Subwoofer is humming.. please help!

[Johnny Canuck]

Hey guys

I noticed last night a faint hum coming from my subwoofer, an Hsu STF 3. It may have been there for some time and I never noticed, or it might be something new. it's not really loud, but it is there. I am hoping I never damaged my sub. A few weeks ago I had a scare with my system. I heard a few loud pops and I think it was because my receiver was switched accidently to "Phono" and I had an HDMI cable coming out of my digital box and sitting on the floor as i have this inconvenience of switching HDMI cables back and forth if I am watching a movie or if I am watching TV. I don't think anything damaged as I turned off the amp really quick. The NAD amp I have going into my receiver may have been the culprit..

anyways....the sub now hums. I tried disconnecting the TV cable from the wall, hum is still there. When I plug the sub cable into the filtered jack, the hum goes away.

I tried a different plug in the wall, still hum. This was after I unplugged it from my Tripplite powerbar. I am going to experiment tonight and unplug each component one by one. I assume it's receiver/amp related as the hum goes away when plugging into filtered and using the sub's crossover.

How does one know if you have a sub amp issue? I guess it either works or it doesn't? I also noticed a small crackle when i turn the volume up or down on the sub if left for awhile. I always have the sub to "on", not auto. Is this crackle normal? It's very faint, but still there.

The sub cable is a Monster 20 footer..too long but it's worked good for me. I will try a different cable, just a simple cheap video cable with shielding, to see if it's the cable.

Suggestions??? Thanks everyone. I sure hope the Hsu is OK as I do not want to pay for shipping to have it repaired.

JC

 

[Leprkon]

this link might help.

http://www.audioholics.com/techtips/setup/avhardware/groundloopcableTV.php

 

[Johnny Canuck]

thanks leprkon but I don't think this is a ground loop issue. I just tried something. I took the sub out to the next room, disconnected all wires except the power cord. Plugged it in, turned it on, I hear hum. Just faintly. Not hooked up to anything.

Is this normal????

Can somebody with an Hsu STF 3 please try this? Take your sub out of the room it's in, plug it in to a wall, crank it to at least 3/4 and listen for a hum. Something else. When I touched the tiny screw right next to the volume knob, the hum got louder. What's up with this? Anyone?

Is this sub supposed to have a faint hum when it's turned up past 3/4? If I wiggle with the volume knob, the hum comes and goes.

 

[hohmann]

60 Hz. Hum

First of all I am a new member and I am very happy to be able to chat on line with other Audiophilers. I always felt that this is a great service that this forum provides and I would like to contribute. Bare with my English.
I would like you to do a small test. Disconnect all inputs to the sub, and then get a cheap RCA and strip it *( expose the conductors) Basically short the RCA and then plug it into the subwoofer input. Turn the gain to the normal listening level IF you hear any noise, then this is your best noise floor. IF you can live with it. It is fine.
IF the noise is reduced, then it appear that the input stage to the subwoofer is too sensitive. and it can act like a microphone and it picks up the 60 Hz ( one possiblity.) that are other possibilities such as poor DC supply to the preamp. Bad transformer winding ( possibly too lose, the winding vibrating) SO short of opening the unit and void the warranty you would not fix the problem.anyway try the shorted RCA and see what you get. Another idea provide noise is lowered with the shorted input, is to use an RCA that has three conductors, The two conductors are shorted to create shield at the source and not shorted at the sub. THis is your best shot. OF course assuming that there is no ground loop. IF you have a ground loop, then I would try this short cut. Try to ground the shassy frame of the components used CD, DVD, and other units to the processors. This often reduces the Ground loop. Also as the form has posted before check out the Cable TV box frame.,Jump a wire on the outside frame of the box to the processor so that the frame have one ground reference.
Good luck

 

[hohmann]

If the hum totally goes when you shake the gain, then the gain knob is damaged. You need sevice

 

[Wid]

It would be best to shoot an e-mail off to Hsu or just give them a call. If the sub didn't have the hum before it sounds like something went wrong in the amp.

 

[Johnny Canuck]

Thanks guys..I sent Hsu an email

It seems ok after i wiggled the volume knob...but yeah, for piece of mind I think the amp should be looked at. Does this mean packing up this 100 pound beast and shipping it??? Geesh

JC

 

[Mr. Lamb Fries]

Ask them if you could just send the plate amp. I think Buckeyfan did that with his cadance x-sub. be sure to get the ALL CLEAR from them before you open it to mail. That could void the warranty. If they dont allow you to, then you would have to send the whole thing. There may be a local store that is certified to work on them and still use the warranty. once you hear from them, be sure to explore you options.

 

[Johnny Canuck]

Thanks..

I spoke to Dr. Hsu personally (not sure what his doctorate degree is in but anyways... )

Rocelco in Canada is the Hsu distributor and they are going to send me an amp/plate..apparantly it's not hard to change the amp. I am not that "handy". I hope it's not too difficult, maybe anyone who has changed a sub amp can help me???

JC

 

[zumbo]

Thanks..

I spoke to Dr. Hsu personally (not sure what his doctorate degree is in but anyways... )

Rocelco in Canada is the Hsu distributor and they are going to send me an amp/plate..apparantly it's not hard to change the amp. I am not that "handy". I hope it's not too difficult, maybe anyone who has changed a sub amp can help me???

JC

It should be easier than connecting equipment.

 

[Wid]

You should e-mail Hsu tech support. They do have detailed instructions on the amp removal.