Discussion about the Korg PolySix synthesizer

So I just remounted the entire top of the polysix upward so it faces at a 45 degree angle instead of being nearly flat. It actually looks and feels great, but the real reason I did this is because it was the only solution I could find to avoiding so much noise coming from the synth. I tried everything, from shielding the effects board to unplugging the board and finally completely removing the effects board from the synth. But It turns out the effects board was not the source of noise, it was simply that whenever the whole top of the synth was closed (from being open for repair) and thus the top control panel brought down to normal placement, the entire synth became noisy again.

I had been running a modded patch point that I recently made directly from the signal pre-effects, and when I had the top open and hooked this output up to my mixer and monitors, it sounded spotless. Perfect! No noise at all. But it returned whenever I brought the top down, so I figured why not just remount the top so it sits higher away from things?

Well, it is an incredible improvement to the polysix. The sonic improvement from running directly pre-effects is night and day. I can't speak highly enough.

BUT, in my work, I must have moved cable set somewhere closer to something it shouldn't be near, and now I can faintly hear the sound of digital information being transmitted when I twist some of the knobs, such as the filter. When I move it quickly, it sounds a little like dirty pots, but when I twist it slowly, I can hear one little muffled click at a time.

Any thoughts as to what I might have changed?

But of course!

Here's the non-cleaned up, crusty as-is photos, with bad lighting. Plus the wood sides are temporary. I just wanted to angle it all up and see if it was worth investing a bunch more time in, so I cut some simple wood triangles, freed up some cables harnessing inside, and propped it on up. Sound amazingly clean this way.

https://www.dropbox.com/s/ahj7jjxtojawmlt/Photo%20Dec%2003%2C%205%2019%2053%20PM.jpg

https://www.dropbox.com/s/2qscc4fp9u1vh7y/Photo%20Dec%2003%2C%205%2023%2026%20PM.jpg

https://www.dropbox.com/s/cycy31sw7ofgqlk/Photo%20Dec%2003%2C%205%2022%2017%20PM.jpg

Well, I feel happy with my resolution of the noise issue. So I think I'm squared away. But thanks Coy. I might end up reverting to that if I can't solve this weird digital pot issue that suddenly cropped up. But it doesn't go away when I lean the synth back down, I dont think anyway...............

Just an update.. I tested the proximity relating to my issue..(which is that some of the filter related knobs are sending some sort of extra noise into the signal when I turn them)...

The problem exists the same no matter where the control/top panel is located.. Up/down/etc..

I had stated that maybe this new 45degree angle I've set for top part of synth is somehow the cause of this, but this update is to confirm that it's not.

I do feel I may have caused it in my work, but I have no idea how...

I'd recommend the Kiwisix replacement PSU board - I recently had that fitted to my Polysix by SynthProf, and the reduction in noise on the audio output was very noticeable - I mean we're talking about 6dB kind of improvement, going by my ears.

I've been considering the kiwisix full upgrade for a long time. But also have considered getting just the power supply upgrade and keeping old board. My synth is in great shape inside. Battery was replaced by previous owner. And now it's rather noiseless with the board upright. I'm also unsure about sonic changes that may occur with the full board upgrade. I am completely happy with the way my synth sounds and wouldn't want something to make it sound different.

But mostly right now I just want to get this funny knob sound cleared out. It may be a ground thing, now that I think of it. I currently have the synth's signal/ground diverted before effects, and the effects are left disconnected but powered on. Some of the knobs may be sending ground buzzes each time I turn them because of this incomplete path through original synth layout. I thought it'd be fine because I'm going out somewhere else, but maybe not. So maybe I'll re hook up effects board ground input cable at least, to keep the ground going it's full path.

I've been considering the kiwisix full upgrade for a long time. But also have considered getting just the power supply upgrade and keeping old board. My synth is in great shape inside. Battery was replaced by previous owner. And now it's rather noiseless with the board upright. I'm also unsure about sonic changes that may occur with the full board upgrade. I am completely happy with the way my synth sounds and wouldn't want something to make it sound different.

But mostly right now I just want to get this funny knob sound cleared out. It may be a ground thing, now that I think of it. I currently have the synth's signal/ground diverted before effects, and the effects are left disconnected but powered on. Some of the knobs may be sending ground buzzes each time I turn them because of this incomplete path through original synth layout. I thought it'd be fine because I'm going out somewhere else, but maybe not. So maybe I'll re hook up effects board ground input cable at least, to keep the ground going it's full path.

