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Subwoofer buzz  

post #1 of 7
4/19/05 at 10:58am
Thread Starter 
I just got a new Harmon Kardon 635 receiver and hooked it up to my speakers last night. The powered subwoofer buzzes! I can minimize the buzz if I adjust the input level (on the subwoofer) but if I do this, then the input level is too high and the sub raises the rafters! All the other speakers are fine. I have the subwoofer output of the 635 connected via a 25' High quality RCA cable and then a high quality Y adapter to the two line inputs on the subwoofer.

Does anyone have any experience with these types of problems or have any suggestions?
Thanks.

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post #2 of 7
4/19/05 at 11:07am
Your post seems to indicate that you get the buzz when you turn your sub volume down, as you indicate that to correct it the input level is too high. Is this the case? That's a little odd then, usually you'll get buzz as you turn the level up, not down.

At any rate, does your sub cable wind its way near power cables? Cross power cables at right-angles only, try not to run parallel to a power cable. Even with good shielding, you can pick up a 60 Hz hum which your sub will reproduce quite nicely!

To avoid noise, it's best to set the sub output at the receiver as low as it can go, then adjust the volume level at the sub as high as you can go without getting a hum or noise. If you can't get a decent volume level at the sub before you get noise, bump the receiver sub output up by a dB and try again.

Less gain in the receiver, more gain in the sub amp.
post #3 of 7
4/19/05 at 11:14am
Let us do the easy troubleshooting first.

1. Unplug the RCA cable connected to the sub. Turn on the sub and see if it buzz. If it buzz, relocate the sub to a different wall outlet.

2. If OK on step 1, reroute the RCA cable from the receiver going to the sub. Make sure it is away from any electrical cords. Do not use the Y adaptor at this time. Just plug in the RCA to either left or right connector on the sub and see if it buzz.

3. If still OK, connect the Y adaptor and check it again.

Post back and let us know if it helps.
post #4 of 7
4/19/05 at 11:14am
Could be a groundloop problem. You can check by getting a 3 prong to 2 prong plug adapter. Of course, the buzz wouldnt increase when you lowered the volume
post #5 of 7
4/19/05 at 1:00pm
Thread Starter 
Thanks for the tips so far, I will try the trouble shooting tips when I get home tonight but to clarify: The buzz is present if the subwoofer input is adjusted to the lowest setting, as I increase the input level the buzz stays about the same until I reach about 3/4 full then the buzz starts to drop off to almost negligible, then it comes back again as I increase to full. So there is a null point as I turn the input level up, but this level is too high and too loud.
post #6 of 7
4/19/05 at 7:59pm
Thread Starter 
It looks like I have a ground loop problem. I put a two prong adapter on the subwoofer 3 prong plug and the problem went away. I don't think I want to leave it this way though for safety issues. The subwoofer and audio equipment are on the same dedicated AC circuit and nothing else is on this circuit. I did this hoping to eliminate any ground loop problems. Arghh!
post #7 of 7
4/21/05 at 6:38am
Lion,

Many post about this problem and it can be tricky. I have my sub also on the same circuit and sometimes get buzz even then. Make sure you find out what else is running in your home when you hear the buzz. I have found some combinations of things give me buzz if they all run at the same time.... Furnace, hair dyer for example. But once you shut off one, my buzz disappears. Also found that how I wound up the extra length of the power cord on the sub had some impact. Take your time and work through it slowly by eliminating all the possible combination of things. I would even go as far as turning breakers off in the panel to see if the buzz is associated with any one circuit. Of course the buzz will stop if you turn the sub breaker off.:D
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