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This vintage synth today is highly sought after of, It was Korg’s answer to the Roland Juno Series, but this one here goes a bit further it was properly upgraded and installed with the Moog Slayer Mod: which massively expand the functionality of the analog filter inside the poly 800 synthesizer. The “moog-Slayer” modification involves externally mounting the trim pots for adjusting VCF cutoff and resonance. With this modification the internal VCF CUTOFF (parameter 41 and VCF RESONANCE (parameter 42) acts as a master setting for the particular patch. The added controls can only sweep down from this setting, so be sure to set them high. BE CAREFUL with this modification the filter will oscillate if the resonance is set to 13 or higher.
Also installed is a Filter Input.The Filter input allows you to run any line level audio signal into the poly 800. The audio will be affected by the VCF, VCA, and Chorus and come out the keyboards main output. This filter input has a level control so that you can mix the audio with the keyboards internal voices. If you want to pass just audio, make a patch here just DCO 1 is on. Turn all the individual tones off (4′, 8′. 16′ etc) make sure the level for oscillator 1 is set pretty high.
Upgraded Blue Display
Brand New Internal Battery installed (good for years), also has a Battery Holder, so internal battery is User Installable.
Generic AC Adapter Included with voltage range from 100-240v
Inputs/Outputs Have Been Cleaned
Unit Works Great” Click here to search for synths on eBay
“USED Vintage Korg Polysix Synthesizer. Selling as is for PARTS / REPAIR due to age, cosmetic condition and the issues I know of.
” Very good condition- inside and out as you can see by the photos. I have been repairing consumer and pro gear since 1979 and all my gear has been well cared for and maintained to a Tee. All controls, switches and input/output jacks have been thoroughly cleaned and deoxidized. All tact switches work as if new. The electrolytic capacitors have all been checked for excessive ESR and the voltage regulators scoped for excess ripple and proper output. I have also replaced the soldered-in memory backup battery with a battery holder so the backup battery can be easily changed in the future. I have owned this little beauty for about 20 years and it has seen very seldom use. I’m going through all of my gear, refurbing it all and reluctantly letting it go. It comes with the power supply, both the Owner’s manual and Service manual in digital form (PDF) and the factory sysex downloaded directly from Korg’s website. There are several sites that you can get free patches from which can be downloaded and imported via midi or the tape input. The power supply is included but is not original. Hoping it goes to a good home that will appreciate it for what a gem it is!” 
“Kork Micro Preset M-500 SP Analog Vintage Synth. Condition is Used.
“Korg Poly-800
“80s poly synth, amazing lo fi sound. ” 
“Excellent condition, no functional issues, no exceptions. Includes new power supply. All buttons and knobs work without issues.” 
“Korg ex-800. Missing button cap but working good. Great 80’s sound 6 voice synthesizer. Condition is Used. ”