The filter FM needs a lot of harmonics to work with, so playing an interval like a fifth really works well. You can do that with the chord memory, or in double mode you can set the DC0 2 interval (parm 31). I don’t think the internal sequencer works when you are using chord memory so if you need the sequencer you will have to use a double mode patch to get the interval. Set the cutoff way down low, the resonance way up, and add a touch of FM.
I have also been thinking of adding a noise level knob, mostly because if interactions with the external input I added. There seem to be three choices when it comes to where to inject the external input signal into the VCA/VCF (DCO1, DCO2, Noise). I currently have it connected to the DCO1 input but was thinking of moving it to the noise input. In that case, I believe parm 33 would need to be up high to let the external sound through but then I would get noise too, so a separate knob for noise level would be essential. I would be very interested in hearing from people who added an external input to see how they did it. There are definitely tradeoffs among the choices.
As for adding the noise knob, it might be as simple as replacing VR3 with a full size potentiometer. It would take some testing to determine the exact value to use, and R34, R35 might need to be changed so you can get the minimum noise level down closer to zero. The current value of VR3 (1 Meg) will take the noise level well above the factory spec of 0.3V p-p, so you have to be careful there. It might be easier to put the pot from IC2 pin2 to ground. Like I said, this needs some testing unless someone else has already done it.
Don Backshall
From:
korgpolyex@yahoogroups.com [mailto:
korgpolyex@yahoogroups.com ] On Behalf Of AARON
Sent: Friday, November 23, 2012
1:48 AM
To: korgpolyex@yahoogroups.com
Subject: [korgpolyex] Mods
complete (for now, anyway)
After thinking about it for a long time, I finally did
it. Or "them," to be more accurate. Within the last couple of weeks,
I've done mods to two of my Poly-800s: the Moog Slayer, 12/24 dB, FM-800, and
battery backup on one machine, and just the Moog Slayer on the other.
Obviously, these mods really open up the sound-making capabilities of these
machines. At first, I didn't understand what the FM-800 was capable of until I
did some reading. Then, once I figured it out, I was blown away with what it
can do, and really glad I did it.
The only other thing I'm thinking about doing is putting a knob on the front
panel to control the noise level (parameter 33). Has anyone done it?
Aaron