[PROJECT] - Mut(il)ator

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dKRelease
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[PROJECT] - Mut(il)ator

Post by dKRelease » Mon Sep 16, 2019 9:29 am

Afternoon all.

I'm currently working on my own version of the Mutator which i'm hoping to finish in the not too distant future. Most people will know there are no schematics available for the original, so i'm essentially working from the block diagram in the manual.

Most of the project is pretty straightforward with the no longer available SSM chip being the only issue to overcome. The unit will contain discrete filter circuits similar to the Juergen Haible version of the SSM2040, which can be found online if anyone is interested. The Mutator actually had the 2044 but the 2040 is a superior sounding chip from the information ive gathered, and the consistency of the SSM chips appeared to be questionable anyhow.

I'll be keeping the Mutilator as close to the original as i can, but i'd be interested to hear anyones input as maybe some improvements could be made to the MIDI implementation or whatever else. Cheers.

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yan6
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Post by yan6 » Mon Sep 16, 2019 10:25 am

very cool :tu:, I love rack mount gear and anticipate seeing it's progress and hearing some sounds.

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Post by 4floorsofwhores » Mon Sep 16, 2019 10:46 am

Want. Nice project
Careful now

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Dave Kendall
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Post by Dave Kendall » Mon Sep 16, 2019 11:44 am

Hi.

Nice project. :tu:

Nit-picking a bit I know, but in fact the mutator used the now almost totally unobtanium SSM2045 which is similar to the 2044 but has a VCA onboard.

In terms of changes, the only things I find the original lacking in is that IMO, the LFOs should have been VC LFOs, and that the LFO depths would have benefited from being CV controlled (VCAs in the LFO output path)
ENV SWEEP depth could also benefit from Voltage control.

MIDI control for these three parameters would be very useful indeed.

Personally I'm not bothered by the fact that the front panel knobs don't transmit MIDI.

A wee bit more choice over MIDI controller destinations would be nice too - they are fixed routings in the orginal.

FWIW, the original overdrives nicely if you push it hard. Replicating that behaviour would be worth it I believe. :)
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dKRelease
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Post by dKRelease » Mon Sep 16, 2019 1:19 pm

Dave Kendall wrote:Hi.

Nice project. :tu:

Nit-picking a bit I know, but in fact the mutator used the now almost totally unobtanium SSM2045 which is similar to the 2044 but has a VCA onboard.
Hi Dave. Not at all, i must have misread that somewhere, thanks.
In terms of changes, the only things I find the original lacking in is that IMO, the LFOs should have been VC LFOs, and that the LFO depths would have benefited from being CV controlled (VCAs in the LFO output path)
ENV SWEEP depth could also benefit from Voltage control.

MIDI control for these three parameters would be very useful indeed.
Shouldn't be too much trouble, i'll definitely look into it. I need to swot up on the MIDI to CV and microcontroller side of things as Ive not worked with it much at all. Does anyone have any decent sources of info to get me going?

FWIW, the original overdrives nicely if you push it hard. Replicating that behaviour would be worth it I believe. :)
Im going to do my best to replicate the original using whatever sources i have at my disposal, so lets see what i can come up with!

Cheers

Dan

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jersupereq
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Post by jersupereq » Mon Sep 16, 2019 1:21 pm

Looks cool, will be watching! :yay:

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ryan-Phayder
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Post by ryan-Phayder » Mon Sep 16, 2019 4:32 pm

The Mutator used SSM2045. UTsource has 160k SSM2045 available for about $9/€9 ea

Have you considered the SSI2144?

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Post by jimfowler » Mon Sep 16, 2019 9:26 pm

sign my ass up

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Post by dKRelease » Tue Sep 17, 2019 2:53 am

ryan-Phayder wrote:The Mutator used SSM2045. UTsource has 160k SSM2045 available for about $9/€9 ea

Have you considered the SSI2144?
I decided against trying to source SSM chips as it seems counter intuitive to build a new product around obsolete chips. The fact that UTsource has so many negates that worry but i'm still put off by it. Plus the alleged inconsistency in quality from one unit to the next makes me feel that considering other options makes sense.

As far as the SSI2144, it is a tempting option. Still no VCA but it would make life easier anyway. Have you used/heard them? Some aren't convinced that they sound the same as the 2044 so id be interested to hear peoples thoughts.

Ive built a proto of the discrete version so I could always get hold of an SSI or 2 and test them together. I need to have a think now :hmm:

Cheers

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tobb
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Post by tobb » Tue Sep 17, 2019 4:45 am

Hi ,also planned a clone of this,good you do it,saves me time!

Do not use 2044,sound totally shit,no balls,to weak,and there are already 2044 eurorack filters available..

Forget likely fake 2045 chips from utsource

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Post by dKRelease » Tue Sep 17, 2019 5:07 am

tobb wrote:Hi ,also planned a clone of this,good you do it,saves me time!

Do not use 2044,sound totally shit,no balls,to weak,and there are already 2044 eurorack filters available..
Well this is going to be 2U as the original but I take your point. That's my concern with the 2144 (im guessing that's what you meant?). It seems that as many people aren't convinced by it as those that think it's 'close enough'. Maybe discrete is the way to go.
Forget likely fake 2045 chips from utsource
I am dubious that there are 160000 sought after chips sat there waiting to be bought tbh.

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Post by tobb » Tue Sep 17, 2019 6:12 am

PS what would be nice is if you could also add a link switch 0n/off for the cutoff and reso controls.

