Discussion about the Korg PolySix synthesizer

Yes, I have been getting acquainted with the Polysix schematics..

I have berm mostly wondering if one might be able to create patch points for things not involving voice pitch, but rather modulation voltages and such. You know, like manually patching MG rate into PWM, allowing PWM fluctuations to be synced with whatever MG is doing (if multing was possible). Or vice versa PWM rate into MG destination. And further it'd be game changing to be able to patch one of the LFO's into another itself, allowing the polysix to have modulated rates of sorts, like if PWM could be effected by MG cv out at a slow rate, then PWM could gradually be oscillating itself.

So yeah, just making patch points for the Polysix's internal CV sends and destinations. That's what I'd like yo do. Seem feasible?

And just to take this one step further.. Would these CV's be functional if physically patched to another synth's CV inputs?

So is this a load of old bullshit or what?  

http://analog.no/cms/index.php/modifications/korg-korg-polysix-noise-reduction



Sent from my handheld device -  please forgive me for mistakes and brevity.  

> On Dec 5, 2013, at 12:42 PM, <jim@saltlands.com> wrote:
> 
> Yes, I have been getting acquainted with the Polysix schematics..
> 
> I have berm mostly wondering if one might be able to create patch points for things not involving voice pitch, but rather modulation voltages and such. You know, like manually patching MG rate into PWM, allowing PWM fluctuations to be synced with whatever MG is doing (if multing was possible). Or vice versa PWM rate into MG destination. And further it'd be game changing to be able to patch one of the LFO's into another itself, allowing the polysix to have modulated rates of sorts, like if PWM could be effected by MG cv out at a slow rate, then PWM could gradually be oscillating itself. 
> 
> So yeah, just making patch points for the Polysix's internal CV sends and destinations. That's what I'd like yo do. Seem feasible? 
> 
> And just to take this one step further.. Would these CV's be functional if physically patched to another synth's CV inputs?
> 
>

Finally, do you have an oscilloscope for debugging?

If you can relate your experience in these areas, it'll affect our discussion of the feasibility of the mods that you've proposed.

Chip

----- You're asking about some non-trivial mods to the synth. You might need to cut/desolder existing components to insert your mods. How do you feel about that?

I'm interested in doing each mod as it appears likely to work, and not be damaging by design. User error is something I can accept, if it happens.

----- How handy are you with a soldering iron?

I'm handy enough. For years I've been handling full recording studio hardware projects in a studio where I just "retired" from being house engineer. But all has been with audio paths (sometimes complex)... Snakes, plates, connections, bays, mults, etc.. No circuits. I just need to get a more accurate set of tools, learn astutely, and be careful.

----- If you end up breaking your Polysix while doing your mods, how sad would you feel (until you hopefully got it working again)?

It would fucking suck. It's my favorite instrument by far. I would be willing to pay a tech to take over and bring it back to life. I know several world class techs. There's a large risk at hand* but also a tremendously musical benefit as well. So it's a chance to take for something pretty cool. And this stuff is fun.

----- Finally, do you have an oscilloscope for debugging?

I can borrow a tektronix from my buddy for a while. Or buy a modern one if I'm going to be doing this a lot more. Got any recommendations on one that's simple and affordable?

----- If you can relate your experience in these areas, it'll affect our discussion of the feasibility of the mods that you've proposed.

Do I pass?

It sure would be exciting to be able to have this developed and posted here on the forum, since everyone can gain from this and choose to mod accordingly.

It looks like there was an autocorrect typo in my original post.. Filter EG frequency.. Was supposed to be CV, not EG.

I'm looking to harness this synth like one would an MS20 or the like. The polysix is simple but versatile, but could be so much more usable. If all of the LFO's could potentially patched to affect eachother, and affect cutoff, affect resonance.. If there could be a trigger input for LFO's to restart, Yada Yada. Etc etc. who knows. It wouldn't just be tweaker results, it would be very musically articulate usable tools. Save a few patch notes with a setting number and it's all recallable. Like a voyager xl but cooler sounding :) I just sold my voyager. Not an xl though.

I'd want to start with TWO mods. Something cv out and something cv in.

If you want to try with one CV out and one CV in, I'd suggest that you start first with using the VCF jack on the back of the Polysix as your CV In. Since it already exists, and should work, it'll be a good place to confirm that you've got your CV Out mod working.

For your CV Out, you get the MG signal out, but since the MG signal is already routed around to many spots (VCA, VCF, VCO), you should probably try to get one of the other CV signals. Maybe you should try for the PWM signal.

The PWM signal is generated on KLM-367. It's on the far right, a little more than half-way down. Look for the text "PW/PWM". If you tack-soldered a wire here, you would have your first CV signal. It would be unbuffered, the wire would easily break off with any handling of the synth, but it would be your first CV signal.

The main problem (beyond the lack of buffering and the lack of physical robustness) is that I don't really know what the signal looks like, so it might not be a very useful CV. Ideally, you'd like that signal to span 0-5V or -5 to +5V. I don't know what it does. You'll have to measure it...

Notice there is a test point marked in the circuit. You should get your multi-meter (aka "DMM") and measure the voltage at the test point on the circuit or at Pin 1 of IC15. Measure the voltage relative to ground, which you can pick up anywhere on the board with a ground symbol. Set your synth for PM. Turn the PW knob all the way low. What's the voltage?. Turn the PW knob all the way high. What's the voltage? That's the span of your signal. Is it 0-5V, or something else.

Now switch your synth to PWM. If you have an O-scope, set it to DC-coupled and use it to watch the CV waveform generated by the synth at this location. Turn the PWM amplitude all the way up. Does it span the same range as when in PW mode? Is it 0-5, or something else?

If the waveform looks useful (again, either 0-5V or -5 to +5V) you could experiment by temporarily jumping it over to the VCF in jack on the backpanel of the synth (or jumping over to the equivalent location on the circuit boards...which looks like KLM-366, down at the bottom of the schematic "VCF fcM In", jump to the correct side of R51.

Good luck!

Chip

An error in my previous reply...when i said "Set your synth for PM", I meant "Set your synth for PW".

And, if you don't have an O-Scope for measuring the PWM waveform, you could set the PWM speed to its slowest speed and use your multi-meter to watch the voltage change. If your meter isn't too slow, you might be able to infer what the voltage range is. You're trying to evaluate whether the range of the PWM is substantially bigger or smaller as when in PW mode. Most likely, it is the same. Since you can trust your PW measurements from your multimeter (because they're DC values, not changing AC values), you can feel confident that you understand the voltage range of the CV signal that you're extracting.

Chip

I had asked Murray (kiwitechnics) this a while back but he wasn't comletely sure because he didn't have a non-kiwisix polysix to test... Would the Kiwi Power Upgrade work ok with a regular polysix?

Thanks everyone for your thoughts. I'm definitely interested in pursuing. I need to thoroughly go over my principals and preparations before jumping in. I'll try the PWM cv out project first, as Chip suggests and kindly offers his generous analysis. Thanks, Chip. Very appreciated and respected.

I'll keep posting here as plans/actions develop. I'm going to be very careful as I don't want to damage anything badly.

I especially need to investigate buffering options, and modifying connections somehow to make things more robust. May need to install some sort of small harness system above the mod point, with a secure connection that doesn't move around at all, and with an adapted larger lead above it going to wherever it needs to go.

I'll probably post here any sort of plan I come up with.

But I'll measure signals first with DMM though, and get an oscilloscope in my hands ASAP.