Humming in my M&K sub -what can I do?

[Jedi Master]

Even when ALL other equipment is completely unplugged, and the sub is ONLY plugged into the wall, still hums. I have to assume that it's either the 110 outlet from the wall or the internal amplifier in the sub. I disconnected the TV cable, tried various ground wire configs, etc. Should I do any of the following:

1) Buy a "line conditioner"? If so, which one?

2) Test (if there is a way of testing) or replace the "filter capacitor" or "smoothing capacitor"?

3) Test/replace the transformer?

ANY & ALL help is greatly appreciated!

 

[TLS Guy]

Even when ALL other equipment is completely unplugged, and the sub is ONLY plugged into the wall, still hums. I have to assume that it's either the 110 outlet from the wall or the internal amplifier in the sub. I disconnected the TV cable, tried various ground wire configs, etc. Should I do any of the following:

1) Buy a "line conditioner"? If so, which one?

2) Test (if there is a way of testing) or replace the "filter capacitor" or "smoothing capacitor"?

3) Test/replace the transformer?

ANY & ALL help is greatly appreciated!

If it hums with the sub just plugged in to the wall and nothing connected to the sub, then your sub amp is malfunctioning and needs to go in for service.

You can not guess what is wrong with it. You need to have a service tech find out what is wrong with it. You could do it, but you will need a circuit and test gear, such as a VOM, scope and signal generator at a minimum.

Most of these sub amps use switching power supplies, like computers, which are not easy to sort out.

 

[walter duque]

Even when ALL other equipment is completely unplugged, and the sub is ONLY plugged into the wall, still hums. I have to assume that it's either the 110 outlet from the wall or the internal amplifier in the sub. I disconnected the TV cable, tried various ground wire configs, etc. Should I do any of the following:

1) Buy a "line conditioner"? If so, which one?

2) Test (if there is a way of testing) or replace the "filter capacitor" or "smoothing capacitor"?

3) Test/replace the transformer?

ANY & ALL help is greatly appreciated!

I do have a similar problem with one of my powertowers. As soon as I start unplugging components from the wall one of my powered towers starts to hum when I plug everyting back in (since it is on one circuit) it stops. I can't figure that out either. Must be a problem in the electric line, and I do use a voltage regulator and power conditioner.

 

[jinjuku]

Even when ALL other equipment is completely unplugged, and the sub is ONLY plugged into the wall, still hums. I have to assume that it's either the 110 outlet from the wall or the internal amplifier in the sub. I disconnected the TV cable, tried various ground wire configs, etc. Should I do any of the following:

1) Buy a "line conditioner"? If so, which one?

2) Test (if there is a way of testing) or replace the "filter capacitor" or "smoothing capacitor"?

3) Test/replace the transformer?

ANY & ALL help is greatly appreciated!

Try a two prong plug (that is no ground plug) often called a cheater plug. Other than that...
I suggest the yellow pages. Look up a repair shop.

 

[TLS Guy]

I do have a similar problem with one of my powertowers. As soon as I start unplugging components from the wall one of my powered towers starts to hum when I plug everyting back in (since it is on one circuit) it stops. I can't figure that out either. Must be a problem in the electric line, and I do use a voltage regulator and power conditioner.

Your problem is different. Does you sub have a two pin plug or three? If it is two, I'm suspicious of a live neutral reversal at some point, and when you connect things up, it grounds the sub.

 

[mperfct]

I had this with my MFW-15, and lots of other people have had that as well with that particular sub. I'm using an Ebtech Hum-X, and it works pretty well. Takes the hum down 60-70%, which is less than audible, so I'm happy. Got mine off of Amazon.

I would see if you could do some electrical tests on that outlet or maybe run an extension cord to a different circuit and see if it is still there too. Before you buy a Hum-X...

Good luck

 

[zumbo]

Try a two prong plug (that is no ground plug) often called a cheater plug. Other than that...
I suggest the yellow pages. Look up a repair shop.

I do this, and it is not recommended.

I use a line-conditioner/surge suppressor/ups. My sub is plugged into this(with the cheater), along with everything else. I ran a ground from the receiver to the ups. This makes the sub connected to the receiver by the rca to be grounded by the rca connection.

In other words, if you use the cheater plug, make sure you have an alternate ground such as I have done.

I also use a cable isolator.

 

[highfigh]

Even when ALL other equipment is completely unplugged, and the sub is ONLY plugged into the wall, still hums. I have to assume that it's either the 110 outlet from the wall or the internal amplifier in the sub. I disconnected the TV cable, tried various ground wire configs, etc. Should I do any of the following:

1) Buy a "line conditioner"? If so, which one?

2) Test (if there is a way of testing) or replace the "filter capacitor" or "smoothing capacitor"?

3) Test/replace the transformer?

ANY & ALL help is greatly appreciated!

Buy one of these. Home Depot, big box stores and just about any hardware store will/should carry it and since they're basically the same, buy the cheap one. It may be that the hot and neutral are reversed and need to be corrected. It could also be in the power supply and it may/may not be a switching supply. If it's not, chances are good that a filter cap is bad or a ground lifted. I doubt a line conditioner will help this because it's not made for this kind of issue. Filter cap is a smoothing cap. If a transformer goes bad, it's usually open or partially/totally shorted. An open winding means it won't turn on at all (depending on which secondary is open) and it has a short, it will usually blow any fuse that's put in it, especially if the short is in the primary.

