Re: hum when biamping -- ground loop or interference?

"Mike Rieves" <mriev@xxxxxxxxxxx> wrote in
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"The BorgMan" <me@xxxxxx> wrote in message
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"Mike Rieves" <mriev@xxxxxxxxxxx> wrote in
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"Derek Tearne" <derek@xxxxxxxxx> wrote in message
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Mike Rieves <mriev@xxxxxxxxxxx> wrote:

Where in hell did you get the idea that I said to "lift the
ground"!?!
Maybe you should go back and re-read my posts.

From your original post: The simplest method is probably to use a
three prong to two prong ac plug adapter on one amp, that will lift
the ground on one amp, and that should cure your ground loop.

That's where you said it. It was wrong there, and is still wrong.

--- Derek


No, you're wrong, leaving one amp grounded to the AC line means that
both amps are still grounded through the connecting cables. The
cable sheilds will carry any minor fault current to ground and a
major fault will cause the AC circuit breakers to blow. Assuming
that one has enough sense to check the AC outlets for faults in any
new venue, there is no risk of electrical shock or equipment damage.
If certain types of AC faults exist, there will be risk of shock or
equipment damage, whether both amps are grounded or not. Lifting the
ground on one of two or more connected pieces of equipment poses no
extra risk as long as at least one is grounded.




Problems:

1) Assuming chassis ground and signal ground are connected.
2) Assuming instrument cable can handle fault current, or fail before
killing someone


1) if chassis ground and signal ground are not connected, there is no
risk of a ground fault causing a dangerous voltage on the signal
ground.

Yes, and if wired up in the manner you propose - the chassis is now hot
becuase it has no ground connection.

I don't want the chassis, or the cables to be hot.

2) Take a good look at the shield braid on a decent instrument
cable, you'll note that it usually about as heavy as the ground wire
on most audio equipment.

....and 5 times as long, and likely not as conductive, with much worse
connections at either end, and possible one end or the other not
connected...

--
Aaron
.

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