SMR4 mkII preview
  • I have received 5 protos of the SMR4 mkII. I have assembled one of them and from my point of view there is only minor silkscreen fixes to do (I have wrongly labelled a mod point “HP”, while it’s more a half-assed band-pass). It sounds as I wanted it to sound, and it’s very gratifying to build (lighter ground plane, part count reduced by 20, no tuning). I’ve built 40 or so SMR4 and this was “awww don’t tell me I’m already done”.

    If you are interested in getting your hands on this board rapidly, please contact me privately (“whisper” on this board or by email). I’ll confirm you the availability of a board, and then you can place an order for an SMR4 board on the store and I’ll send you the new board instead. I’m interested in your opinion on the sound and on the build (to promote this as the default filter board with the next batch of kits) so I’d rather see this one go to experienced builders. I don’t feel it’s a “beta-test” though – the circuit is proven.

  • needs moar trimpots. :D

  • Oh, just to be the first and without even knowing if there is any difference between MK1 and MK2 i could not resist stating that the soon to become Vintage MK1 Filter is far superior in every aspect of its sound ;-)

  • It’s impossible fcd, look at this:


  • Ah, thanks, there’s a mistake here! (first term is Vee)

  • @fcd: yes, there is just nothing like that uniquely warm and organic quality of the good old mk1 smr4 sound! plus in the right hands, those three trimpots allowed for unparalleled precision in filter tuning. don’t get me wrong, mk2 sure sounds nice – but it’s nothing like the original. too bad those rare and vintage pre-lawsuit mk1 boards are so impossibly hard to come by these days. :D

  • Pichnettes do u use Latex to write those white paper?

  • @mic.w
    I’m thinking about a single sided reissue of the original MK1 schematics. This time with hand drawn lines for even smoother sound. As we all know, Electrons are Spheres, hence travel better thru silky curves than thru harsh corners. Ill use custom made 0,0014% Caps, Hand Mined Copper, Iron from meteorites found in Antarctica, the Resin for the Boards made of Wale Blubber, Boutique OpAmps whose Die was etched with 24yrs aged Balsamico, refer frequently to the design principles of Rupert Neves 5088 console and polish everything with virgin fairies Pubic hair at full moon. I have to add some more Trimmers to be shure whatever is wrong its in the false settings by the non understanding user and sell this to a ridiculous price in the Maserati Quattroporte Range just to ensure that owner can claim that for this price it must be the hell of a best Filter on this Planets surface – the old Mercedes Benz Trick.
    Want to enroll on my Preorder List? Subscription is only 499€.

    @eatyOne
    i couldn’t solve this Equation even with Mathematica at hand… I’m not capable of anything and I’m not very good at that.

  • @fcd: excellent news! i’ve always said that a high end reissue of the original mk1 board is long past due! but shouldn’t you use pure gold instead of copper? for best results it should probably come from the original golden fleece, but that’s even harder to find nowadays than real vintage mk1 boards. but i guess true inca gold would work as well – provided that it comes from inside a pyramid.

  • @mic.w
    True Mastership is working with copper to make the Sound more grainy. Gold would be to smooth and you’d risk sounding like a VA. But hey – maybe ill do a Gold revision for some Customers down in Dubai. I could even have the substrate for the Transistors cut from Diamonds….

  • i just found an original SMR4 MK1 in my attic when moving houses. My Grandpa used it back in the day.
    i have no use for this any more so i would sell it for 500€

    interested people please email or pm me.

  • This thread is too funny, and too familiar.
  • Hey – you don’t believe in the Capacitor Fairy?

  • Now that I’ve built the MIDIpal, I’d love to see the resistors and caps turn into SMD parts. Seems like 70% of the time is spent bending resistor wires. With SMD it is tin, just place, zap, zap, done.

    Unfortunately, SMD looks scary to anyone who hasn’t actually tried it, so moving to hybrid designs is likely to scare off new customers.

  • @fcd i just don’t believe in their pubic hair. so how do you polish for real?
    anyway i’m in.

  • @rosch

    Scho klar Burschi, where you are there are no more Virgins around…..