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tron23
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Post by tron23 » Wed Sep 18, 2019 6:47 pm

That is great you are working on it, I recall some really nice stereo effects could be accomplished with the Mutator. :guinness:

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Post by dKRelease » Thu Sep 19, 2019 2:20 am

This is a massive long shot, but does anyone happen to have a picture of the MIDI card from a Mutator? I know it was available as an add on but I can't find any info on it anywhere.

I'll be able to sort it one way or another but i'm interested to see how they did it if possible.

Cheers

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Post by tobb » Thu Sep 19, 2019 3:02 am


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Post by dKRelease » Thu Sep 19, 2019 3:19 am

Yeah I have those ones but the MIDI card is concealed unfortunately. Thanks though.

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Post by dKRelease » Fri Sep 20, 2019 2:32 pm

I’m wondering how best to go about setting the operating levels of the modulation sources. Looking at the block diagram it seems that the gate and envelope follower are both positive going only. I’d imagine that the LFO’s are all bipolar, but I suppose the MIDI to CV inputs would also be positive only.

The ‘centre point’ of the filter modulation will be set by the cutoff knob so doesn’t seem as big a deal, although it seems strange to have 2 modulation sources that could potentially be used at the same time operating around a different central level.

My main concern is the VCA triggering. If I’m not mistaken, the gate is intended to completely shut off the VCA (like a gate should) when low, ie 0v. But this would mean the LFO would have no effect for the bottom part of its cycle, and may never allow the VCA to reach full amplitude when operating about GND. Setting the bias higher to utilise the full LFO range would mean the gate would not fully ‘gate’ the signal.

Are there any kind people that could give some insight into how the mutator is configured? Maybe the Softube demo might help me. I think either way some sort of level shift is going to be required and the most logical thing to me would be for the gate, envelope follower, all LFO’s and also the MIDI CV ins to operate in bipolar fashion and then the cutoff and VCA biased accordingly.

I’d be interested to hear peoples thoughts on this.

Cheers
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Post by tobb » Fri Sep 20, 2019 6:10 pm

Imo you have to set it up that way the vca close completely using the gate and convert the LFO signal that goes to the vca control.

Its desired the vca close completely using the gate

Lfo have to be bipolar for vcf mod.

the lfo depth control is missing in you diagram

all controls are available to balance out the desired modulation together with the cutoff used as the offset.

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Post by dKRelease » Sat Sep 21, 2019 1:58 am

tobb wrote:Imo you have to set it up that way the vca close completely using the gate and convert the LFO signal that goes to the vca control.

Its desired the vca close completely using the gate
So assuming that the optimum peak level of the gate/env is around 5v, the LFO should be 5v pp centred around 2.5v? This makes sense, and would allow the lfo full use of range.
Lfo have to be bipolar for vcf mod.


Why is this, given that the Gate/Env will not be? Do you mean because the CV’s are summed and the cutoff sets the centre point of modulation, it is less critical, and the difference in level will be masked?
the lfo depth control is missing in you diagram
Yes this is from the Mutator manual and it has been omitted for some reason

Thanks

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Post by dKRelease » Sat Sep 21, 2019 2:25 am

Double post

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Post by tobb » Sat Sep 21, 2019 5:46 pm


So assuming that the optimum peak level of the gate/env is around 5v, the LFO should be 5v pp centred around 2.5v? This makes sense, and would allow the lfo full use of range.
i think 2.5v its not enough for nice squelchy mods,needs +/- 5v
Lfo have to be bipolar for vcf mod.

Why is this, given that the Gate/Env will not be? Do you mean because the CV’s are summed and the cutoff sets the centre point of modulation, it is less critical, and the difference in level will be masked?


yes


EDIT: PS i recommend out of experience to have the envelope spitting out 10v and not 5v, 5v is not enough for percussive stuff

But 5v is ok for the inverted signal

The SSM2040 shines out with 10v envelopes.

PS: If you add a midi interface in the rack integrates a Midi to cv pitch/note out jack

Then if you add a future 2U oscillator bank rack its getting transformed into a synth and as you use the SSM2040 filter design you get a nice sort of RSF Kobol synth..

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Post by nologin » Sun Sep 22, 2019 3:38 am

Great, is it a personal project with only one unit built, or do you want to eventually provide DIY kits or sell built racks?

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Post by dKRelease » Sun Sep 22, 2019 7:37 am

tobb wrote:
i think 2.5v its not enough for nice squelchy mods,needs +/- 5v

EDIT: PS i recommend out of experience to have the envelope spitting out 10v and not 5v, 5v is not enough for percussive stuff

But 5v is ok for the inverted signal

The SSM2040 shines out with 10v envelopes.


So envelope follower and gate both operating 0-10v? If so, i'd probably have the inverted signal going to 10v also (-10v) as the sweep knob can limit this if desired.

Then the LFO operating +-5v into the filter, but shifted up to 0-10v for the VCA input so the LFO and Gate/Env are both able to cutoff the VCA at their lowest level. Does this sound right?
PS: If you add a midi interface in the rack integrates a Midi to cv pitch/note out jack

Then if you add a future 2U oscillator bank rack its getting transformed into a synth and as you use the SSM2040 filter design you get a nice sort of RSF Kobol synth..
I'll look into this, thanks

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Post by dKRelease » Sun Sep 22, 2019 7:39 am

nologin wrote:Great, is it a personal project with only one unit built, or do you want to eventually provide DIY kits or sell built racks?
All my projects are personal but PCB and panel kits will be available to those who want them. Probably wouldn't be looking to build them myself to be honest.

Cheers

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Post by dKRelease » Sun Sep 22, 2019 8:20 am

New tweaked layout. Usable space in the Adam Hall enclosure i got from Thomann is less than whats in the Mutator. I'm designing around this smaller size of just over 400mm internal width so the PCB's are compatible with all 19" rack cases.

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