Onkyo Subwoofer problem

[bostock]

I'm experiencing a constant hum from my subwoofer whenever it is connected to my Onkyo 605. It doesn't matter if the receiver is on standby or it is fully on, the noise is constant. I have changed out the sub and the cable, so I'm sure the problem is the receiver.

Any ideas what the problem might be?

[luvtolisten]

Hi, sounds like you may have a ground loop, or a bad connection.
Make sure all your connections are good, not just the sub, the input or source connections as well.
Try plugging the subwoofer, into another circuit altogether. Not just another outlet, but another circuit(run an extention cord if you need to) to see if it goes away.
Be sure your sub cable isn't running parrellel to any AC or power cords.
There is also some good advice on ground loops in the Amp/Preamp Forum here, (Music Fidelity Hum) where you'll find more ways of eliminating ground loops. Good luck!

[Kevio]

Ground loop is the obvious candidate. A ground loop is when a device has two separate connections to ground. With two connections, there's the possibility for extraneous AC current to flow in one connection and out the other. The current induces a voltage which the audio equipment reproduces as a hum.

So, what are the connections to the subwoofer? You have an unbalanced line-level audio connection. This connection features a ground. You have an AC power connection. Typically this is a 2-prong connection so no ground connection is present. Does your subwoofer have a 3-prong plug? Are there any other connections to the sub?

[bostock]

I use the standard subwoofer to connect to the receiver. I've also tried swapping out the cable, a different sub, and tried plugging everything into a different room.

The subwoofer uses a 2 prong plug and there is nothing else plugged into the receiver. When all the other speakers are plugged in I don't get any hum from them, only the sub. Also, switching from cable/dvd/cd etc. and changing the volume makes no difference in volume of the hum.

The hum is also evident when the receiver is on standby.

Quite confusing.

[Luvin Da Blues]

The subwoofer uses a 2 prong plug and there is nothing else plugged into the receiver.

Is your sub plugged into the receiver? If it is, try another wall outlet for the sub.

[RoadRunner6]

Never run a sub's power cord thru the receiver. Check both ends of the sub's RCA cable from the receiver to the sub. Make sure there is a very positive connection. Then try a different RCA cable, any RCA cable is fine. Try reversing the plug power plug from the receiver to the electrical receptor.

[luvtolisten]

I would also try using the high pass (speaker terminals) on your sub. Perhaps there is a problem with the sub output (weak internal connection, bad solder joint)) of your receiver, since using a different circuit or sub made no difference.

[Kevio]

Never run a sub's power cord thru the receiver.

Why not?

[RoadRunner6]

I can not give you an electical engineer's answer, but have read this many times to help prevent this very problem. Several sub manufacturers recommend plugging the power cord from the sub directly into the wall (or with its own surge plug) instead of thru the receiver or a common surge protector. I can only presume they have a legitimate reason.

RR6

[bostock]

The cables are definitely ok as I have the same problem with several different cables. The receiver plugs directly into the wall, as does the receiver, and no other electronics are on that particular circuit.

[RoadRunner6]

Why not?

Quote from my Outlaw subwoofer's owner's manual:

....."CAUTION: Due to the power requirements of the LFM, it must not
be connected to the accessory outlets on a receiver or processor. If a
power-strip or surge protector is used, make certain that it is rated to
accommodate your LFM’s power requirements....."

Apparently this is more of a power problem. Don't know if it might possibly cause hum.


Bostock:

#1 ... Do you have your receiver connected to a cable TV or Satellite feed? If you do, you might have a grounding problem in the coax cable from the cable company or satellite feed. Have a service call and get them to correct the grounding problem (if #2 below doesn't work). I had a hum problem in one of my old Energy subs that I could not get rid of. I lived in an apartment with a connection directly to the wall cable TV outlet. I moved a couple of miles away about a month later. I hooked up my system in the exact same manner except that it was a brand new condo with the same cable TV company and the same direct to the wall cable connection. Suddenly I had no more hum.

#2 ... Try using an RCA sub cable that has directional arrows on it. This indicates it is a cable that has the shielding connected only at one end (it has nothing to do with the flow of the signal, which can go in either direction). Install this cable with the arrows pointing from the receiver to the subwoofer. This might be easier to try first and could solve the problem if you don't have a cable/satellite feed grounding problem.

RR6

[bfalls]

Is it possible to join the grounds from the two components together? I know many receivers have a grounding screw. I believe it was originally intended to ground a turntable to the receiver. You get hum because there's a potential difference between the two grounds. Joining them together will make them the same potential, so there's no 60Hz level to amplify.

[bostock]

At first I thought it was a ground loop problem, but I have disconnected everything from the receiver, and turned off the cable box, so I would have thought the hum would have stopped. Also, I've tried it in several different rooms, on different circuits, and still the same hum. I should also note that the sub just isn't working, other than the hum. I don't think the sub is the problem as one I know works fine has the same problem when attached to the receiver. When I used the white noise test in the setup menu all the channels work, except for the subs.