Overdrive Mod for Korg Polysix

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chipaudette
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Overdrive Mod for Korg Polysix

Post by chipaudette » Thu Dec 10, 2015 6:09 pm

Hi All,

After adding velocity sensitivity to my Korg Polysix, I was able to get sounds in vein of electric piano / clav. It made me pretty excited. The sound from the Polysix was too clean, too dynamic, to be fully satisfying for EP / clav. So, I started to look into adding some overdrive or distortion to give me a little grit and a little compression.

At first, I tried diode based distortion, but I didn't like the sound very much. Demo here:

http://synthhacker.blogspot.com/2015/11 ... rtion.html

Then, I tried overdriving one of the OTAs in the Polysix's signal path. I liked that a lot better. Demo here:

http://synthhacker.blogspot.com/2015/12 ... drive.html

Now I've got to figure out how to package it up so that I don't have clip leads and resistors hanging out of my synth...

Chip

chipaudette
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Re: Overdrive Mod for Korg Polysix

Post by chipaudette » Wed Dec 23, 2015 5:19 pm

I'm starting to figure out how to make my overdrive mod controllable from the front panel and how to make it be saved/recalled from patch memory. The core of the solution is an Arduino + digipot. The trick to getting patch memory is that I'm re-using the low end of the Polysix's "Attenuator" knob.

If you're interested, you can check it out here:

http://synthhacker.blogspot.com/2015/12 ... drive.html

Chip

Mooger5
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Re: Overdrive Mod for Korg Polysix

Post by Mooger5 » Wed Dec 23, 2015 7:43 pm

the j201 fet emulates tube saturation better. the trend in the stompbox world is to clone the preamp section of a classic tube amp with the identical circuitry but using a j201 in place of the triode. Powered by 9 volts, obviously. I did a side by side comparision with two dr boogie stompboxes and a Mesa dual rectifier and it's almost a close match.

Also a cabinet simulator will add the extra tone colour you seek.

Worth checking runoffgroove.com for schematics and demos. listen to the Uno and the condor cab sim.

Also Circuit Snippets by tim escobedo. The schematics are around.
Herrare umanum est.

chipaudette
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Re: Overdrive Mod for Korg Polysix

Post by chipaudette » Sat Jan 02, 2016 12:56 am

That's pretty good feedback regarding the FET-based overdrives. I'm a guitarist, too, so that interests me. I've never been a fan of distortion boxes...I always preferred the sound of overdriving coming from the amp itself (even pre-amp overdrive is better to my ears when it's in the amp). I'd be curious to try some of these FET-based overdrives myself.

Chip

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Re: Overdrive Mod for Korg Polysix

Post by chipaudette » Sat Jan 02, 2016 12:57 am

Back on the OTA Overdrive using the Polysix's OTA, I've designed a custom PCB to put all the elements together. I'm wicked excited...

http://synthhacker.blogspot.com/2016/01 ... drive.html

For the design itself, I used Fritzing, which I hadn't used before. In my one other PCB (a MUCH simpler design), I used CadSoft Eagle. Eagle may be used by a lot of hobbyists, but it definitely isn't aimed at hobbyists. I found Fritzing to be way more approachable. It was even kinda fun.

Chip

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synthroom
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Re: Overdrive Mod for Korg Polysix

Post by synthroom » Sat Jan 02, 2016 8:31 pm

Thanks for post your blog. Very cool. And the fritzing.Com link looks very useful as well.
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Mooger5
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Re: Overdrive Mod for Korg Polysix

Post by Mooger5 » Fri Jan 08, 2016 10:31 am

chipaudette wrote:That's pretty good feedback regarding the FET-based overdrives. I'm a guitarist, too, so that interests me. I've never been a fan of distortion boxes...I always preferred the sound of overdriving coming from the amp itself (even pre-amp overdrive is better to my ears when it's in the amp). I'd be curious to try some of these FET-based overdrives myself.

Chip
Forgot to mention the Fetzer Valve. http://www.runoffgroove.com/fetzervalve.html
Herrare umanum est.

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