I've also tried the other channels, and get the same performance and noise from each one. (I've also reduced the frequency down to 100 to make sure I get 4 channels) - and I'm using the int osc to compare it against the 12F

I've noticed that the growling from the armature has a second resonating sound that I can only describe as the sound you get with a multi-engine prop plane when the engine is slightly out of sync. I can only assume this is due to the PIC having to work hard outputing to 4 channels rather than the 1 on the 12F.

If all else fails, I'll use a 12F675's to drive each of the 4 controllers... overkill I know, but the performance I was getting with the 12F was just what I was after.

I'm hoping the issue with the 16F676 is due to a conflict of configuring the ports to the correct analogue / a2d / digital combination, and with your help, will work as good as the 12F !