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 Forum index » DIY Hardware and Software » Jürgen Haible designs
MS-20 based SEM / Polysynth ?
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jeffery girlsbottom



Joined: Jun 22, 2008
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PostPosted: Tue Sep 16, 2008 8:30 am    Post subject: Reply with quote  Mark this post and the followings unread

are there any other DIY polysynths out there which I could investigate, whilst waiting for this one?
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urbanscallywag



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PostPosted: Tue Sep 16, 2008 2:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

jeffery girlsbottom wrote:
yeah i would def buy one or two of these. a polyphonic homemade synth is something that needs to be done. very exciting. can you have the same waveshaping function as on the ms-20? so that you can feed a live external source/signal of a sample or whatever and manually tweak the waveshaping to fuck with the processed sound?


Do you think that having an MS20 ESP feature on a polysynth would be useful?

I guess with something like a hex-pickup guitar maybe it could be, but it seems like other processing is left best to mono and modular synths.
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phdinfunk



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PostPosted: Wed Sep 17, 2008 4:24 am    Post subject: Agreed! Reply with quote  Mark this post and the followings unread

"I guess with something like a hex-pickup guitar maybe it could be, but it seems like other processing is left best to mono and modular synths."

Yea, I don't think that's really necessary here. Of course, you could run sounds through the filters... actually it would work as a four (or more) voice resonator filter, you could pan the filters and way you wanted and have indy LFOs for each one. I did this with a FVS1... it's cool.
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Electronicant



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PostPosted: Wed Oct 22, 2008 11:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi. The KORG MS-20 is mentioned as an alternative to the SEM. But how about the KORG Delta? it has some unusual designs and a very characteristic and good sound. It´s VCO is controlled from four pitch sliders 16', 8', 4', and 2'. Each of these harmonics is a square wave but can be turned into a saw wave. Useful and intuitive.

The VCF is a 24 dB/oct LP/BP/HP with resonance. I think its the only KORG with that filter. I wonder why KORG did´nt continue using this filter in the following synths; Mono/Poly, Polysix and Trident. Anyone who know how this VCF is compared to the KORG 35 VCF?

Here´s some wonderful pads and more: http://homepage.mac.com/synth_seal/html/ds_delta.html

Last edited by Electronicant on Thu Oct 23, 2008 12:17 am; edited 2 times in total
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jhaible



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PostPosted: Thu Oct 23, 2008 12:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Electronicant wrote:
Hi. The KORG MS-20 is mentioned as an alternative to the SEM. But how about the KORG Delta? it has some unusual designs and a very characteristic and good sound. It´s VCO is controlled from four pitch sliders 16', 8', 4', and 2'. Each of these harmonics is a square wave but can be turned into a saw wave. Useful and intuitive.

The VCF is a 24 dB/oct LP/BP/HP with resonance. I think its the only KORG with that filter. I wonder why KORG did´nt continue using this filter in the following synths; Mono/Poly, Polysix and Trident. Anyone who know how this VCF is compared to the KORG 35 VCF?

Here´s some wonderful pads and more: http://homepage.mac.com/synth_seal/html/ds_delta.html


I thinkt the reason why Korg didn't use that filter in their "true" polyphonics is that it's quite a big circuit. (AFAIK there is only one VCF in the Delta, but it's been a while since I've looked. Incidentally I have a Delta with broken VCF in the garret. I had bought this - broken - because I wanted to use the keyboard action for my PS3200 clone, but when I found it hat just a damaged filter, I decided I'd restore it some day.)

JH.

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Electronicant



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PostPosted: Thu Oct 23, 2008 12:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Maybe a filter to make a stand alone clone of. I have´nt seen any clone of it yet.
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fonik



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PostPosted: Thu Oct 23, 2008 12:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Electronicant wrote:
Maybe a filter to make a stand alone clone of. I have´nt seen any clone of it yet.

tom gamble once made one (EFM 46212 VCF, 4600er series):
http://www.modular.fonik.de/files/EFMforum/orgEFMfiles/efm-4600-doc_01.pdf

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phdinfunk



Joined: Jun 04, 2008
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PostPosted: Thu Oct 23, 2008 8:07 am    Post subject: Whoa! Reply with quote  Mark this post and the followings unread

That sure looks a lot like an SEM filter, and a later MS-20 filter.

I would rather have a Korg 35 style MS-20 filter.

What's neato is that Tom Gamble turned me on to breadboarding stuff on a Perfboard. I spent maybe six months after that fooling around with filter circuits. At first I just kept seeing how far out of spec I could make the componant values and it still work, then I started adding germanium diodes to ground for clipping, or diode linearizing crap in the feedback of filters. (maybe even MOSFETs arranged as diodes, hard to remember, this was almost ten years ago)... The only thing I had ever gotten to work prior to those filters was a few distortion boxes I had built... (do you see the connection?) I remember it usually working out just fine to screw with stuff in the feedback loop.

I built one where I put a diode clipping section like that into an SEM type filter topology. I never made it into four poles though, that's pretty cool.

