OT: amp - long cable - speaker = hum/noise?

["Raul Bonell" <raul.bonell@gmail.com>]

hi there!

i know this is way out of topic but a friend of mine
needs this info quickly to install a PA system.

he complaints about the long cables on this equation:

amp - long cable - speaker = noise+hum ?

he asked if inserting some kind of inject box between the amp and the
speaker will solve the problem.

i know about DI boxes to match impedances at line/instrument level,
but is there exists something similar for powerful signals? Silly
question, isn't?

For me this doesn't make much sense, since I think the noise is being
produced by the low quality of the sources
 (cd+mic+amp).  Maybe the proximity to some inductive sources...
Perhaps good cables will help.

 Any ideas / experiences?

Raül.

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