Funny, I never saw this thread. Search seems not to be terribly reliable in highlighting all threads.
Anyway, let me clarify a few things since there are some inaccurate assumptions being made.
1. There should be no noise when rotating controls with no signal present. Any noise that can be heard is generally the result of a microscopic oxide or contaminate on the surface of the resistive element (lots of this is environmental depending on where in the country or world you live) and generally a very tiny amount of Caig D-5 sprayed inside the control (really, a tiny amount is all you need, more can cause other problems) will solve this permanently. The D-5 breaks this contaminate and coats the element with a conductive microscopicly thin protective film. If this does not solve the problem, the control must be replaced. Do not use anything other than Caig D-5, most other products that appear to be the same do not work well and many will damage the control's element and severely reduce it's lifespan. In this case, all of the controls will need to be replaced.
2. With signal present, there may be some noise when turning the controls (specifically the gain and volume controls) because of microscopic bumps that cause the gain to change in audible variations. What you are hearing is the instantaneous step changes, and with a bass signal these are harmonics that are much more audible. If you were to use full range music, the masking effect of the higher frequency program would mask most of this. Detented controls show this effect more than smooth controls because of the mechanical transmission of the detent through the wiper and element. The best fix for this is also a tiny spray of Caig D-5 into the controls, but it works for a different reason by lubricating the wiper element as it's contact surface passes over the microscopic surface. Generally, this problem gets BETTER with use, as the wiper and element burnish smooth.
3. Effects return jack's internal normalling switch is another, entirely different issue that is responsible for intermittent signal with all manufacturer's products that use this signal routing option. Since the switches are open, they are subject to dirt, dust, spider web (yes, spiders seem to like these jack holes a lot), and environmental corrosion (especially those of you in marine environments). This also is best cleaned with Caig DeOxit D-5. On our amps, the orientation of the jacks are such that you need to turn the amp upside down and spray a small amount into the jack and cycle the jack with a plug. The only jacks that need this would be the return jacks, the send jacks do not have the switch used.
Hope this helps clarify, and avoid any costly misapplication of otherwise well intended advice.