--Jonathan
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Noiseconformist



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PostPosted: Thu Oct 23, 2008 6:19 pm    Post subject:   Reply with quote  Mark this post and the followings unread

Electronicant wrote:

The VCF is a 24 dB/oct LP/BP/HP with resonance. I think its the only KORG with that filter.


Is it really a -24dB/Oct. HP in there? Wow!

Michael.

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Electronicant



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PostPosted: Fri Oct 24, 2008 3:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Noiseconformist wrote:
Electronicant wrote:

The VCF is a 24 dB/oct LP/BP/HP with resonance. I think its the only KORG with that filter.


Is it really a -24dB/Oct. HP in there? Wow!

Michael.


Not shure, actually. It´s a bit confusing. Vintagesynth states "...24db/oct low pass filter (high pass and band pass options are included too)..."

And Tom Gamble´s notes says "Selectable HP, BP", but it looks like a mistake. The picture of the clone has selectable LP/BP, like the Delta´s panel switch.
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Noiseconformist



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PostPosted: Sat Oct 25, 2008 5:36 am    Post subject: Reply with quote  Mark this post and the followings unread

I looked up the schematics, it's LP/BP Sad
I think its pretty hard to get an efficient topology and circuit for -24dB HP/LP.

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widdly



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PostPosted: Thu Oct 30, 2008 11:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you wanted to build a polysynth but NOT in the SEM style, then everything needs to be voltage controlled. I like this approach since it will keep costs down (1 knob for each parameter instead of 1 knob for each parameter x number of voices).

This is not problem for VCO, VCA and VCF which are more often than not completely voltage controlled (aside from the resonance but that's just a case of an additional VCA).

However, simple circuits for fully VC LFO's and ADSR's are hard to find. The best option (simplest, cheapest and smallest) I've seen are the PIC based ones from electric druid.

Of course there are some other considerations. Switching oscillator wave shapes could be addressed with some CMOS switches. Mixing the two oscillators into the VCF could be handled by an inverter and an additional VCA.

It would be great if the boards could be designed to accommodate either approach to building a polysynth. Additionally, if the boards were completely voltage controlled, the ambitious builder could create a system for storing/recalling presets.

Last edited by widdly on Thu Aug 05, 2010 10:05 pm; edited 1 time in total
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jhaible



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PostPosted: Fri Oct 31, 2008 4:09 am    Post subject: Reply with quote  Mark this post and the followings unread

widdly wrote:
If you wanted to build a polysynth but NOT in the SEM style, then everything needs to be voltage controlled. I like this approach since it will keep costs down (1 knob for each parameter instead of 1 knob for each parameter x number of voices).

This is not problem for VCO, VCA and VCF which are more often than not completely voltage controlled (aside from the resonance but that's just a case of an additional VCA).

However, simple circuits for fully VC LFO's and ADSR's are hard to find. The best option (simplest, cheapest and smallest) I've seen are the PIC based ones from electric druid.

Of course there are some other considerations. Switching oscillator wave shapes could be addressed with some CMOS switches. Mixing the two oscillators into the VCF could be handled by an inverter and an additional VCA.

It would be great if the boards could be designed to accommodate either approach to building a polysynth. Additionally, if the boards were completely voltage controlled, the ambitious builder could create a system for storing/recalling presets.


That's precisely what the JH-4 was. Everything voltage controlled, and switching made with FETs and OTAs.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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widdly



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PostPosted: Sun Nov 02, 2008 7:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nice. I hadn't noticed the jh4 on your site before.

What envelope did you use? I'd be interested in a schematic if there is one available. Simple VC-envelopes are hard to find.

Last edited by widdly on Thu Aug 05, 2010 10:05 pm; edited 1 time in total
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jhaible



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PostPosted: Thu Nov 06, 2008 5:50 am    Post subject: Reply with quote  Mark this post and the followings unread

widdly wrote:
Nice. I hadn't noticed the jh4 on your site before.

What envelope did you use? I'd be interested in a schematic if there is one available. Simple VC-envelopes are hard to find.


It's a LM13600-based VC envelope that I don't recommend because of offset issues. I was lucky with the 13600 specimens I've used, but with other 13600's you may run into trouble - I won't publish such a circuit.
What I recommend instead is the use of my 4-transistor cell I've used for the MOTM VC LAG, which in retrospect looks like a Class C version of the famous Blackmer VCA - or simply use a Blackmer (THAT) VCA.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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Electronicant



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PostPosted: Wed Nov 12, 2008 4:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi.

Another idea came up of a simplified version of this Polysynth. One could build a divided down machine, like a string machine. Sometimes thin sounds are desirable. It indeed results in warmth and nuances (but not more fat) to build up sounds from several thin layers. Just like a Rembrandt painting, or like keeping you warm in cold temperatures; several thin layers of garments gives more warmth than one thick!

