Ask MetaFilter questions tagged with hum

AC adapter making my speakers buzz -- and it's not a ground loop.

ori — Mon, 23 Mar 2009 19:13:24 -0800

New, generic AC adapter is causing my computer speaker system to hum. I thought it was a ground loop, but a cheater plug (fitted on the jack of the AC adapter) didn't help. (The speaker system itself is not grounded.) I know it's the AC adapter, because if I run my laptop on battery power, the hum disappears. Anything I can do, short of forking out $70 for an original adapter? This adapter has been working fine otherwise.

I'm using an external Sound Blaster Live! 24bit as my sound card, but the problem persists when I switch to the on-board sound card.
The speaker system works perfectly well with other laptops.

In short -- it's the AC adapter. But what should I do?

Could someone help me to fix an old TV ?

nicolin — Sat, 11 Oct 2008 10:52:09 -0800

I've just inherited an old Hitachi crt TV (15 years old). Since I've turned it on, it has never ceased to make an annoying humming. I thought it came through the speakers, and then realized that the noise was the same even if the sound was turned off. The noise is distinctively louder when the image is bright, and softer when the image is dark. I gather there's a problem with the tube energy supply, but after this point, there could be lions, dragons or monsters behind the tube, it's terra incognita. So could someone provide me with an explanation and some easy instructions to solve the problem ? Thanks !

Help me kill the hum

Artifice_Eternity — Tue, 15 Jan 2008 19:31:39 -0800

MusicGearFilter: I've got a hum in my recording/performance setup. I think I know how it's getting in -- a balanced mic cable going into a piece of gear with an unbalanced jack. How do I fix it? Full details within. My headset mic has a permanently attached cable with a XLR plug on the other end. I connect this to an extension cable, which has an XLR jack on one end and a TRS plug on the other. So far, it's a balanced signal.

The next step is where I think the problem occurs: I'm plugging that TRS plug into my Zoom G2 guitar effects unit, which has a 1/4" (mono) input jack. Then I send the signal out to my mixer.

I only get the hum when I have the G2 in the loop. When I plug either the mic's XLR plug or the TRS plug from the mic extension cable directly into my mixer, the hum disappears.

The hum also disappears if I touch any conductive part of the signal chain -- the mic cable connectors, the G2, the G2-to-mixer cable connectors, or the mixer itself. Apparently I am grounding everything with my body.

As far as killing the hum at its source, I've tried that. A lamp dimmer was the worst offender, but I'm still having some problems with the power adaptors for my music gear and some of my computer peripherals.

Any suggestions on how could I fix this? Is there something I could insert somewhere along the chain to ground everything? This is my first experience dealing with this kind of issue, and my Googling hasn't produced any useful answers so far. The ideal solution will be workable both at home and when I play out.

Stupid Low Hum

superbird — Thu, 01 Nov 2007 17:46:11 -0800

Why is there a low hum when I record with Vista? I'm using audacity and plugging a headset straight into the mic jack. My friend and I have a podcast and every time we have to do the Noise Removal thing which really makes it sound kind of bad.

Does anyone have any ideas as to what might be causing this or how I can get rid of the sound?

(I have a Gateway MT3705 with Vista and a SigmaTel Sound Card.)

Name that MIDI

mzurer — Fri, 04 May 2007 14:46:07 -0800

What is this song stuck in my friend's head?

Getting rid of the phone buzz?

kamelhoecker — Thu, 12 Apr 2007 08:18:42 -0800

My phone has a loud buzzing noise. When I touch the screw on a lightswitch plate, sink faucet or a metal lamp, the buzzing stops. What is happening – and more importantly how can I use the phone without having to ground myself? My phone service is through my cable provider. The cable comes into the house, splits into a box for internet (cable "modem") and into another box for my phone service. My phone connects into my "phone box" with a standard telephone wire.

I did some research and my hum/noise problem sounds like a ground loop – except that my phone, internet modem, router, laptop, etc. are all not grounded. (They have only 2 prongs. But maybe the cable is grounded.)

Also, confusing (to me) is the fact that the problem goes away when I am grounded. What does me being grounded have to do with my phone?

Help with my Telecaster and HUM!

jimmyhutch — Mon, 12 Feb 2007 18:28:31 -0800

Telecaster Hum... Why won't it GO AWAY? Please help, I just installed some new pickups. I received a new set of Telecaster Pickups for Christmas this year, and this weekend I 'operated' on my Tele to install the new pickups.

The reason I wanted them was that before I had these pickups and just had the stock pickups that came with, I got horrible noise out of my amp when not touching anything on the guitar. I touch the strings, the hum mostly goes away.

The pickups I got were the Vintage Strat Noiseless Pickups.

Now, I have another problem that I cannot figure out...
I get a hum NOW from the metal parts of the guitar and not the strings. WHen I removed the bridge pickup last night I noticed that there was a loop that hooked into the screw that held the pickup in place, and the new noiseless bridge pickup did NOT have this loop. I installed it as is, and this new problem with hum has developed. Do I need to go in and strip the lead down and insert that loop back together around the mounting screw? This isn't making sense to me. All of my solder connections are clean and unbroken, and the install itself is flawless.

Also, with the little silver lipstick pickup (the one farthest away from the bridge), there is a considerable amount of play in the "up/down" motion of the pickup. We're talking about the little silver one - it feels like I need to add yet another one of the little rubber bushings on each screw as to hold it down - it kind of tilts to the front, and it rattles a LOT. Do you think that another bushing, making a total of two bushings on each one of the two screws that holds the little pickup in place would help? I can't imagine it would hurt...

Telecaster fans, guitar techs, and electrical engineers, please lend me your advice. I love my telecaster very much - I just want this hum gone!

Humless DC->AC Power Inverter?

odinsdream — Tue, 15 Nov 2005 18:44:16 -0800

What DC to AC power inverter can I buy for use in a car that won't contribute hum to an audio signal from devices it powers? I've currently got a cheap one-outlet low wattage DC -> AC converter that I use to power my laptop in the car. I use a tape adapter to play music from the laptop through my car stereo.* When I have the laptop plugged in to the power, there's a considerable hum in the audio coming through the speakers. I can almost completely eliminate it by unplugging the power. Of course, this means the laptop eventually dies.

What DC->AC power box will let me keep the laptop plugged in without the hum in the audio? I'm hoping to pick it up tomorrow, perhaps at Best Buy or similar Box Store.

*using predefined playlists with the lid closed and all that jazz - let's not discuss driving distractions and all that.

Wow - that really hums

russmail — Wed, 13 Jul 2005 09:32:23 -0800

HumFilter: how do I stop the audio connection from my DVD player humming? I have a power amp with L & R RCA inputs. Connected to the inputs is the master output of a two channel mixer (effectively acting as a pre-amp). Connected to the inputs of the mixer are two CD turntables and a DVD player.

Once I connect the video output from the DVD player to the TV, I get a big audio hum. However, if I take the mixer out of the equation and connect the audio from the DVD player directly to the power amp, I get no hum.

So I'm assuming the hum is from the TV, but why am I getting it when I run the audio through the mixer and not direct to the amp, and how can I fix it (all connections are RCA btw) - is it something to do with grounding?