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Looper's Delight
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Better would be: long BALANCED cable - AMP - short cable - speaker which would be not noisy. noise is caused by EM radiation, which increases in impact on signal basically as a square of strength per antenna length multiple of EM wavelength. The good news is your speaker cable is carrying lots of watts, which the EM radiation will have trouble competing with. Bad news, when your signal is quiet, the radiation will sound loud. Badly engineered amplifiers that use overly simple negative feedback elimination topologies can also bring that EM noise in from the speaker line, and reroduce it, now driven by some fraction of amplifier power. Super bad news. Noise can impact the amplifier from other vectors as well, bad grounding with bad neg. feedback = massive 60hz AC hum. I've seen shielding methods (wrap the speaker wire in metal/wiremesh/ other faraday like materials) as well as really nasty volage conversion inline (think the overhead musak in the 70's department store) both of which don't seem to work well. Short answer, move the amp. :) -Miles On 5/1/07, Raul Bonell <raul.bonell@gmail.com> wrote: > 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. > > -- > The Playing Orchestra: http://www.telefonica.net/web2/tpo > Chain Tape Collective: http://www.ct-collective.com > TPO at myspace: http://www.myspace.com/theplayingorchestra > > -- ---Miles Ward