Bad Hum Coming Through Amp, What Happened?

See my response to your other post.

I wouldn't think the problem is in the output stages, because of the sensitivity to volume control setting and source selection, even when the source components are turned off and sending no signal into the amplifier. It's most likely a grounding problem (for which I suggested some things to try), or an internal problem in the input selection or other front end circuitry of the amplifier.

Regards,
-- Al

I have used those ground cheater plugs before & they work great. Does anyone know the downside of using them if any?

Aside from the additional contacts which are introduced into the ac path (which could be eliminated by following Rtn1's suggestion), I think that the one downside would be the fact that the safety benefit of having a safety ground on each piece of equipment is lost.

However, assuming that at least one piece of equipment in the system does not have its safety ground defeated, and that should generally be the preamp or integrated amp, the chances of a problem resulting would seem to be extremely remote. The only scenarios I can envision where a problem would result are:

1)A piece of equipment that is being connected into the system is plugged into the wall through a cheater plug, before the interconnects to the rest of the system are connected. That component has an internal short which causes its chassis to be electrically "hot" (i.e., at 120vac potential). The user connects an interconnect cable to it, and then simultaneously holds the shell of the rca connector at the other end of the cable in one hand while touching the chassis of a grounded component with the other hand. He will receive a shock. Or, similarly, the user plugs a component with a hot chassis into the wall before connecting it into the system, and simultaneously touches its chassis and some grounded object.

2)A component with its safety ground defeated develops an internal short causing its chassis to become electrically hot. All of the interconnects (probably two, for left and right) between that component and the rest of the system are defective in such a way that their shields have an abnormally high resistance (say 10 ohms), but the shields are not completely open. High levels of ac current would be conducted through them, that would cause them to overheat but would not be sufficient to cause the circuit breaker to trip.

As I say, the scenarios in which a problem would result are pretty far-fetched.

Regards,
-- Al

Rtn1, my Sunfire poweramp has 2-prong connector and everytime I try to touch any of my equipment pieces I grab a great piece of the static charge especially during the dry seasons or winter when heater is always on. So figure to have the same with cheater plugs.

As long as at least one of the interconnected components has its safety ground connected, the chassis of all of the components will be at ground potential. So the static discharge you feel would be due to the static voltage on your own body discharging to ground (static buildup being at its worst in dry wintertime conditions, and especially if you have been walking on carpeted surfaces). The same thing would happen whether or not cheater plugs were used on some components, as long as at least one component has a 3-prong plug which is not defeated.

If no components have 3-prong plugs, or if the safety ground is defeated on all components (which are situations that should be avoided, as I indicated above), then the chassis can "float" to substantial voltages which could cause a shock (typically a mild one).

Regards,
-- Al

Goldeneraguy -- No, don't use any tape at all on that connection. We were referring to power cords only (and isolating the safety ground of the ac wiring from the component's ac power connector), not to the ground connection between turntable and preamp. Defeating the connection of turntable ground wire to preamp ground post will most probably increase hum significantly.

Regards,
-- Al