LSi25 constant amp humming when plugged in
MarkLav
Posts: 4
Hello and thanks for reading.
My LSi25's have had a fair share of abuse, but nothing out of the ordinary and always w a clean pre-amp.
While I'm listening to music, even at low volume, no problem. They sound wonderful.
But if no music is being played, there is a noticeable humming coming from the amp in each speaker. No matter if the speaker amp power is set to On, Auto, or Off. As soon as I unplug the speaker power cord, obviously the noise disappears.
Any help would be appreciated, thanks again ...
My LSi25's have had a fair share of abuse, but nothing out of the ordinary and always w a clean pre-amp.
While I'm listening to music, even at low volume, no problem. They sound wonderful.
But if no music is being played, there is a noticeable humming coming from the amp in each speaker. No matter if the speaker amp power is set to On, Auto, or Off. As soon as I unplug the speaker power cord, obviously the noise disappears.
Any help would be appreciated, thanks again ...
Comments
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Hello,
Welcome to Polk's forum. A bit of clarification, is the humming coming from the woofer or the bass amplifier itself? -
It's coming from the bass amplifier in both speakers.
Thanks -
Usually this can be traced to the AC transformer's laminations vibrating together caused by the magnetic field. Sometimes this can be caused by slight amount of DC (direct current) being present in your incoming line voltage. There are many people who have solved this problem by using what are called "line conditioners" which work to filter off unwanted noise. You would need to use one that has sufficient current capability to accommodate your amplifiers.
Another, less expensive, approach is to simply ignore the noise as long as it isn't heard at the listening position. -
One other possibility is one of the electrolytic filter caps on the AC side is going bad.
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Did anything change electrically in the room where the speakers are before the hums became noticeable? Maybe move one speaker to a different room and plug it in there to see if the amp inside still hums?
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Yes, thanks. That's been my solution so far, just to unplug them when not in use.
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Do you think it would help to remove the amp from the speaker cabinet, and give it a blast of canned air?
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I don't believe that would be of help. It's a sealed system, not much dust gets inside to cause problems. You could make sure all of the screws on the outside of the cabinet are tight. In the past I have reduced transformer lamination noise by isolating the transformer from the metal chassis. Adding grommets to the mounting holes of the transformer and using sound deadening materials, such as Sorbothane pads, to decouple the transformer from the mounting plate. A friend has used epoxy to encase a noisy transformer, this method used to be very common in audio products, called "potting". All of the vintage H-K, ARC amps used potted transformers and were quiet.
