In reference to amps with a resistor between the circuit ground and chassis ground (usually with a parallel film cap to AC ground the circuit to the chassis), that resistor can be replaced with a inrush thermistor. That way the desired DC impedance between the chassis and circuit ground (it's there to monkey wrench ground currents) is maintained unless there is a fault. If that were to happen resistance drops allowing the breaker to trip. |
Thanks Al. I did just read this.....seems we have some cases of electrocution on record. We Aphiles should be aware.
" In the professional audio and video fields, the cheater plug has been identified as a serious safety problem. Its casual use as a method for avoiding ground loops in analog audio and video signals (to eliminate hums and buzzes) is dangerous.[4] Bill Whitlock, president of Jensen Transformers, writes, "never, ever use devices such as 3 to 2-prong AC plug adapters, a.k.a. 'ground lifters', to solve a noise problem!"[4] Whitlock relates how an electrical fault in one device that is connected to its electricity source through an ungrounded cheater plug will result in dangerous, high current flowing through audio or video cables. Whitlock notes that in 1997, consumer audio and video equipment electrocuted nine people.[4] |
01-03-15: Grannyring
If a power cord would have a short to the chassis would'nt that trip a breaker in the home? Hi Bill, The purpose of the AC safety ground connection (which is what a cheater plug defeats) is to make that happen. Since equipment having 3-prong power plugs connects AC safety ground (the cyclindrical third prong) to chassis, a short between AC "hot" and chassis will cause a very large current to flow through the circuit breaker, resulting in the circuit breaker tripping. If the AC safety ground connection is defeated with a cheater and that kind of a fault occurs, what is likely to happen is that the 120 volts will cause a current to flow through the shield and/or the return conductor of an interconnect cable to another component, and through that component's AC safety ground back to the service panel. However, depending on the design of the grounding configuration within each of the components a significant impedance, perhaps 10 or 20 ohms or more, will often exist (and should exist, if the equipment is well designed) between the circuit ground and the chassis ground/AC safety ground of each of the components. Chances are good that that resistance will be high enough to reduce the current flow to an amount that is too small to cause the breaker to trip. In that situation what is likely to happen is that the interconnect cable will get very hot, creating the possibility that it might either go up in flames or ignite whatever it may be in contact with, such as a carpet. And of course the chassis would present a shock hazard to anyone who touched it. Al, most amps are grounded at the first reservoir cap in the power supply etc... That doesn't change what I have said, as that involves the amp's circuit ground, not AC safety ground. BTW, I should add to my earlier mention of ways in which AC "hot" can become shorted to chassis the possibility of a short developing in the power transformer of a component. ... it will at least help you understand if it is a ground loop issue. Agreed. Using a cheater plug temporarily as a diagnostic tool can be useful, and entail negligible risk. It is also reasonable to say many things we do every day are far more risky. Things like riding a bike, taking a walk, ice fishing, etc... Agreed. But it is each individual's call. My point, though, is that a statement that using a cheater is "completely safe" is misleading and incorrect. Best regards, -- Al |
If a power cord would have a short to the chassis would'nt that trip a
breaker in the home? I think the most cautious of us would say never use
them as there is certainly a possibility of shock if all the conditions are
aligned perfectly. It is also reasonable to say many things we do every day
are far more risky. Things like riding a bike, taking a walk, ice fishing, etc...
I did just read this ...............
"In the professional audio and video fields, the cheater plug has been
identified as a serious safety problem. Its casual use as a method for
avoiding ground loops in analog audio and video signals (to eliminate hums
and buzzes) is dangerous.[4] Bill Whitlock, president of Jensen
Transformers, writes, "never, ever use devices such as 3 to 2-prong AC
plug adapters, a.k.a. 'ground lifters', to solve a noise problem!"[4] Whitlock
relates how an electrical fault in one device that is connected to its
electricity source through an ungrounded cheater plug will result in
dangerous, high current flowing through audio or video cables. Whitlo |
Goodness I have used cheaters my whole 37 years of audio life. Most of us have and it will at least help you understand if it is a ground loop issue.
I must be lucky:). I have never, ever heard of any incident in real life to be honest Agoners.
Al, most amps are grounded at the first reservoir cap in the power supply etc...
This topic comes up all the time on many threads and it always makes me think " who has ever, ever been harmed by using a cheater on an amp or preamp?" |
Not to harp on this, but electricity will try to find the shortest/easiest path to ground. By removing that short, certain path by lifting the ground, and a fault occurs, "You", your family touching something else, your pet, or other equipment may become the shortest/easiest path to ground instead.
Be safe, be smart, don't take things for granted. |
01-02-15: Bojack
Using cheater plugs is completely safe and often effective. Don't let the underwriter of your homeowner's policy see that post :-) Assuming the equipment is in good physical condition, so that there is little risk of an internal short developing between a "hot" AC wire and chassis, the risk that is entailed by the use of a cheater plug is extremely small. However, it cannot be said that the risk is zero. And if that very small risk were to ever materialize, perhaps because the component was marginally designed with respect to how the internal AC wiring is routed relative to nearby sources of heat within the component, or perhaps because the component was wired on a Friday afternoon by someone who was in a hurry to leave, or for whatever reason, the result could very conceivably be either a fire or electrocution. Yes, use of a cheater plug is "often effective." However the third prong is provided on AC plugs and outlets for a reason. A claim that use of a cheater plug is "completely safe" is, frankly, misleading, potentially harmful, and nonsense. Good comments by the others. Regards, -- Al |
No disrespect Bojack but that statement is completely untrue, irresponsible and ignores why the ground was there in the first place.
