Clicks 'n pops

[Shane]

Sorry to sound ignorant, but what is the function of earth lift? Why aren't all earths taken directly back to mains earth?

[Little Mick]

HI

To reduce hum via loops, I have always wondered about its safety haply someone might explain

Regards

[Dave the bass]

Originally Posted by Little Mick

HI

To reduce hum via loops, I have always wondered about its safety haply someone might explain

Regards

Yup, I had an 'earth lift' on a huge great Valve Bass guitar amp I sied to gig with. At bigger venues when it was DI'd (Direct Injected) via XLR through the front of house PA system we'd get an occasional buzz. Flicking the switch got rid of it.

I never got a belt from anything mind. Lucky?

DTB

[Stratmangler]

Originally Posted by Dave the bass

Yup, I had an 'earth lift' on a huge great Valve Bass guitar amp I sied to gig with. At bigger venues when it was DI'd (Direct Injected) via XLR through the front of house PA system we'd get an occasional buzz. Flicking the switch got rid of it.

I never got a belt from anything mind. Lucky?

DTB

The "earth lift" switch was there to remove the chassis ground of one or other device from a ground of different potential to that of the man PA rig. You were earthed via the XLR lead, therefore safe. If you weren't earthed at all you would have had [i]serious[i] buzzing going on (bag of angry hornets comes to mind).

I have had a belt off earth connections of differing potentials, and whilst not in the dangerous (as in life threatening) category, it was not pleasant.

Chris

[Richard]

Yes, electricity, including any circulating earth currents, takes the path of least resistance. By putting a resistance between mains earth and system ground (which is just a reference for the circuit and can be separate from mains earth) we stop the currents circulating through the circuit and causing hum.

Mick, this is quite safe to do so long as the case and any other external metalwork is solidly bonded to mains earth. Whatever then happens to the circuit, or touches the case, is earthed to the mains rather than you.

Rich

[david]

My five pin Binder plugs, sockets and cable arrived and I installed them on snowy Sunday as follows: chassis of Pre and output tx screens connected direct to the earth connection. Mono’ed earth connections connected back to common earth point on psu cap. This common earth point is then connected to the negative connection on the power socket. I’m happy to report that this has totally cured my hum problem, and also completely stopped the Pre 3 picking up clicks and pops from light switches, central heating etc.
It sounds a tad more airy too, but that may just be the removal of the background hum component!
David