Great. Well I'm starting to think the knob twist sound is actually something that was already part of the synth by design, and that I'm only noticing it now because my noise floor is lower.. Anyone notice this at all? I'm getting it only sometimes, but I can definitely reproduce it. How about I record it post for you all to hear. Would someone be willing to set their knobs approx the same way and try twisting filter to see if it's a design thing and we all have this in our p6? I can make a simple list of approx dial settings. Should be good enough. If anyone would be kind enough to do this and even record it, that would be really helpful. Post here if you are willing and able.

As for the mod of angling the top panel forward... it's working great. This reduces the noise in my synth very obviously.

And as for the simple mod that I posted involving creating a direct out pre-effects and also a direct input to effects (the mod can be found on this forums "home" page,) that is also a monumental improvement. The big thing is that the signal is no longer passing through the effects section... and more specifically the noise GATE at the tail end of the effects section. This noise gate really limits the subtlety of the Polysix's fundamental sound. I highly encourage anyone to do the mod. The sound is SO much more natural now. Noise gates can really weaken a sound, especially cheap ones. My I/O jacks aren't quite mounted yet (even though I drilled the holes already) because I figured out that i need to order better jacks that have an isolated sleeve, to prevent the lug from contacting the back panel (which causes hum.) But I still have the synth connected to mixer and all is great sounding. Having the panel raised, combined with using direct out pre-effects, makes this polysix on par with modern noiseless synths, but it has the quality polysix fundamental sound still. Amazing.

I definitely agree with the improvement in sound if you take the audio out prior to the effects board. It is definitely more present, clean, and natural. Quite inspiring.

The downside, of course, is that you loose the ability to use the chorus/phase/ensemble effect *and* you loose the ability to route the MG to the VCA. That's a stiff price to pay, but the improvement in sound (and reduction in noise) is worth it in some situations.

The noise gating circuit does sound bad. If you'd like to bypass the gating circuit but not loose the effects of MG-VCA, you can check out my mods (several were suggested and improved by folks here on this board) on my pages below:

Bypass the Noise Gate (or, as I call it, the "Post-Effects VCF"): http://synthhacker.blogspot.com/2013/07/polysix-bypassing-post-effects-vcf.html

Bypass C61 for Extended Bass: http://synthhacker.blogspot.com/2013/08/polysix-deeper-bass-bypass-c61.html

Chip

Chip, thanks for your additions.

I actually just last night saw you had a mod on your site for making the mg delay actually zero. Very cool. I had posted a comment but since we are here... Is it really as simple as swapping out the one resistor for another? That's all that'd entailed? I'm still a bit new to schematics but comfortable learning.

I will check out these other mods too. Thanks very much. Extended bass is enticing.

And yeah, losing the MG->VCA sucks. I was actually thinking there might be a way to get it pre effects board somehow. But that sounds rather adventurous :)

Chris,

I've heard from many sources, in person and online, that people have had success putting insulated foil above the effects board to reduce noise.

So I tried it too. I put a few sheets together and wrapped it in a layer of thin tracing paper on both sides, and added a ground connection to the foil (as indicated in that link you found and posted in the semi-mod thread) and listened very carefully as I brought the top panel down and there was just NOT a bit of difference for me. So maybe it depends on the version/revision of the boards. Who knows. Didn't help mine at all.

But I am VERY pleased with the difference in quality when patching directly out of synth pre-effects. Yes I feel the polysix is awesome with its effects for more aggressive sounds, but the more mellow or deeper palette of sound is hindered by going through the effects section EVEN when they are turned off. This is sorta the point of the mod I cited above. You can avoid the gating/eq'ing that's going on, and it's a huge difference.

I suggest you try the direct feed from voice board (pretty easy even without being comfortable with schematics) and see if you are happy with the difference in quality and noise. I was happy with quality, but not fully satisfied cause I could hear some noise still, so this is when I raised my top panel permanently. Now it's simply stunning how open the synth sounds and with barely any noise at all when a note fades out. Very exciting.

So here's the knob problem I'm having. Anyone heard anything like this? It seems to me like the digital locator signal from the knobs is hitting some sort of grounding issue. I really don't think I've ever noticed this before. It only happens on a few knobs. Cutoff, PW, resonance, EQ intensity. So far I've found anyways.

