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Refurb VS Replace P6 Power Supply - strange high pitch issue

2014-10-27 by jim@saltlands.com

Obviously cost is the idea behind this, but just wondering if a simple recap or power supply section would help with noise.. AND also help to eliminate a partiular minor problem i have…

Every once in a while, if I"m playing in one register (upper/lower, etc) and hit a note that's drastically in the other register, a tiny high pitch (5K maybe?) comes in, albeit at low volume, with the note and stays until i hit another note. Well, usually it goes away upon the next note, but occasionally it stays if i remain in the same register.

It's almost like the instrument is reacting to the extreme frequency change.

It doesn't apply to a particular voice, as i've tested this out with the board open and watched the voicing to see. It just happens every once in a while, and on no particular voice.

I've had random unexplainable high pitches like this be eliminated from other equipment, mostly mixers, by addressing the power supply to some capacity. Once it was a full replacement, other times just a recap.

Anyone have any thoughts on this kind of thing?

Re: [PolySix] Refurb VS Replace P6 Power Supply - strange high pitch issue

2014-10-28 by Chromatest J. Pantsmaker

A recap could never hurt... Do the calibration after.

On Mon, Oct 27, 2014 at 1:19 PM, jim@saltlands.com [PolySix] <PolySix@yahoogroups.com> wrote:

Obviously cost is the idea behind this, but just wondering if a simple recap or power supply section would help with noise.. AND also help to eliminate a partiular minor problem i have…

Every once in a while, if I"m playing in one register (upper/lower, etc) and hit a note that's drastically in the other register, a tiny high pitch (5K maybe?) comes in, albeit at low volume, with the note and stays until i hit another note. Well, usually it goes away upon the next note, but occasionally it stays if i remain in the same register.
It's almost like the instrument is reacting to the extreme frequency change.

It doesn't apply to a particular voice, as i've tested this out with the board open and watched the voicing to see. It just happens every once in a while, and on no particular voice.

I've had random unexplainable high pitches like this be eliminated from other equipment, mostly mixers, by addressing the power supply to some capacity. Once it was a full replacement, other times just a recap.

Anyone have any thoughts on this kind of thing?

Re: [PolySix] Refurb VS Replace P6 Power Supply - strange high pitch issue

2014-10-28 by jim@saltlands.com

here at old crow's site, http://www.oldcrows.net/~oldcrow/synth/tips.txt he discusses at pretty good length the importance of various capacitor purposes within synthesizers, particularly decoupling capacitors. For those he mentions that many synths have a plethora of .1uF caps all around circuits, and that they serve to keep a lot of noise out, such as high frequency noise.

In the polysix circuits, there are lots of .01uF, not .1uF. I'm not familiar yet enough with circuit theory to say wether or not those are the decoupling caps for the polysix. Can someone tell me?

My high pitch (and i call it pitch because it's audio range) noise that happens once in a while, is seeming likely to me to be a cap issue somewhere. I'm hesitant to start recapping things without having more of a target. Though i suppose it couldn't hurt to do the two big power ones and the five or six other small ones that are on the same power board.

Re: [PolySix] Refurb VS Replace P6 Power Supply - strange high pitch issue

2014-10-28 by Chromatest J. Pantsmaker

You'll see decoupling caps (the values can vary) right around the ICs. If you have a noisy power supply, you're arsed to begin with. An incredible range of problems can be solved by fixing a power supply (in all equipment, not just the P6 specifically).

https://learn.sparkfun.com/tutorials/capacitors/application-examples

On Mon, Oct 27, 2014 at 10:42 PM, jim@saltlands.com [PolySix] <PolySix@yahoogroups.com> wrote:
tty good length the importance of various capacitor purposes within synthesizers, particularly decoupling capacitors. For those he mentions that many synths have a plethora of .1uF caps all around circuits, and that they serve to keep a lot of noise out, such as high frequency noise.
In the polysix circuits, there are lots of .01uF, not .1uF. I'm not familiar yet enough with circuit theory to say wether or not those are the decoupling caps for the polysix. Can someone tell me?