Add top octave divider circuitry to the board and only one board would be needed. To make the sound a bit thicker, one could add a board per instrument layer/section; build a three section ensembler with one board for strings, one for brass and one for human voices. (2 VCO:s per board ofcourse). Advantages compared to other existing stringers/paraphonics/ensemble synths is that you can design it after your own taste.

1. You can choose a larger keyboard, (most stringers use four octaves).
2. Velocity, AT possible?
3. Choose whatever filters and presets you like. Like the FFF, which could be built so that all presets could be used independent simultaneously.
4. VCO architecture with indepenent simultaneous pitch range controls, like on KORG Delta. Wide range up to 6 octaves or so.
5. Multiple Trigger mode as an alternative to individual VCA EG:s per key as on Lambda.
6. Portamento.
Etc..
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jhaible



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PostPosted: Wed Nov 12, 2008 11:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Electronicant wrote:
One could build a divided down machine,


Certainly interesting on it's own, it's pretty far from what I intend to make.

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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Electronicant



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PostPosted: Wed Nov 12, 2008 12:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
Electronicant wrote:
One could build a divided down machine,


Certainly interesting on it's own, it's pretty far from what I intend to make.

JH.


Yes, as a final instrument it´s far from it and we could start an own thread about it. It would be an appropriate instrument to house JH phasers, choruses and FFF as built in devices. The polysynth board seem to be a good starting kit as it has so many options, therefore I posted it here.
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TekniK



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PostPosted: Fri Nov 14, 2008 6:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,nice to discover the 440 came from ur proto project,very ,realy very good clone,but when i compared to a 2040 just a little (very little) less precice,probably due to sync between the 4 poles?

Anyway i would not include a 24db in this project,u should be able to obtain a close sound to the sem multimode filter using a simple 13700 based design...

Keeping the voice not to complex would be + point,a little card,so we can finaly build our 8 or 16v dream synth!

just make sure to provide a cv fo the filter mode (the biggest error oberheim did on there sem not to include it)

Regards
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Electronicant



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PostPosted: Mon Nov 17, 2008 10:16 am    Post subject: KORG VS Yamaha VCO Reply with quote  Mark this post and the followings unread

Hi.

As it´s the linear effect which is intended in this project, in what way is KORG´s VCO design to prefer in front of Yamaha´s?
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jhaible



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PostPosted: Mon Nov 17, 2008 4:29 pm    Post subject: Re: KORG VS Yamaha VCO Reply with quote  Mark this post and the followings unread

Electronicant wrote:
Hi.

As it´s the linear effect which is intended in this project, in what way is KORG´s VCO design to prefer in front of Yamaha´s?


Is it?
I like them both ...

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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whomper



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PostPosted: Fri Jan 09, 2009 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

J.H.,

Any serious thoughts on this project at present?

I am looking out for something in these lines (poly synth) in an expansion card like fashion.

Is the plan to get 4 notes per card?

I am not so picky with respect to which filter design is included, and I will probably look for a Midibox Midi2CV 8 CV board in order to have 8 notes polyphony.

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jhaible



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PostPosted: Fri Jan 09, 2009 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

whomper wrote:
J.H.,

Any serious thoughts on this project at present?



Right now I'm still in the final stage of the Subtle Chorus project (documentation and shipping).

Then I'll take a look what comes next. I don't know it myself, yet. I'll start drawing circuits for various proposed projects, and watch out which develops a life of its own. Smile

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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Tenine



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PostPosted: Sun Jan 11, 2009 7:56 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
widdly wrote:
Nice. I hadn't noticed the jh4 on your site before.

What envelope did you use? I'd be interested in a schematic if there is one available. Simple VC-envelopes are hard to find.


It's a LM13600-based VC envelope that I don't recommend because of offset issues. I was lucky with the 13600 specimens I've used, but with other 13600's you may run into trouble - I won't publish such a circuit.
What I recommend instead is the use of my 4-transistor cell I've used for the MOTM VC LAG, which in retrospect looks like a Class C version of the famous Blackmer VCA - or simply use a Blackmer (THAT) VCA.

JH.


I've been planning a simple polysynth recently. One thing that really got me stuck was trying to find a simple VCAR EnvGen.
I couldn't find your 4-transistor cell anywhere on your site, maybe I'm looking in the wrong place... Would you share the schematic please?
Thanks.
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jhaible



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PostPosted: Fri Feb 06, 2009 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's another idea - a variant that might be interesting, as it bridges several classic synth concepts:

One board could contain
1 VCO (with linear Detuning option and PWM)
1 HPF (MS-20 style)
1 LPF (MS-20 Style)
2 VC envelopes
1 VCA

This would open certain possibilities:

1 Board = something like a MS-10, but with MS-20 filter and two envelopes

2 Boards = a voice with CS-80 architecture (each VCO has its own HPF and LPF!) - just talking about architecture - it's still the Korg filters.

4 Boards = a simple single-VCO polyphonic a la Oberheim Four Voice

8 boards = a very powerful Four Voice synth with Korg filters and CS-80 architecture

16 Boards = powerful 8-Voice polyphonic

etc.


Interesting?

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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