ground loop

"Hi to all

Can you please explain what exactly is the ground loop?
I am trying to eliminate the hum between foreplay 3 and VTA st70

cheers"

I believe it is when you have currents flowing from your amp to your preamp or vice versa through the grounding connections.
When two or more devices are connected to a common ground through different paths, a ground loop occurs.

"Ground loop" is often used as a generic description of a condition where local ground references within a system are at different potentials. In my experience they are easier to describe then to eliminate. A common case would be a piece of equipment grounded via its power cord and also grounded to another piece of equipment via the shield of an RCA cable. If the two ground references are at different potentials you have a loop.

"A common case would be a piece of equipment grounded via its power cord and also grounded to another piece of equipment via the shield of an RCA cable".
Is this to say a non grounded component could be effectively grounded through the shield to the other grounded component? IE non grounded Dynaco amp through RCA cable shield to grounded preamp.

Pooch wrote: "A common case would be a piece of equipment grounded via its power cord and also grounded to another piece of equipment via the shield of an RCA cable".
Is this to say a non grounded component could be effectively grounded through the shield to the other grounded component? IE non grounded Dynaco amp through RCA cable shield to grounded preamp.

The outer conductor of an RCA jack is often tied to the chassis of the component in which it is installed. The chassis often represents a local ground reference. Assuming two components are connected via a standard RCA cable where one component is grounded (e.g. via three prong mains plug) and the second component features a two prong mains plug, yes, the shield of the RCA cable can provide a ground path for the second component. NOTE: Some RCA cables are "directional" meaning the shield is grounded at the source end but floating at the destination end. In that case the second component would not have a path to ground through the RCA cable. Make sense?
...j

This is a pretty good outline of how this is caused and fixed...

http://www.lh-electric.4t.com/gnd_loop.htm

great links, here is another one: http://www.equitech.com/articles/enigma.html