 

[highfigh]

The Hum-X and ground lift adaptor might work if the sub is connected to the rest of the system but this one isn't. If it was, a good floating ground adaptor (1:1 audio transformer) will usually fix it without lifting the power supply ground.

 

[TLS Guy]

I had this with my MFW-15, and lots of other people have had that as well with that particular sub. I'm using an Ebtech Hum-X, and it works pretty well. Takes the hum down 60-70%, which is less than audible, so I'm happy. Got mine off of Amazon.

I would see if you could do some electrical tests on that outlet or maybe run an extension cord to a different circuit and see if it is still there too. Before you buy a Hum-X...

Good luck

Since there is only one device plugged in there is no ground loop. The Hum-X must lift the ground somehow, as it is deigned to ameliorate ground loops.

It suggests to me those subs must develop a leak to ground, possibly because of a bad cap, or more likely a bad diode in the power supply. I would wonder in that event, if the power supply is symmetrical when that fault develops, and therefore the probability the distortion is greatly increased due to an asymmetrical wave form at the output.

It seems to me those subs are units to avoid. I would advise looking for a better unit.

 

[mperfct]

The Hum-X and ground lift adaptor might work if the sub is connected to the rest of the system but this one isn't. If it was, a good floating ground adaptor (1:1 audio transformer) will usually fix it without lifting the power supply ground.

Hmmm...my sub is on it's own circuit (it does have another outlet that powers two 3w LED step lights as well). I'm no EE, but all I know is that the Hum-X helped.

 

[Jedi Master]

Try a two prong plug (that is no ground plug) often called a cheater plug. Other than that...
I suggest the yellow pages. Look up a repair shop.

My current outlet strip is a 3-prong configuration; the sub is a 2-prong. The wall outlet is old-school 2-prong (throughout the entire house) so I had to use a "cheater" adapter to plug the outlet strip in. BUT, with EVERYTHING UNPLUGGED and only the 2-prong sub plug plugged into the 2-prong outlet, it hums like an arc welder.
**NOTE: I did notice at least a 50% reduction in humming when I simply place my hands on & around the sub...

 

[mike_wassell]

I had the same problem with my M&K sub and it was a ground in the interconnect running from the receiver to the sub. Leave the sub plugged in and disconnect the interconnect. If the buzz goes away the problem is probably in the interconnect. Try a new interconnect.

Mike

 

[zumbo]

My current outlet strip is a 3-prong configuration; the sub is a 2-prong. The wall outlet is old-school 2-prong (throughout the entire house) so I had to use a "cheater" adapter to plug the outlet strip in. BUT, with EVERYTHING UNPLUGGED and only the 2-prong sub plug plugged into the 2-prong outlet, it hums like an arc welder.
**NOTE: I did notice at least a 50% reduction in humming when I simply place my hands on & around the sub...

I would have an electrician install a dedicated 20amp circuit.

Luckily my home had a 20amp breaker in the living room for a certain section, I just replaced the outlet behind my system to accommodate the 20amp plug on my ups.

EDIT: I would also recommend that the electrician be sure the meter has an earth ground. My mothers old home didn't have an earth ground, and lightning toasted my system back then, along with many appliances in the house. Insurance paid for the equipment, and paid for the earth ground.

 

[TLS Guy]

My current outlet strip is a 3-prong configuration; the sub is a 2-prong. The wall outlet is old-school 2-prong (throughout the entire house) so I had to use a "cheater" adapter to plug the outlet strip in. BUT, with EVERYTHING UNPLUGGED and only the 2-prong sub plug plugged into the 2-prong outlet, it hums like an arc welder.
**NOTE: I did notice at least a 50% reduction in humming when I simply place my hands on & around the sub...

The power supply of that sub sub is leaking to neutral. That is potentially dangerous. You are creating a patial grounding through your body when you touch it. My best advice to you and anyone elso who owns those units, is take
them to the recycling center and run.

 

[Jack Hammer]

I've had a few friends whose subs started to hum with the power cord plugged in and nothing else connected. They tried different outlet on different circuits with no improvement. Each time it ended up being a bad amp. I'd either contact a repair shop or replace it if it's a smaller and older model that might not be worth the cost of repair.

Jack

 

[highfigh]

My current outlet strip is a 3-prong configuration; the sub is a 2-prong. The wall outlet is old-school 2-prong (throughout the entire house) so I had to use a "cheater" adapter to plug the outlet strip in. BUT, with EVERYTHING UNPLUGGED and only the 2-prong sub plug plugged into the 2-prong outlet, it hums like an arc welder.
**NOTE: I did notice at least a 50% reduction in humming when I simply place my hands on & around the sub...

Unplug the audio cable from the sub and see of the hum goes away. If it does, you have a ground loop and need to use an isolation device for the audio.

Did you connect the ground tab from the cheater to the screw on the electrical box? That needs to be connected for anything to be grounded.

You really should go through the house and check all of the circuits for correct polarity, grounds, etc, and then install grounded receptacles.

 

[highfigh]

Hmmm...my sub is on it's own circuit (it does have another outlet that powers two 3w LED step lights as well). I'm no EE, but all I know is that the Hum-X helped.

Unplug the LED light power supply and see if that matters.

Your Hum-X is an isolation transformer. You needed RCA-1/4" adapters, right?

 

[mperfct]

I should try that, even though I'm happy with things now.

Also, the HumX is a outlet-based solution. Here's a pic...

 

[zumbo]

Inside the unit.
______________
I i------------i I
.------X------.

LOL