Sorry for the shrill choice in tone. It reveals the sound the best.

https://soundcloud.com/circuitsynth/polysix-knob-sound

Chris,

I've heard from many sources, in person and online, that people have had success putting insulated foil above the effects board to reduce noise.

So I tried it too. I put a few sheets together and wrapped it in a layer of thin tracing paper on both sides, and added a ground connection to the foil (as indicated in that link you found and posted in the semi-mod thread) and listened very carefully as I brought the top panel down and there was just NOT a bit of difference for me. So maybe it depends on the version/revision of the boards. Who knows. Didn't help mine at all.

But I am VERY pleased with the difference in quality when patching directly out of synth pre-effects. Yes I feel the polysix is awesome with its effects for more aggressive sounds, but the more mellow or deeper palette of sound is hindered by going through the effects section EVEN when they are turned off. This is sorta the point of the mod I cited above. You can avoid the gating/eq'ing that's going on, and it's a huge difference.

I suggest you try the direct feed from voice board (pretty easy even without being comfortable with schematics) and see if you are happy with the difference in quality and noise. I was happy with quality, but not fully satisfied cause I could hear some noise still, so this is when I raised my top panel permanently. Now it's simply stunning how open the synth sounds and with barely any noise at all when a note fades out. Very exciting.

Chris,

I assume you meant the Prophet 08 being too bright and edgy.

I have to agree. The prophet 08 is a great synth with it's own accomplishment and value. But it sounds too modern to my ears.

This mod does not do this to the Polysix. It actually just reveals even more of the Polysix than was audible before, and i don't mean just the highs. It ends up being the kind of synth that when you press a note, you feel like your sitting on the oscillators yourself. It's unmistakably richer and deeper, and simultaneously more transparent and articulate in the high end. Basically it all just sounds like you're finally getting to hear most of the work the design team put into the synth, rather than it being thrown through a few stages of processing.eq'ing/gating/etc.(I'd love to hear opinions from those original Korg guys about their design experiences. Anyone have any links?) It's a very noticeable difference. One that Id definitely call more natural. Like the real sound was let through the door finally.

You gotta try it!

I'll try to post some A/B comparisons here soon.

Also i'll try to post a quick sketch of the wiring. It's very simple. But i admit i was confused two times when i was reading the instructions. If anyone wants to this mod, it's a matter of simple soldering of TS connectors (specific ones though) and drilling two holes in back. If you're comfortable with an iron, you can do it.

Chip here does have some amazing mods posted on his synthhacker site that remove some of the gating/eq'ing from the FX stage. This would allow one to get closer to the richness of the original sound even when not bypassing the FX stage totally.. The side effect of course is that more FX hiss/noise is present, but depending on the patch level it could be totally fine and you'd have more sonic presence as a trade off. I have yet to try this, but for now i'm happy just avoiding the effects since i like the "dry" sound so much.

The real downfall is that when you go through this direct output, you lost one component of modulation.. which is the MG -> VCA. totally sucks. If it's not too far fetched i'd like to someday consider rerouting something to get it back in the pre-affects path. Either that or I'll end up doing chips mods and just patch stuff through the FX-off when i want to use the MG->VCA.

Hi there,

I've been following this thread with interest...

Just an idea (and it certainly could lead nowhere but it's worth a try):

I saw that mention on Chip's SynthHacker blog and thought of you

<img src="http://1.bp.blogspot.com/-n1T7uJfZgec/UefKYP4ytlI/AAAAAAAABjc/73ufJCIV6nI/s400/Quote+From+Manual.png" />

http://1.bp.blogspot.com/-n1T7uJfZgec/UefKYP4ytlI/AAAAAAAABjc/73ufJCIV6nI/s1600/Quote+From+Manual.png

Maybe this is what could cause this weird problem?

Are your keyboard cables all tidy and away from your PCB's?

-Chris, from Synthosphere Labs

That's a very good point: I made sure that the cables are far from IC33. This little section from the service manual must be empirically important.

Yash

Chris, were you referring to me and my problem with strange sounds coming from knobs?

I still haven't sorted this out, but this seems promising, regarding keeping cables away from IC33. I will try this.

It's pretty likely in my case that the problem is being caused by proximity changes because I have lifted my top panel permanently higher and angled forward, shifting a few cables.

Thanks, I will look into this soon.

I recently had some interference when touching the Cutoff bare pot (i.e. without the knob on).

Yash