Suppose a pot...

[boratto]

Suppose a pot, 100k, and it´s noisy as hell, but it just happens on last 5% of rotation.
First 95% was heaven.

lug1 - circuit
lug2 -input signal
lug3 - circuit

what to do to tame this thing??

[IvIark]

At the end of the day, a pot is just a resistive track with the wiper making a mechanical contact with it along the rotation.  These things aren't mechanically perfect, and so if at any point of the rotation the track is imperfect or uneven, then there's every chance that will translate into a poor connection and noise.  So having a slightly defective pot is always possible.  What circuit are you talking about and which pot?

[boratto]

Mark it´s the Intensity pot of Hyperion (v1)!

[IvIark]

And what sort of noise is it, is it a scratchy type of noise, or oscillation or something else?

[boratto]

it´s scratchy...it´s not an oscillation.

[IvIark]

Sounds like the pot then.  I'd try another and see if that sorts it out

[boratto]

same thing on another 100k, and using a 50k, the noise start at 80% instead 95%. Seems like excessive effect (intensity)... i was thinking on how to tame a bit the intensity.

[IvIark]

Well you could put a resistor in series with the scratchy lug in between the lug and board, but it shouldn't happen so you'd be better tracing the problem to the source.  Is the transistor socketed?  May be worth changing that

[boratto]

i will build a new one with scoketed transistors and swap all 100n multilayer capacitors for poliester ones... and then, if it becomes noisey again i will put a resistor (thanks for the tip). I´ll will update the results here, maybe next week.

[Jopn]

Definitely worth double checking your board as well.  If that pot is somehow affecting the voltage bias of the transistors (which it shouldn't in that effect) you'd get scratching/crackling sounds.

It's a small board, so a quick reflow, track cut and double check of the cut traces should only take a few minutes.