Sub won't stop humming! Help!

kdixon1029

Member
2010-12-01 7:04 pm
Ok, I'm new to the forum and I'm sure this may have been covered at some point but I can't seem to find it. I have an Onkyo TX SR500 and an Infinity HTS20 speaker system. The sub has a constant hum, I initialy thought maybe some ground loop interference but when I push in on the input cables it goes away. It's almost like its not making a good connection. Ok now, I also have an infinity BU-1 sub. I hooked it up and it worked fine for 10 minutes or so until it too started to hum. Upon
(insert technical term) "jiggling" the cables the hum goes away. Only to return again in a few minutes. I've tried a few different cables. I have a y spliter at the reciever and heavy guage audio cables connected to the L and R inputs of the sub. Could there be something wrong with the sub Pre out on the Onkyo? Any advice is much appreciated
 

wakibaki

Banned
2008-01-08 11:51 pm
Yeah. Look at the other end where the cables connect.

It's not the sub. You swapped that.

It's not the cables. You swapped them.

It goes away when you disturb the cables. Look at the other end of the cables from the sub.

Of course, it could be miles away, or you could have the cables nailed down so the other end can't move, but on the basis of what you've said, that's where I'd look first.

w
 

infinia

Member
2005-05-15 9:51 am
SoCal
It's most probably the connector pins have cracked solder at the printed circuit board. This is really common problem in my experience. (thermal fatigue fractures) Re flow the connector joints with fresh solder with all the screws cinched tight.
 
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My solder experience is pretty limited, guitar pedals, guitar cables and thats about it. When you say re flow the connector joints, what exactly do you mean, remove old solder and apply new? How difficult is this, do I need a schematic? And finally are you sure it's not some type of grounding issue? It seems theres a lot of discussions on the web about subs humming because of grounding. I don't know, maybe I'm just looking for the easy solution : )
 
Most powered subs do not require L + R inputs if you have a LFE or Sub Out from your HT system. Try getting rid of the Y adapter at the sub end - just plug the single sub out cable from your HT system directly into the R input of the powered sub amp (the R input of powered sub amp is usually all that you need). The Y adapter could have gone bad on you.

Just a thought.......................
 
Still have that horrible hum. Both sub imputs can't be bad. It has to be the reciever output or some grounding issue. My coax cable from the street is going into my monster power HT700 and out to the motorola DCH6416 digital cable box. So I was hoping that the coax is now isolated and is not the problem. Where do I go from here. I certainly don't mind opening up the unit, but I would like to kill all the grounding theories first.
 

wakibaki

Banned
2008-01-08 11:51 pm
I would like to kill all the grounding theories first.

It's not a grounding issue per se, it comes and goes. It could conceivably be that as the equipment heats up, a poor connection get better and introduces a ground loop, but this is unlikely. In order to get anywhere though, you have to fix the intermittent connection, WHICH IS DEFINITELY THERE.

w
 
Image of sub input

I know this isn't the clearesr of pictures. The first output is the sub pre out. The solder looks pretty good at least to my novice eyes. It looks as good as all of the other joints. What exactly am I looking for? As I stated earlier the HTS20 sub will hum as soon as I connect an rca cable, without hooking to the receiver. When I push in on the cables the humming stops. The smaller sub that I have, when hooked up works fine for a little while then the same loud hum reappears. When I shift the cables around the humming with stop for a little while.


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I too found the same problem with a friend of mine an some others too. Based on my past experience on this I would suggest you.
1) Add a resistor of 10k between the ground and output. ( you can cut a cable and try this).
2) If its a two pin power-supply try inverting the pin in socket.
3) measure the voltage between the two grounds.
4) design your own simple unity gain buffer using NE3332,and add it between Sub and receiver.
 
I know this isn't the clearesr of pictures. The first output is the sub pre out. The solder looks pretty good at least to my novice eyes. It looks as good as all of the other joints. What exactly am I looking for? As I stated earlier the HTS20 sub will hum as soon as I connect an rca cable, without hooking to the receiver. When I push in on the cables the humming stops. The smaller sub that I have, when hooked up works fine for a little while then the same loud hum reappears. When I shift the cables around the humming with stop for a little while.


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dunno if u tried yet ,but have you disconneted earth from the mains 1 or both sides?