Again, find and fix the problem. Using a cheater plug may mask a ground loop problem, but causes greater concerns by lifting an important safety element in the home's protection and placing your home, equipment, family, etc. at risk. |
Using cheater plugs is completely safe and often effective. |
Ground Loops and hum have been the source of many discussion hear on Audiogon. I would suggest that you do a search of ground loops and hum and read a few.
That said, ground loops can be caused by several things.
1. Poorly designed and constructed equipment with insufficient grounding schemes. This is the hardest to fix because the item itself is badly designed.
2. noise generated by home items such as lights, refrigerators, motors, etc.
3. poor interconnects, where the return and shield are connected.
4. Poor electrical connections where neutrals are shared by other lines. This happens a lot.
5. Poor electrical connections of the audio components.
As was mentioned previously, you must first find the source of the problem in your system.
The best way is to unplug and disconnect all the components except the amplifiers and speakers and then turn the amps and speakers on. Noise? no? Then move on to the next section. Noise? yes? Then it is the amps.
Connect the active crossover (if you have one), if not connect the pre-amp to the amp(s). Make sure all other components are unplugged and disconnected (interconnect cables) and only the crossover or pre-amp, amp and speakers are connected. Noise? yes, then it is the crossover (if you have one), interconnect cables, or pre-amp. No noise? Then move on.
connect a source component to the pre-amp and plug it into. pre-amp, amp and speakers are still connected. Noise? yes, then it is the source component or interconnect cables. No? then it is another source component that plugs into the pre-amp and test those.
Also, and very important to lower the noise floor extremely and to help eliminate ground loops are dedicated lines and proper connection of low level components.
I always advocate at least three dedicated lines. More depending on what you have. Two dedicated lines. One for each amp and one additional dedicated line for all of my low level source components. My low level source components (pre-amp, active crossover, tuner, cd transport, DAC, turntable) are all plugged into a power conditioner ( I really like the Transparent Audio Power Isolator 8 unit) which is in turn plugged into its own dedicated line. This helps eliminate ground loops.
The problem arises when your system is sharing a line with other stuff in your house before the electrical panel, such as the lights, and refrigerated.
Also, a dedicated line is as follows: A hot, neutral and ground wire "dedicated" solely for the one pair of outlets, which all three together go to the electrical panel and the neutral is not shared.
12 gauge or 10 gauge "romex" with hot, neutral and ground per line to the panel.
I had a ground loop the other day only to discover that I had accidentally plugged one component's power cord into the same outlet as my low level components connection. When I corrected this by plugging it into its own dedicated line (as it was supposed to be), the ground loop disappeared.
You don't need cheater plugs to find the source of a ground loop. Just follow the instructions above. People use cheater plugs to "fix" the ground loop and that is not the proper way to go. It is totally unsafe and being in the power/electrical field, is really......stupid. Once you discover the cause of the ground loop. Fix the problem.
enjoy |
I had a hum caused by me Eastern Electric MiniMax DAC Plus when I added it to my system. I used an Ebtech Hum-X with it and the hum went way. I got the Ebtech Hum-X from Guitar Center on sale during the holidays. It is a safe cheater plug that can handle up to 6 amps of current.
Like others have stated start at the preamp and sources first. |
Thanks for the info. One more question. If there is a hum generated from a ground loop would it be there say at the end of a song or between tracks when listening to the CDP? |
Based on my own personal experience, hum can also be picked up as airborne EMF from a nearby amplifier. In my case, what I had spent hours configuring and re-configuring, as suggested by Tjassoc, was not an AC ground loop at all, but EMF picked up by my IC connecting the phono stage and pre-amp. Simple aluminum foil around the IC remediated the problem. This issue can be very tricky, as my own experience attests to. Good luck. |
You should be very careful when using "cheater" plugs or removing the ground prong on a plug.
Equipment ground is there for your safety, removing it eliminates electricity having a safe path to ground.
Solving the source of your problem - a difference in potential with the different grounds in your system - is the best way to solve the problem.
Try using a single circuit. If that's not practical, try using a single circuit for your amplifiers and another single circuit for your source components.
If this doesn't work, you'll need to identify the source of the hum. Unplug a single component, one at a time, to see if it removes the hum - trying the preamp last.
Once you find the source(s), try plugging them into a circuit common with other parts of the system. Say a transport is the problem and it's plugged in a separate circuit, try plugging it in with the rest of your source components, or your amplifier(s) - in that order.
If all your equipment is plugged into a common circuit, than your equipment is suspect and it is NOT recommended to remove the ground prong of the plug.
Good luck and hope this helps. |
Try one at a time starting with preamp
Alan |
