Grounding ?

---> Bob,
why relying on grounding through mass of interconnect cables is bad idea?

I have preamp and two monoblocks - all with unbalanced connection only. Ground is connected to the chassis internally. I have mains cord grounded only in preamplifier. Both monoblocks have lifted ground in power cords and are grounded through interconnects and preamplifier's power cord.
All hum disappeared and such connection seems to be safe (monoblocks are grounded through preamp). What is wrong in such approach?

Shock risk; possible inadequate wire size when ICs serve as ground; noise from having ground current flowing through ICs.

(1) If the amp should develop a problem that puts live AC on the chassis, the fault current will be flowing through the IC. Depending on the level of the fault, it may not be enough to trip a circuit breaker, but still be enough to electrocute you (all it takes to stop your heart is a few mA of current). You could be electrocuted from coming into contact with one end of an unplugged IC and chassis of the amp or other component connected to it.

(2) The shield/ground wire size in an IC may not be of a size adequate enough to carry full ground fault current, which can be greater than normal.

(3) Small ground currents flowing through ICs can create the very noise you're attempting to solve by lifting ground in the first place.

Thank you for the answer.
So, what is a solution?
Is the isolation transformers like Jensen Transformers are the only solution for full unbalanced system?
Honestly I do not know any person who use it.

Is a possible fix, and this is JUST a question, that 1 or more pieces has an internal hot/neutral swap?
Could you tell somehow? Maybe have all gear plugged into the wall without any I/Cs. Than measure for voltage between the chassis or ground of each piece? If there is a voltage between chassis of 2 pieces, isn't that a hot/ neutral swap?

Does everyone own an outlet tester? The type w/3 leds to indicate various good / bad conditions?

Which raises another question, why do some amp manufacturers include a ground lift switch. The answer is very simple because they know it can be very convenient to flip a switch to lift the ground to avoid hum caused by a ground loop rather than buy and use a sound degrading cheater plug or cutting the ground pin off the power cord.

Note: When using some tube preamps, I have had to lift all the grounds on all components except for the preamp to eliminate hum or considerably reduce it. The other thing to check is to make sure all power cords are not too close to the interconnects.

Mike Elliot talks extensively about ground loops and hum on his Alta Vista website and recommends all except one component be grounded and if a ground fault occurs in any system component it can be safely drawn away by the interconnects via the one grounded component. I think we can trust this excellent designer who has been producing quality gear for many years.