Korg Poly-61 Oscillator Waveforms

YouTube via rolandsh1000.

follow-up to this post.

"Just a short video showing the two "types" of sawtooth waveform on the Korg Poly-61. The Poly-61 has two oscillators: DCO1, a digitally-reset analog sawtooth-core oscillator (much like that on the Juno-6, -60, -106) and DCO2, a coarse, divide-down-style oscillator, based upon a CD4520 counter and some summing resistors.

I think both are musically useful, but it's telling that Korg gave the user the ability to turn off _only_ DCO2; DCO1 is always on!"

Knob Laden Heavily Modified KORG Poly-61 Analog Synthesizer SN 724389 w/ MIDI In

Note: Auction links are affiliate links for which the site may be compensated.

via this auction

"This is a very unique instrument. This Poly-61 was modified to bring a lot of the settings to the front panel. As you can see from the pictures, a total of 12 knobs have been added, as well as 12 rocker switches. The purpose of these mods was to allow hands-on, real-time editing of the synth's various parameters -- something that was impossible on the original Poly-61.

Although I'm not 100% sure, I am virtually certain that this is the instrument that was modified by a YouTube user named "rolandsh1000" who was apparently either an engineer or an incredibly knowledgeable hobbyist. If you search YouTube for his channel (put in the term "rolandsh1000 channel" without the quotes and you'll find it), you will see that he put out a series of two videos in 2009 and one more in 2011 about how he modified this synth and what the various mods do. [see here for all three] I strongly suggest that you check them out. I bought the synth from Perfect Circuit Audio about three years ago, here on eBay.

One huge bonus? It's got MIDI in! So unlike the original Poly-61, you can at least connect it to a sequencer or your DAW."

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Modified Korg Poly-61Synthesizer

YouTube via rolandsh1000

"Demo of my modified Korg Poly-61. I got it for cheap off local Craigslist because of some issues. The most problematic was the non-triggering keyboard. I swapped out the keyboard PCB from a dead Korg DW-6000 and now it works perfectly (I recommend if you can find a dead DW6k and you're trying to repair a Polysix or Poly-61, you'll be amazed how much better the DW6k keyboard works).

Anyway, the P-61 is a lot like a Juno-60 or -106, in that each voice has one real digitally-controlled sawtooth core oscillator (DCO), VCF, and VCF. So it's essentially an analog polysynth under digital control. What it has over the Junos: an extra true-digital oscillator (fairly lame, but useful for some things), real analog envelopes, two LFOs. What the Junos have over the P61: chorus and, most importantly, analog controls to tweak all parameters.

The P61 designers apparently wanted to save money and followed the lead of the Rhodes Chroma and Moog Source in the user interface, so the P61 used a digital button interface to adjust parameters settings. IMO, this sucked because 1) it inhibited sound exploration 2) the resolution on the voice and modulation parameters was limited.

So, I decided to bring out a lot of these parameters of the P61 out to the panel and convert them to true analog control. This meant that these parameters could not be stored in patches (though other parameters still would be), but I was willing to forgo that since I basically just play for fun, not on stage. The parameters I brought out were the global ones (changes made by the microprocessor to all voices at once), which made it easy to have one knob or switch control all voices - all my mods are either switches or resistors/pots, no active electronics were added. I think you could make ALL of the parameters under analog control, but to go beyond what I did, you'd have to modify each voice circuit, which is a lot more work. :)

Controls added:
DCO1 waveform switch (saw, pulse)
DCO1 PW/PWM switch
DCO1 PWM amount
DCO2 on/off 'harmonic' switches: 2', 4', 8', 16'
VCF cutoff
VCF resonance
VCF keyboard tracking switch
VCA EG/gate switch
MG frequency
MG waveform (tri, squ)
MG DCO amount
MG VCF amount
Joystick:
- LFO2 waveform (tri, squ)
- LFO2/cutoff switch
- Joystick/Knob select switch (vertical joystick disabled in favor of rotary knobs)
- LFO2 DCO amount
- LFO2 VCF amount

In sum, these synths seem quite inexpensive for what's inside and with this added analog control (now it's somewhere between a Juno-6 and -60 as far as patch storage and user control), it's a lot more fun to play!"

Korg Poly-61 LeftHand Panel Mods

YouTube Uploaded by rolandsh1000 on Jul 12, 2011

"Just a short video detailing the left-hand panel mods for a Poly-61 I'll be selling on ebay soon (my other video shows the full-blown modifications to a different Poly-61, whereas this one still has the stock digital parameter access and patch storage).

This P-61 also has the p6retro MIDI input, a new Lithium battery, all keys work fine, and has been calibrated."