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WIGGLING 'LITE' IN GUEST MODE

The new 2164 Korgasmatron Dual VCF
MUFF WIGGLER Forum Index -> 5U Format Modules Goto page 1, 2, 3, 4, 5  Next [all]
Author The new 2164 Korgasmatron Dual VCF
Dr. Sketch-n-Etch
I wanted to show off my new MS-20 filter clone. Like the MOTM 420, the Frostwave Resonator, and several others, this filter is based on the later version of the MS-20 filter. However, unlike all the other clones, this one is not a direct (or indirect) copy of the LM13600 OTAs-and-buffers topology of the original. Instead, it is based on the SSM2164 quad VCA chip, and realizes the same transfer function with a VCAs-and-integrators topology. The exponential CV response of the 2164 VCAs obviates the need for exponential converter circuitry. Also, unlike the LM13600-based designs, this filter does not add dc offsets to the signal, and therefore does not require AC coupling capacitors in the signal path.

I've also added a new feature: adjustable limiting voltages in the resonance feedback loops. One problem with the original design (and the clones, I think) is that the resonance amplitude is limited to only 1.8V, and as a result the input signal attenuator has to be set pretty low in order to hear any resonance at all in lowpass mode. My new amplitude control eliminates this problem, and now robust resonance can be obtained without sacrificing signal strength.

Finally, the PCB contains two complete MS-20 style filter circuits, each with all the same features of other popular clones, but with a few additional features as well, including both unipolar and bipolar CV controls, separate three-channel mixer output with optional level control, and optional fine tuning.

A picture of my 4U prototype panel is shown below. This is just one of many panel possibilities, and even this one is missing some of the features available on the PCB for lack of space.

I've also attached some sound clips for your listening pleasure. I'm not much of a production engineer, and all I've got is a little Behringer mixer with no effects and an obsolete version of Cakewalk, so apologies in advance for the crappy sound quality. The last one is my shameless attempt to reproduce the second soundclip on the MOTM 420 webpage with a single filter (the one on the right, if you're curious). This was recorded as a .wav but converted later to an .mp3, so the sound isn't so good, but hopefully the character of the filter still comes through. The other three make use of a triple LFO and my recently redesigned version of Ken Stone's CGS analog shift register, and show some of the formant effects one can achieve with the two Korgasmatron filters in series. However, these only scratch the surface of what this beasty is capable of.

Let me know if you're interested in a handmade PCB.
fonik
Dr. Sketch-n-Etch wrote:
I wanted to show off my new MS-20 filter clone. Like the MOTM 420, the Frostwave Resonator, and several others, this filter is based on the later version of the MS-20 filter. However, unlike all the other clones, this one is not a direct (or indirect) copy of the LM13600 OTAs-and-buffers topology of the original. Instead, it is based on the SSM2164 quad VCA chip, and realizes the same transfer function with a VCAs-and-integrators topology. The exponential CV response of the 2164 VCAs obviates the need for exponential converter circuitry. Also, unlike the LM13600-based designs, this filter does not add dc offsets to the signal, and therefore does not require AC coupling capacitors in the signal path.

impressing.

Quote:
I've also added a new feature: adjustable limiting voltages in the resonance feedback loops. One problem with the original design (and the clones, I think) is that the resonance amplitude is limited to only 1.8V, and as a result the input signal attenuator has to be set pretty low in order to hear any resonance at all in lowpass mode. My new amplitude control eliminates this problem, and now robust resonance can be obtained without sacrificing signal strength.

brilliant
Moog$FooL$
hup hup!!!

another good one Doc., keep 'em comin'!!

Rockin' Banana! SlayerBadger! Play Him Off, Keyboard Cat. applause
numan7
thumbs up right-on doctor e&s - vcf perfection!!! woah hmmmm.... let's see now... maybe i could build just a *small* hihi 5u format system... diy... hmmmm.... dang! tempting.... tempting... hmmm.....

anyways, if there were a nobel synthesis prize, this brilliant design would certainly deserve to be on the list!!! applauseapplauseapplause

kudos,
n7
ndkent
Good work!

Just wanted to mention that adding "tron" to the name at this point makes one, well me at least, assume you were using hacked Monotrons,
Synthbuilder
ndkent wrote:
Just wanted to mention that adding "tron" to the name at this point makes one, well me at least, assume you were using hacked Monotrons,


While I thought of the young Jane Fonda... although it was Klute that did it for me.

Tony
Moog$FooL$
Synthbuilder wrote:
ndkent wrote:
Just wanted to mention that adding "tron" to the name at this point makes one, well me at least, assume you were using hacked Monotrons,


While I thought of the young Jane Fonda... although it was Klute that did it for me.

Tony


lolspew

well at least you're not thinking of an old Jane Fonda....... just wish i knew who or what Klute is??? hmmm..... what was the name of that film??
Dr. Sketch-n-Etch
Moog$FooL$ wrote:
well at least you're not thinking of an old Jane Fonda....... just wish i knew who or what Klute is??? hmmm..... what was the name of that film??

...uh, Klute?
Dr. Sketch-n-Etch
Synthbuilder wrote:
ndkent wrote:
Just wanted to mention that adding "tron" to the name at this point makes one, well me at least, assume you were using hacked Monotrons,

While I thought of the young Jane Fonda... although it was Klute that did it for me.

