Will the real MS-20 filter please step forward

[Strategy]

this is still on my daydream list but I had to step away from DIY for some months - this summer and fall I had two albums come out, both my bands, local shows all summer, a couple of singles, and tours.

I've stopped all shows for the rest of the year and just fired up my soldering iron the other day - to add a CV input vactrol kludge to the delay time pot of my EHX deluxe memory man! It works!

Your list below sounds amazing! etchable project would be fantastic but if someone did 2-sided boards my offer still stands to coordinate a proto run and eventual group buy...

Strategy

been thinking about this again, and what would make for a good guitar pedal version of this lovely filter.

9 pots: cutoff x 2, res x 2, LFO rate x 2, LFO/CV depth x 2, clean/wet blend

3 toggles: parallel/series a la Rick Holt's suggestion, LFO ramp up/off/down x 2

4 jacks: in/out, CV x 2 (for cutoff, seems more important than res for pared-down version)

2 OTAs, 12 op amps* (in whatever package configuration is most convenient for the Byzantine layout this will end up being), 8 BJTs, yay 50 resistors, 25 caps.
*8 for the 2 filter sections, 4 buffers (VCC/2, input, parallel/series output, blend)

I'm thinking HP/LP switching isn't so important for a MS-20 clone, and any complication of the LFO is doubled. It seems important to have some kind of on-board LFO if we're gonna make this a guitar pedal project, since most guitarist won't have too many modules or synthy things laying around. I think an op amp with rate, depth and ramping is good enough.

Pipe dream? I want to make this an etchable project, but maybe it's too much. 

[garcho]

Bravo! glad to hear it's been a productive season for you. Guess I'll have to buy a few new records now   

Designing a double sided PCB worth fabbing is way beyond my "skills". I'd love to buy a few once we get there, though. I'll put together a big schematic with all the elements. After a few more eyes and ears noodle with it and we get it finalized, maybe we can find a volunteer. Calling Mr. Livingston...

[Strategy]

I still cast my vote for "Frosty" as the project name in honor of the venerable Mr. Paul Perry, erstwhile forum member and designer of the Frostwave Resonator that is the inspiration for this to a large extent.

Strategy

Bravo! glad to hear it's been a productive season for you. Guess I'll have to buy a few new records now   

Designing a double sided PCB worth fabbing is way beyond my "skills". I'd love to buy a few once we get there, though. I'll put together a big schematic with all the elements. After a few more eyes and ears noodle with it and we get it finalized, maybe we can find a volunteer. Calling Mr. Livingston...

[garcho]

Agreed!

[Cliff Schecht]

If you guys pick an LFO circuit you like (or envelope, whatever) I can probably work up both an etchable layout and a two-sided production board over Thanksgiving. Did anything get finalized for this project?

[garcho]

Cliff that's friggin' awesome! Unfortunately, I'm on the road until December, but will be breadboarding as soon as i get home. Any suggestions on the ideal LFO out voltages? I've made a number of LFOs, function generators, etc., but don't know how to make them ideal for the need, I just noodle by ear until they sound good. Anything seem obvious to you so far?

[garcho]

Questions for the gurus:

For this circuit at 9V, ideal full amplitude modulation for the LFO would be ±4.5V, biased from VCC/2 (don't know if I'm saying that correctly)? If it went beyond, would the excess peak cause any problems? The signal would just be clipped and a little squared-off, right?

This is a little premature, but when I eventually get around to the desktop version of this, I was hoping to use Electric Druid's TAPLFO for the on-board LFO. Being a PIC, I am assuming (?) it puts out ±2.5V. Is there a way to amplify the signal without distorting the wave shape?

[digi2t]

I have a Frostwave on the bench right now. I've done a video to demo the controls. One I finish fine tuning it, I'll be getting on with tracing.

I'll post pictures and a schematic as soon as I can.

[nocentelli]

I have a Frostwave on the bench right now. I've done a video to demo the controls. One I finish fine tuning it, I'll be getting on with tracing.

I'll post pictures and a schematic as soon as I can.

Superb. I've got a second looper pedal on indefinite loan, and quite fancy a static filter with HP and LPF to noodle with.

[ml]

That's great!

I put together the Rene Schmitz bipolar version back when this thread was last kicking and I'm about to tear it apart and put it in a modular format.

The frostwave in your video sounds very similar to the Schmitz design and the resonance response is as you describe it--very touchy.

I'm curious to take a look at the frostwave schematic since I'm still on the lookout for the "real" ms-20 filter!

[Strategy]

I haven't had much time for DIY this year but this is likely to bring me back into orbit. Having an MS-20 and having spent a couple of years with a borrowed Resonator I can tell you that they're very, very close in sound - should have bought a Resonator while Frostwave was still around!

[Mark Hammer]

Nice demo, Dino.    I can see why people have so much fun with that thing, and with the Korg original.

The pitch-to-voltage (external input, KLM-129) section of the MS-20 has a similar sort of filter, with variable 2-pole highpass (what they call "low-cut") and 4-pole lowpass.  It is intended to zero in on the pitch fundamental range of whatever it is one wishes to do P-2-V on.  There doesn't appear to be any means to adjust resonance/Q, however.

[deadastronaut]

yeah cool demo dino ,  you might want to check out nick.d's filter...very , very cool...

http://www.diystompboxes.com/smfforum/index.php?topic=104178.msg937481#msg937481

schemo at the top..

[garcho]

Nice D'Astro, did you get that hammered out? That one is really similar to the Schmitz and Schecht versions, which seem to be fairly close to the app sheet 4 pole with added exp current source and buffers. Only so many ways to skin an OTA, right? But it's super funky. Glacially piecing mine together; life keeps derailing me. Knowing Dino is making a vero version will light a fire under my ass to get the single sided etch version done. I'll be holed up in the mountains for the next month with my laptop so it might actually happen. Can't let the strip board guys win!      

breadboarded the Schecht version with TAPLFO and noodled with an envelope follower, i never got far; i just ended up playing my guitar through it for whatever time i had available to work on it because it sounded so rad    multiple LFOs are really nice with this filter.

I figure that the LP>HP board will be big enough, so i plan on keeping the modulation on baby boards. Can't wait until Taylor finally makes a musicPCB board for this. *Ahem*

Speaking of musicPCB, the site is down, anyone know if Taylor's ok? Hopefully just the usual ups and downs of the internet.

[deadastronaut]

^ thats not me, that's 'nick .d's..

he says he's getting it sorted soon... an 8 pot jobby..

[Gila_Crisis]

in my gallery you'll find a vero board layout for a MS20 VCF filter work-a-like. the layout is verified:

http://www.aronnelson.com/gallery/main.php/v/Gila_Crisis/ms20_filter.png.html

[digi2t]

Sorry folks, I forgot to link the Frostwave info here.

http://www.diystompboxes.com/smfforum/index.php?topic=105312.0

Everything you wanted to know, but were afraid to ask. Includes tuning guide.

[Strategy]

Thanks for the updates!!!

[Gila_Crisis]

I've fotgotten to write that I found the schematic at this link:
http://www.aleph.co.jp/~takeda/radio/MS20clone.html

there you find also a pcb layout and some infos as well if can read japanese...
Andgo and take a look on this website, is full of really interesting stuff!

[digi2t]

Andy is working on transferring my schematic to PCB form. I'll be doing a survey soon to gauge interest. If interest is anything like it was for the GIII Dual Fuzz or PLL, production should be a non-issue. By the complexity of the circuit, I imagine board price might sit somewhere between the PLL and the Ludwig, we'll see.