Sent Wed, May 1st 2013, 22:47
I have been looking into the P6 noise issue as part of my Kiwisix upgrade and I have managed to quieten the P6 by about 80% by adding some grounding wires. The ground layout on the boards is very poor and this is especially so on the FX board which is where most of the noise comes from. Unmodified the FX board is very prone to airborne interference and running very close to it and also the full length of it are the keyboard scanning wires which are pretty good transmitters as they are switched on and off at high speed. The Kiwisix upgrade actually made the noise worse as I am scanning everything much faster than the original P6. I have detailed in the user manual install section where to add extra grounds and in addition to these you also need to isolate the keyboard mounting leg that is touching the grounding foil that runs under the FX board. This is best done but cutting out a square in the foil. Even the power supply board is badly grounded and the power ground wires are too light. The best place to run the extra grounds from would be the ground leg of one of the large caps. MH like Dave already said, the Polysix cannot be used without a noise gate, or just you sitting at your desk and riding the fader. When it's playing, the Polysix really takes offense at any other synths. You can't use it with other harmonies playing in the mix; it almost always needs to be the only synth playing, other than a simple bass line, and unpitched drums. If you want a BD then it needs to be at the same pitch as the bass line, and you most likely need to put the P6 through a high-pass filter (use your EQ's low-reject). So what you want to do is to create holes in your melody when there's nothing playing (no reverb tails either), absolutely mute everything, then unmute the P6 and give it its time. Then mute that and unmute the rest of the track. That's taking it to an extreme but works well. Put a track compressor (maybe 10ms attack and 100ms release, 1:4) before the muting for a less visible sound or after the muting (with shorter release) for a punchier sound.