Apple Logic Pro /LogicExpress Discussion

From: james page <jimmymio@...>

>Just to clarify, XLRs, unless they have been modified
>which is very unlikely, are balanced so I din't think
>they contribute to your hum problem.  JP

I missed the beginning of this thread, but you should be able to get 
rid of the hum even if the runs to your Tannoys were unbalanced. And 
I assume you're talking about electrical hum, not acoustic hum (i.e. 
not a vibrating power supply). I also assume that the hum stops when 
you turn off the computer monitor, right?

First try moving the monitors away from the speakers (or just try one 
first). If the hum goes away, the solution is (pick one): buy an LCD 
monitor to replace your CRT; move your speakers farther away from the 
monitor (which is hard to do, of course); get rid of these speakers 
and buy some that are AV-shielded; or pay more than these speakers 
are worth to have them shielded.

Somehow the LCD monitor seems the most practical answer. :)

If it's not just a case of the monitor's proximity to the speakers - 
and usually the problem with un-AV-shielded speakers is that the 
video gets messed up, not so much that you get hum - then check out 
your cable run. It's unlikely that the video cable is going to induce 
hum into the audio cables, whether or not they're balanced. It's much 
more likely that  your audio cables are going near a power supply. If 
you have to intersect any power cables, do so at right angles.

Or maybe you have a ground loop, which means there are multiple paths 
to ground. First , plug everything into the same power strip. If that 
doesn't do it, well, you're not supposed to lift the grounds (i.e. 
use a 3-conductor > 2-conductor adapter) to get rid of hum, but 
everyone does it. Just be aware that if there's ever a short in the 
line and you happen to be holding the monitor or speakers between 
your legs, the electricity is going through your nuts instead of the 
ground wires you've lifted.

  CRT monitors operate at high voltages and have power caps that hold 
those voltages for a long time, so I'd lift the powered monitors' 
grounds and not the monitor's grounds.
-- 

Nick Batzdorf
818/905-9101, cell 590-9101, fax 905-5434