Another Subwoofer Hum Question
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| Posted on February 12, 2012 at 08:06:55 | ||
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Posts: 1800
Location: Omaha NE Joined: September 8, 2006 |
I sold an Infinity SSW-210 powered subwoofer. It is a mono unit with two line level inputs, a plate amp, and two 10" woofers. I have a 30-day warranty policy, and it came back with low-level hum that was not obvious in my somewhat noisy environment. My customer has a quiet environment and the sub sits on a wooden floor; the hum couples into the floor and is annoying to the customer. When turned on with the volume all the way down there is a slight hum that I can only hear with my ear near the woofers. The volume of the hum increases slightly with increasing volume. The obvious thing to suspect is cables, so I borrowed a pair of RCA shorting plugs from the phono inputs of a receiver and stuck them in the sub's inputs. No change whatsoever, so it isn't the cables; the problem, if there is one, must be internal. Note that this is 60 cycle hum, not 120 cycle hum. The sub operates properly otherwise, and is a pretty darn good sub. We examined the amp; there are no obvious problems. The caps all look good, etc. So the question is whether low level hum is unavoidable or addressable. My technician thinks it's radiation from the toroidal transformer or from the ac leads from the transformer to the power supply. Anyone out there with experience on low-level hum on decent-quality powered subs?
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