Bad Hum Coming Through Amp, What Happened?
On the AC IEC inlet located on the component, I tape the grounding prong to block its connection to the power cord. This is the same as adding a cheater plug at the opposite end of the power cord, or pulling the grounding prong out of the IEC. I also have star grounding of all components from wires connected to the chasis, to the Tripoint Troy. Tripoint Troy is a RF/EMI filter that grounds everything through an outlet. |
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 |
Rtn1 and Almarg,I just want to be sure of the procedure in taping the ground post.When using a turntable do you connect the grounding lead from the turntable to the grounding post on the preamp and then wrap the grounding post with Electrical tape.This is the first time I have heard of this method to eliminate hum. |
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 |
Longshot and maybe some help....long term. Go to home multi-mart and get an outlet tester. Not one of the 'does it have voltage' types, but one which will show various hookup faults, including hot to neutral or ground reverse and various 'opens'. They are cheap and should be in anyones parts box who has any work done on there power. |
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 |
Ehaller, I took your advice first figuring that even if it wasn't the problem, it would at least be something to do as good maintenance (similar to tightening the screws on a chassis every so often). The toroidal transformer was tight, but after I took a wrench to it, I got about 2 whole revolutions to get that sucker in as tight as possible. After I turned on the unit, I found out that the buzz had gone down about 20%. Kudos to you for this suggestion! I still had 80% of the noise to deal with, so up next... Almarg, I stopped at Target on the way home and picked up a 2-pack of cheat plugs for $1.79, so now I tried adding these to the system. After I plugged the equipment back in and turned on the amp, I heard... SILENCE! Incredibly excited, I turned on the cd player and phono pre-amp, started the volume at zero, and turned it from 0-max on all of the inputs and heard, once again, SILENCE! All of my woes have been solved, thanks to everyone here for their opinions and help identifying the ground as the problem, and especially to Ehaller and Almarg for their ultimate solutions to the problem! Now to think that I spent money on a new AC receptacle, power cable, and power conditioner all in an effort to fix this problem, when it took $1.79 to eventually solve it. Oh well, they were upgrades I needed a push to do anyways... Thanks again, everyone! |
Out of the blue a couple of weeks ago, a nasty hum has started to emit from the amp through the speakers, audible starting at 20-25% of the volume output and louder as the volume increases.Ground loop hum as a rule is volume independent. Therefore jmho your problem is not related to a ground loop problem. The hum occurs whether the components are off, on, or in standby.Just for the hell of it unplug the source component from the power outlet. Is the hum still present? You said everything was fine up to about two weeks ago.... I would reset everything thing with your audio system back to the way it was before the problem started. I would also try plugging all the associated equipment directly into the wall power. Do not use the power conditioner. in fact unplug the power conditioner from the wall outlet. Primare I21 . |
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 |