Well, Tony, you're close. However, I was thinking more Diane Keaton.
nerdware
A very tasty clone! I love the demos too. Thanks. For anyone wondering about that film ref... Klute on IMDB.
russma
...or the good doctor's reference to the "Orgasmatron" from "Woody Allen's film "Sleeper."

thumbs up
keykeyeyekit
This filter drips with awesome.
Moog$FooL$
saw a post on Matrix about this very module.

go Doc. go!!

Rockin' Banana! SlayerBadger! Rockin' Banana!
transfixer
woah woah woah w00t w00t w00t

great sound, nice name!
could it be shrinked into euro format?

zombie
Synthbuilder
Dr. Sketch-n-Etch wrote:
However, I was thinking more Diane Keaton.


Ah... that orgasmatron from Sleeper. I remembered it's usage in the earlier and cheesy film Babarella (that's the Jane Fonda reference) It's the machine that the evil Duran Duran uses on her to 'torture' her. But I see from Wiki it isn't referred to as the orgasmatron but the 'excessive machine'.

And Klute? Ruddy excellent film. Haven't seen it for years though... so it may have aged somewhat.

Tony
Dr. Sketch-n-Etch
transfixer wrote:
great sound, nice name!

Thanks, and thanks!

transfixer wrote:
could it be shrinked into euro format?

I think so. I'm still waiting to hear what the maximum allowable PCB dimensions are for Euro format. My current board is 2.1" x 6.6" which is a little bit long for Euro, I think. I can probably make it about 4" x 4" with some changes to the layout. If it comes to that, I may bite the bullet and get proper boards made professionally. I'm hesitant to do board-mounted pots, because that really locks you into a certain format, and also because only a small fraction of the total pots could be accomodated on the board, so really what's the point?

If you would like to volunteer to tell me what the board size limits are for Euro, I'll think about shrinking my board to fit.
Dr. Sketch-n-Etch
This is the board, by the way. As you can see, things are pretty tight. The two filter circuits are essentially mirror images of each other on opposite sides of the "chip axis". However, I think I could break the circuit at a couple of spots and make the board wider and shorter.





Junk Rhythm
Dr. Sketch-n-Etch wrote:

I think so. I'm still waiting to hear what the maximum allowable PCB dimensions are for Euro format. My current board is 2.1" x 6.6" which is a little bit long for Euro, I think. I can probably make it about 4" x 4" with some changes to the layout. If it comes to that, I may bite the bullet and get proper boards made professionally. I'm hesitant to do board-mounted pots, because that really locks you into a certain format, and also because only a small fraction of the total pots could be accomodated on the board, so really what's the point?

If you would like to volunteer to tell me what the board size limits are for Euro, I'll think about shrinking my board to fit.


On my cases (Elby Subracks) the space between mounting rails is 112.5mm. I would shave off 4mm to allow for a little extra space bringing us to 108.5mm. This would provide a bit more ease in moving modules in and out of the system.

Doepfer's A100P6 cases have a useable depth of 80mm from the front panel to the PSU in the rear of the case. In the sections that do not contain the PSU, the depth is 100mm from the front panel to the rear of the case.
Dr. Sketch-n-Etch
Junk Rhythm wrote:
On my cases (Elby Subracks) the space between mounting rails is 112.5mm. I would shave off 4mm to allow for a little extra space bringing us to 108.5mm. This would provide a bit more ease in moving modules in and out of the system.

Doepfer's A100P6 cases have a useable depth of 80mm from the front panel to the PSU in the rear of the case. In the sections that do not contain the PSU, the depth is 100mm from the front panel to the rear of the case.

Who came up with this midget format, anyway? angry
It looks like I'll have to get this board down to about 4" x 5". That's doable, but not for a couple of weeks, when things at work settle down a little bit.
emdot_ambient
Dr. Sketch-n-Etch wrote:
Who came up with this midget format, anyway? angry

hihi Europeans apparently.

Awesome module, BTW!
Dr. Sketch-n-Etch
emdot_ambient wrote:
Dr. Sketch-n-Etch wrote:
Who came up with this midget format, anyway? angry

hihi Europeans apparently.

Awesome module, BTW!

Touche! (and thanks!)
emdot_ambient
Dr. Sketch-n-Etch wrote:
...I may bite the bullet and get proper boards made professionally...

As in, available for others to purchase? 'Cause I'd definitely go for one.
Dr. Sketch-n-Etch
emdot_ambient wrote:
Dr. Sketch-n-Etch wrote:
...I may bite the bullet and get proper boards made professionally...

As in, available for others to purchase? 'Cause I'd definitely go for one.

Actually, you can buy one now, but it'll be one of my handmade ones. In fact, I sold two just lastnight. I'm (stupidly) charging only $20 (US) + $5 (US) shipping. It'll be one-sided, 2" x 6.6", with tinned traces, but NO silkscreening or through-hole plating -- exactly the same as the board in the pictures below. I'll also send the jumper kit so you don't have to mess with cutting the jumpers to size, and enough documentation to get you through it (it's actually a fairly straightforward build).
Send me a private message if you want to buy a board, cause I'm takin' orders now!
Dr. Sketch-n-Etch
In addition to handmade boards, I thought it would also be nice to offer handmade panels like the one in the picture. This would be in MOTM format, 4U wide, with black graphics baked on bare aluminum with Lazertran. They're very nice looking, and extremely durable.

If you're interested, send me a p.m.
fiveman
For those of us who make boards, are you going to put up a clean template for us to copy and iron on. The photos you posted give a useable image but less experienced etchers may have trouble making up good boards.

Nice layout. A pro version would be a great value and an easy build
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