Low audible hum from speakers???

[jayswizz]

Is there any way I can eliminate this low audible hum coming from my speakers??? I cannot hear it from my listening position, but if I put my ear within a foot of the speakers I can hear a humming noise. I know this is caused by the amp (B&K Ref 7250) but is there any way of eliminating it?

 

[W_Harding]

Hum

It could be the amplifier or it could be the source feeding the amplifier. Try this test.

1. Turn off the amplifier
2. Disconnect the source feeding the amplifier
3. Turn on the amplifier
4. Listen for hum

If the hum goes away then the source is the problem. If the hum remains then the amplifier is the source of the hum and the only way to eliminate it would be to replace the amplifier with one that does not hum.

 

[mtrycrafts]

Is there any way I can eliminate this low audible hum coming from my speakers??? I cannot hear it from my listening position, but if I put my ear within a foot of the speakers I can hear a humming noise. I know this is caused by the amp (B&K Ref 7250) but is there any way of eliminating it?

Since you can only hear it 1 ft away, that is normal amp noise. Don't worry about it.

 

[Rip Van Woofer]

It could be a ground loop. There's an article about hum and ground loops here...the "sticky" at the top of this forum!

 

[jayswizz]

I noticed that the hum is very low until I turn my monitor on, then the hum seems to get a bit louder. What can I do to minimize this? Thanks everyone for your input.

 

[MacManNM]

1. move the equipment away from the monitor
2. Buy cables with better shielding.

Chances are its the HV section of the monitor messing things up, by increasing the distance, that should go away.

 

[Rip Van Woofer]

You'll have to experiment...noise works in mysterious ways.

1) Plug the monitor's AC line into a different circuit, or at least another outlet than the rest of your gear. If it's already on another circuit or outlet, try plugging it into the SAME circuit/outlet.

2) Try moving the speakers, monitor, or other components near the monitor farther away from it (maybe it's radiated interference?)

3) Are you using any of the cheapo interconnects that came with your gear? Try upgrading to shielded interconnects. No need to spend big bucks on exotic cables - just buy something that says "shielded" on the package and looks fairly heavy and well constructed. Top of the line Radio Shack or similar should be more than adequate. Your speaker cables are unlikely culprits so don't worry about those.

4) Is your monitor or whole system on the same circuit (or even in the same room as) "noisy" devices like light dimmers or florescent lighting? If so you may need to plug everything into a different circuit. Or buy and install quieter dimmers. Or do away with the florescent lights. (Florescent lights and dimmers are more likely to induce a "buzz" sound instead of a hum, tho...)

5) As a last resort that requires real money, buy an isolation transformer and try placing it in the signal path (i.e, your audio/video inputs/outputs) between the monitor and other components until the noise is gone. For example, see: http://www.markertek.com/Product.asp?baseItem=JEN-CI2RR&cat=INTERFACE&subc
at=&prodClass=AUDHUM&mfg=Jensen+Transformers&search=0&off=

You DID read the grounding thread here, didn't you? If not, consider it required reading before proceeding and posting further!

 

[jayswizz]

Hey guys, thanks for the info. I found the problem. I have recessed lighting in my living room that works off of a dimmer. The wierd thing is that if the dimmer is turned all the way up or all the way down there is no noise. If the dimmer is at mid-level there is an increase in the hum. Does anyone know why this would happen? Easy solution for now is to just have the lights turned all the way up or completely off. Another question is will there always some minimal hum when using a seperate amplifier? The hum that my amp makes is really only audible if I get about a foot from my speakers. I cannot hear the hum if ther is sound coming from them. Again, Thanks for everybodys help.

 

[Rip Van Woofer]

See my point #4 above. Dimmers are inherently "noisy". The noise is not so much radiated into the room AFAIK but is sent along the wires to anything else plugged into the same circuit. So the simplest/cheapest solution (Choice #1) is to plug your gear into a different circuit -- if you can find one in your room.

Choice #2 is to find a specialty lighting/electrical supply store with knowlegeable help and see if low-noise dimmers are available. I'm not sure but I think they're called "solid state" dimmers. If so, buy and install them in place of your current dimmers. They're not too expensive.

Choice #3 is to spend about $200 on an AC isolation transformer (different than the "line level" unit I mentioned earlier) such as the Tripp Lite IsoLator model #IS-1000. Parts Express carries them. Plug it into the wall where your gear is plugged in now and plug all your gear into the transformer. No need for a separate circuit. Just money.

Choice #4 if you don't have a separate circuit in the room is to hire an electrician tp put one in...now we're talkin' serious money.

Choice #5 is what you're doing now.

As for your question about separate amps always being noisy: It depends! The more components you have, the more opportunities for ground loops and other mischief. Sometimes you're lucky, sometimes not. Like I said above, noise works in mysterious ways.

 

[jayswizz]

Thank you Rip Van Woofer, your input is very helpful. I am going to try a different outlet just to see if there is a difference. Right now I have 4 components hooked up: Monitor, Pre-amp, DVD, and my amp. The amp is very quite. I do hear a slight hum but only when there is no sound and I have my ear within a foot of the speaker. I do not have a power conditioner. It seems that depending who you talk to it can go either way as to if they are really worth it. I do use an A/V surge protector though. Maybe down the line I will invest in a conditioner. WOW, this gets to be a real expensive hobby!

 

[mtrycrafts]

The amp is very quite. I do hear a slight hum but only when there is no sound and I have my ear within a foot of the speaker. !

I bet it is the normal amps noise floor you are hearing. It is quite common to hear that when a system is idling and your ear is right next to the speaker.

 

[highfihoney]

a neat trick

a little trick that's easy & cheap to try is simply to plug a digital alarm clock into one of the power outlet's on the back of your reciever/pre pro or what ever,this sometime's work's by loading up the ac line's & scrubbing off a bit of noise, alot of time's this little voodoo trick will actually work & is alot easier to try before switching outlet's.

im not sure if they make it anymore or not but there used to be a product made by Audio Prism called Quiet Lines that you would plug into a spare socket to load the lines & scrub off noise,they were made with a serie's of resistor's & cap's i think.

what's sad about the alarm clock deal is that there is a company called "machina dynamica" that sell's a timex alarm clock that they call "the clever little clock" & claim it to be a "highly modded" peice of equipment that does the exact same thing for $199.

 

[zumbo]

Well now. I can dig it.