"Lloydj" <ljeffords@[EMAIL PROTECTED]
> wrote in message
news:1194559452.441751.97860@[EMAIL PROTECTED]
> Guys,
> We're installing our audio gear in London and on first power up the
> gear is humming like a demon. We were able to test our signal in the
> US before ****pping only as far as the amplifiers because they came
> hard-wired for 240V, and it was clean up to that point. We are
> connected to the building through rack power strips with appropriate
> UK plugs. The building is undergoing renovation so anything could be
> at work.
> It sounds like a typical bad ground condition, so I'm asking for those
> with experience in this realm to lend ideas on how to overcome this
> situation without lifting grounds, or a suitable testing means that
> would say the problem is the building ground itself. We've got
> computers involved and don't want to lose ground (earth).
> Thanks ever so,
> LJ
>
If possible run the FOH gear (mixer and accessories) from the same circuit
as the amplifiers. This works for me 99.9% of the time.
If this is not possible or practical install a good quality isolation
transformer in each 'send' (audio circuit to amps).
The transformer should have a 1:1 turns ratio but a DI (direct box) can
work
in a pinch DI boxes often use a 4:1 turns ratio however so your gain
staging
will be affected.
You may have to cut the audio ****elds at one end to resolve the issue.
This
in conjunction with the transformers may brake the ground loop.
Do a check with a cable tester or ohmmeter on each send. A miswired
connector can cause much grief.
Check the system with all stage lighting off. Dimmers can cause a lot of
hash on the power lines.
I'm assuming analog sends.
One other thing to watch out for: Hearing assist inductive loops can cause
hum in dynamic mics and pickups. Check to see if the venue has one of
these
and see if turning it off makes a difference.
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