Electrician's advice wanted: safely lifting ground

Folks. I did contact the person who built/mod'd my amps and it was he who provided the solution based on my experiments to track it down. Once I opened both amps, the problem was clear. One amp was using wbt input connectors and had a connection between the ground rings and chassis ground. The other amp did not have such a ground connection. The are not mono-block amps, just two stereo amps bought from different people who chose different options as far as the input connectors are concerned. Things are still grounded through the power cords.

The cause is that the center taps on the transformers are not identical and you get a ground loop current between the amps when their inputs are connected together. Simple once I saw that one amp did one thing with input ground and the other didn't.

Not completely sure where I got the idea I originally posted about. Probably from reading forum posts. ;-) :-)

The danger from electric shock depends on several factors including but not limited to the persons own electrophysiology, the impedance of the person at the time, and the current path through the body. None of these depend on the potential. For example, an arm to arm path will result in more current flowing through the heart than most other paths and put you at more risk of vfib - not a fun thing. While a GFCI provides protection (in a different manner than a grounded chassis) the question to really ask is why are you using equipment that is so poorly designed that you have to lift the ground to avoid hum? And, no, hum is not unavoidable and "just part of the unique, wild and dangerous life of the audiophile." In short, there is no excuse or valid reason for placing yourself at any additional risk in this regard. Remember, there are those who in bygone days would use pennies rather than fuses in their panel. Just because something works (look ma, the lectrics on and ain't never gonna blow that penny, plus we done saved 14 cents on the fuse) doesn't mean its a good idea (darn ma, the house burnt down, with junior long with it - oh well, them's the breaks). Do not defeat safety grounding, don't smoke, use your seat belt, avoid crack - just common sense.

is why are you using equipment that is so poorly designed that you have to lift the ground to avoid hum?

Thanks for your opinion, but did you read my last two posts?

The only ground lifted is the chassis ground to the INPUT connectors. The chassis is still grounded at the power input to the amps. There is no safety issue with my solution.

Dan ed, your solutions is good only for components in which the input and output jacks are isolated from the chassis. I have seen few where there is such isolation.

Lifting the chassis ground is dangerous if there is a hot wire in contact with the chassis and you are grounded and can complete the circuit, such as being barefooted or touching the defective chassis and another grounded one.

My line stage only operates at it max if all other components have no ac ground but it does. Would Underwriters Labs take exception to this and deny certification to a manufacturer doing this? Yes. Would you city electric department? No. Do I feel unsafe? No.

Tbg,

IT is not the chassis ground! Chassis ground is intact, still there, grounding away, at the AC input. The inputs to both amps are grounded back to the preamp.

The lift is to the input connections ONLY, and they are tied to the power supply ground. Everything is grounded! Why doesn't it hum anymore?

One amp had an ADDITIONAL ground from the inputs to the chassis, one did not, simply due to different type of connectors.

Take a look at Rogue, Bryston, any other manufacturer that provides a ground lift. This is what they do also.