hybrid) but the shruthi is better in every way And I checked the tubeohm page, yes shruthis and ambika still available ! :-)))))))

Filter chips don’t create as much of the tone as you think, how the circuit is designed is foremost what creates the tone. Integrated chips just provide a way to implement a number of components in a compact space.

I’m a user of filters (jd800, gem S3, microwave 2, etc…I have no philosophical problems with digital) and a listener since I get the first Juno reactor in 1994 and the T.I.P records (with the same logo as Mutable) but don’t expect me not to say bs about the technical inside… :slight_smile: On the other hand, many thanx for messaging me back, I love to learn, especially about what I’m fond of…

I read around that the smr4 II is really close to the Roland one, rolandish they say, and I read too that mister Moog (the Olivier one ;) ) does not like his baby to be called rolandish pas taper ! So I might try the rola… the smr4 II instead of the old nippon one…