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Hi, I had a ground loop hum problem with a new Ming DA 2A3 preamp I just received. The first thing I tried was a Home Depot cheater plug to defeat
the ground on the preamp. It worked fine, problem solved. I just don't like the idea of my $2700 preamp power cord (Stealth Dream) plugged into
a two dollar cheater plug. It would be great if Oyaide or Furutech offered an audiophile grade cheater plug. Of course, it would be even better to solve the ground loop hum problem without the use of a cheater plug. Does anyone know if there is a high quality cheater plug on the market? How about advice on solving the problem without using the cheater plug? Thanks.
Bart
Follow Ups:
Because I have a case of Coopers and I want to use them up. All three of my vacs had chewed up/bent blades.
If you buy a plug to make a cheater, just make sure you mark it somehow so you know the hot and neutral are reversed.
If you try one of those Ace Hardware cheaters and discover that reversal does in fact reduce the hum, it might be better to reverse the wiring inside your amp.
Using the cheapo cheater is also a good time to test the orientation which provides the least on chassis voltage, using the volt scale and connecting the red (+) lead to the chassis and the black (-) lead to ground (the third lug) at your outlet.
doggy
I continue to use only my preamp grounded. It sounds much superior. I use all Dream power cords.
You might want to check this out. It is a cheater plug unless the voltage on the ground gets above .6 volts.
http://www.zzounds.com/item--EBTHUMX
Bart-
All good suggestions to research to properly manage the ground loop issue.
Probably an obvious issue that may not even be relevant is if you have a cable TV coax coming into the room and on the circuit anywhere?
There are easy safe fixes if that is causing the problem.
I would also second the Alan Maher PE units as an alternative or in conjunction with the chokes.
Good luck.
The ground loop injects hum if there is some source of 60 Hz voltage in the AC safety-earth wiring. If you have a complicated AC wiring scheme, try stripping it out and powering everything from a simple power strip to see if the hum goes away without the use of the cheater plug.
If there is still hum, then disconnect all interconnect cables and measure the AC voltages between component chassis and audio ground (RCA shell) points, and each of these to AC safety-earth. It is likely that one component has an offset, and breaking the internal connection of audio ground to chassis will cure the hum problem. Some audio equipment includes a "ground lift" switch to do this: it does not disconnect chassis from AC safety-earth, but breaks the tie between internal audio ground and AC safety-earth for cases like yours.
If this still fails to point to the cause or remedy the hum, consider installing isolation audio transformers in either the preamp or the power amp.
There are no cheater plugs. What you are using is a ground adapter, meant to provide a proper AC safety-earth connection in an older house with two-port AC outlets. Anyone who sold a cheater plug would be liable for major damages, and you are placing your life at risk by using an adapter as a cheater.
If you were to go into Home Depot and ask for a ground adapter, you would get no information. Ask for a cheater plug and you might be told to go to the electrical department.
I am surprised that you don't recommend the diode device from Ebtech. Of course at $50 it is more expensive than the cheaters.
I don't understand (economically) why you're using a $2700 power cord on a $1200 preamp. I too of course would connect my best power cord on hand to my pre and sources too...I seem to think one that can afford a $2700 power cord could afford a $10K preamp. Anyway, I challenge anyone here to tell us their horrific personal experience from lifting ground. "Theory" and "reality" don't always intersect. How on earth did we not burn down at least every other house in the 30's,40's,50's and 60's when no homes had 3 prong grounded AC. There are companies that sell nice powercords without a ground. I also understand why you wouldn't just want to take a pair of pliers to it and remove the ground pin. Good luck!
ET
I've got the scars to show what that causes.
The third wire (AC safety-earth, aka "ground") in the present USA domestic wiring scheme is there to keep a faulty appliance from killing someone. Appliance manufacturers have the choice of making their products with two or three power wires. A two-wire appliance is "double-insulated," which means there is adequate internal insulation to keep any conceivable internal fault from bringing the user into contact with the hot wire. A double-insulated appliance such as a hair dryer can still be lethal if dropped into a bathtub, which is why we also have ground-fault interrupters on AC outlets near plumbing fixtures required by code.
Unfortunately for audiophiles, most fancy gear is made with three-wire power cords. The ground loop is the circuit connecting amplifier audio ground to source audio ground through both the interconnect cable ground as well as the AC safety-earth wiring. Hum results if there is any voltage generated within the safety-earth wiring, as it appears in series with the audio signal as far as the amplifier is concerned. Lifting the AC safety-earth connection with a cheater plug breaks that side of the audio ground loop, and cures the hum problem. However, it removes the safety aspect of the equipment design.
How dangerous is this? It is difficult for users to evaluate their risk in defeating a safety measure that only functions rarely. How likely is a party guest or child to spill liquid into your equipment? How likely is your equipment to contain a design blunder, that causes equipment to fail after a long period of use? I've owned four solid-state amps in my life, and one had such a blunder, so my guess is 25%. What is yours?
Awe-d-o-file, this $1200 preamp has outperformed my previously used (CAT Ult MK2) $6000 preamp by a wide margin. Another audiophile recommended it. This $1200 preamp replaced his $14000 (VTL 7.5) preamp. That's why a
$2700 (Stealth Dream) is used on it. Alan could you give me more details
on your suggestion? What transformer should I use? How do I install it?
Give me the "transformer installation to eliminate ground hum for dummies" version. Thanks. BTW I installed my first Hammond 193L choke on the PLC (Hydra 8) as you and Bartc advised. I ordered 3 more so I can install one for each used outlet on the PLC. I read a lot of your posts regarding this and assume I am donig this right. Am I? Also another basic question on connecting the Hammond 193L to the AC plug. I know the longer lead is the hot and the shorter is the neutral. I read on another post that said the hot lead should be attached to the wider blade on the plug and the neutral to the other blade. Is this correct? Thanks.
Bart
The wider blade is the neutral side of the outlet...make sure the hot wires into the right side of the outlet / ac plug orientation.
Alan
also, if you like the Hammond Chokes you may want to contact Alan Maher and talk to him about the Power Enhancers. I have several in my system right now (with no chokes) and these things work quite well. I'll be removing my PLC shortly as Alan recommended to see what the PEs can do on their own.
Hi clio09,
I am using a Ming DA 2A3 preamp and it is very good. How do I contact Alan Maher and where did you buy the PE's? Have you tried the chokes?
I have too many new variables in my system right now to tell how they are individually affecting the sound. Once the pre breaks in and I get an idea of where I am I'll start adding more chokes and see how they sound.
Bart
You can just e-mail me at: audionutge@yahoo.com
Alan Maher
Bart
Why would you want to lift the ground? This is a very dangerous idea...god forbid you have a surge or a short while you're touching the component. A better suggestion is to isolate the component using a medical grade isolation transformer with the center shield. This concept will break the neutral from the house and eliminate the hum, while maintaining the earth ground.
Alan
Yes,
Just take a high grade audio three prong connector and cut off the ground. Attach it to the male end of the $5.33 extension cord you want to cheat with.
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