  • So who else got a MK 2 proto board!?
    I’ve been enjoying mine.. The MK 1 is definitely good, but I do think this is better.. It seems smoother with better resonance control (less peaky/whistly sounding). It can still sing nicely (self oscillate) yet it can be warm and well rounded too. So it’s a great all round filter I would say. The sound appears to be closer to that of the IR3109 (still my favourite filter).
    And of course there is minimal tuning to do! As it only has 1 trimmer. I doubt anyone is going to miss not having those other 3 trimmers of the original. And the 1 trimmer that it does have is real easy to set..

  • I will miss them badly – i have to search for other neat occupations than trimming good ole SMR-4 s
    I hope Reichelt ships my 220N SOOON so i can try.

  • Are they on the way? I got a couple of spares you are welcome to have if you need them.

  • Should have been here today, GHL says my parcel is here in Nordhorn since yesterday….

  • Really happy with mine too :)

  • I’m in love of this Filter Board…

  • Holy crap, talk about streamlined!!!!

    edit: oops, my point was that 20 fewer components really make a difference, but i didn’t expect it to also be SO SMALL ;)

  • Indeed, if you build it you think “huh, finished???”. Soundwise its great, a slightly bit different but i don’t know if my reference SMR-4 is just tuned a bit odd….

  • A slightly bit different? I thought the difference was more than that.. Which was a surprise given that the core parts are largely the same. Still tuning could of course explain some of the difference. But then thats another thing which is cool about the MK 2. Next to no tuning to do! So one persons MK 2 board should sound nigh on identical to anyone elses MK 2.

    Now that I have spent a week or 3 with it though.. One thing I noticed is the level drop when the resonance is increased. Is there perhaps a way to increase the compensation so the drop is less noticeable? Although maybe this will upset the nicely controlled self oscillation.. ?
    Either way, I still like it a lot just the way it is!

  • Id say its not more different than 2 SMR-4s…...

    But it has Aromaporen ;-)

  • @Luap:

    OK, here’s the secret: there is a 1-pole HP hidden in the compensation circuit. So maybe what you are noticing is not a lack of compensation, but just this bass drop when the compensation kicks in.

    First, try adding a 4.7uF NP in parallel with the 220nF. This is will neutralize the HP effect. Still missing some compensation? Increase R17.

  • Thanks! I may give it a shot next time I have this Shruthi apart. But it is certainly not a big problem or complaint by any means :)

  • I want one.
    If i order an Smr4 in the shop do i get a mkll or do i have to ask for it?
    It might be that i do not need more projects but i can not help it...
    I want one bad.....
    • No step by step assembly photos
    • No assembly instructions
    • No troubleshooting guide
    • No boards produced

    => Project not ready for release yet!!!

    The circuit has been designed, the PCB laid out, routed, prototypes assembled. Only 50% of the work is done.

  • Yups. The Fun part is over, now its hard Work.

    BTW, the Troubleshooting guide will be a short one – its really easy to assemble. No more tedious Groundpads sucking the last bits of Brownian molecular motion from my 8W Iron. HUUUGE 1N Caps fit without a hassle. All in all it makes the Shruthi a real Beginners Project (if the GroundPad Issue on the Contrast Trimmer is resolved someday;-) )

  • "◦No step by step assembly photos
    ◦No assembly instructions
    ◦No troubleshooting guide
    ◦No boards produced

    => Project not ready for release yet!!!

    That was a little sad.
    I think i can do without everything without the board :)
    But is it not ready...then its not ready.
    I am quite eager to get it when its ready.

    :)
  • @jazzdoktorn if you want it sooooo bad, grab it !!! :P

  • Find a PCB house near you that can have a board made from this?

  • Its so streamlined you even could do this on PerfBoard….

  • Thanks for your suggestions but i think i will have to wait until the pcb is out for sale.
  • I am interested in getting more people to build and test this board. If you want to participate, you can order a standard SMR4 board and contact me rapidly by email (olivier ät mutable-instruments dododot net) and I will ship an mkII board as a replacement. I don’t have any bags of parts for those, so no SMR4 mkII kits for the moment (though purchasing a standard kit will give you 95% of the parts for the mkII). This is a slow ramp up guys!

  • And here it is a little video preview of the board :D Link to VIDEO

  • Do I hear my “pythagor” preset in there ? :-)
    Nice one !

  • Yep Pythagor a little beat tweaked but yes :)

  • pichenettes,

    Is the MKII board going to be made available eventually or will it be strictly for kits? Sorry if this has been answered already, I searched the forums but didn’t see this question pop up/answered.

  • Yes, I’ve just added it.

  • oh, what timing!

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