Filter board revs - time waits for no builder

Hey helpful electro-technik-musos,

I’m finally getting around to building my Shruthi-1. I have to build it before my Anushri gets here :slight_smile: I notice that in the ten or so (Olivier Gillet) years since I ordered it, the SMR-4 board has a new rev. I have SMR-4 rev 0.5, and a CEM 3379 rev 0.3. Is it worth ordering a new board before I start? What are the main deltas between the latest SMR-4mkII and the v0.5? Sorry, I did spend a bit of time searching the forum, but broke down and am asking for a link/info/opinions. I don’t see the CEM board on sale anymore. What is a reasonable price to pay for a 3379 on ebay these days? I don’t want to contribute to price inflation… Thanks! minphase (KevinC)

they go for between 25 and 35 US$ (or maybe even euro, i’m not sure, IF they are available)
maybe you’re lucky

as for the filter:

Original release.

v0.6, v0.7

Removed middle spacers holes.
Self-oscillation in 2-poles mode.
Increased hole sizes for audio and DC connectors.
Added pads for external CV sources on cutoff.

from here
no reason to throw this away and buy a mk2!

The most important difference between the SMR4 v0.5 and the v0.7 is that the v0.7 has self-oscillation in 2-pole mode (on the v0.5 resonance in 2-pole mode is more a kind of phasey/feedback effect). The most important difference between the SMR4 mkII and the SMR4 is that on the mkII the resonance is “sweeter” (high-pass filter in the compensation circuit) - and that overall the circuit is more intelligently designed - with less buffering between stages. The CEM3379 board you have is the most recent one - I think I have done a revision after that, but with cosmetic changes only.

Thanks, Rosch! I found the new mk2 and older build guides about 5 mins after posting. I see a slightly smaller parts list for the mk2, no biggie as I’ve got the parts that came with the original kit. I would like to control the cutoff via CV, though. The CEM build guide has disappeared, anyone got a copy? I believe Olivier has removed the CEM and IR3109 and SSM guides to prevent wholesale ransacking of old ESQ-1s, Matrix-1000s and Boss phaser pedals…

Thanks, Olivier. If I order a plain mk2 PCB, does the webshop automatically add 20 euros to ship to US? Or is it smart enough to know that a board fits into an envelope? Sorry to take space in main list asking this. Best, mp

It will add only 5€ if you buy a filterboard.