OT: Help me find my hum!..please

sc · Post by sc » Fri Dec 10, 2004 2:19 pm

i was reading a website/msg board the other day that delt with this problem exactly, but i forget which site it was and it's driving my crazy.

the problem occurs ONLY when i have my laptop plugged in. when it's running on battery, i've never had an issue (aside from it not lasting very long).

i get the hum even when i have the simplest set up possible:

P4 M 2.5 GHz Laptop
M-Audio F410
Tannoy Reveal Actives

from the above info, i've come to the conclusion that the power supply is causing the problem (cause i'm smrt). however, it is a grounded plug (3 prongs).

for some reason i have an old powerbar that, if plugged in the right way (it's very very touchy....if i nudge it with my foot, i lose power) i get no hum. it's a good temp solution, but i'd really like to clear the problem up asap.

any ideas would be greatly appreciated...

glaive · Post by **glaive** » Fri Dec 10, 2004 2:40 pm

You need a ground adapter for your laptop. It's a little plastic piece that you put of the part of the AC plug that goes into the wall. There is a huge thread on this board about it, but I don't know the URL offhand.

Aural Chaos · Post by **Aural Chaos** » Fri Dec 10, 2004 2:51 pm

actually,you need to UNground it.One of those 2 prong to 3 prong adapters,found in any hardware store for about a buck.Used to plug in a grounded 3 prong plug into an old outlet that doesn't have the third hole fro the ground part of the plug.That will get rid of the ground loop,and the hum.At least it's necessary on my Inspiron.

glaive · Post by **glaive** » Fri Dec 10, 2004 2:54 pm

Yeah, that's what I meant.

I've got an Inspiron 5150 and the adapter gets rid of the hum.

sc · Post by sc » Fri Dec 10, 2004 3:13 pm

thanks guys.
though i do remember trying an extension cord that was 3 to 2 and it'd didn't seem to do the trick, but it's worth a shot

sqook · Post by **sqook** » Fri Dec 10, 2004 3:29 pm

Ungrounding electrical devices which were intended to be grounded is never a bright idea. Sure, it'll work... but for how long? You should contact the laptop manuf/vendor and see if you can get a new power adapter (if it's still under warranty, that is). Otherwise, you can buy generic or universal power adapters at most computer elecronics shops.

leisuremuffin · Post by **leisuremuffin** » Fri Dec 10, 2004 3:37 pm

Well sqook, bright or not, thats what gets rid of 60hz hum from ground problems.

I had this very same issue come up with a headphone amp in a session last week. Lots of 60hz hum, and it went away as soon as i used a ground lift. (two prong adaptor)

-m

AdamJay · Post by **AdamJay** » Fri Dec 10, 2004 4:56 pm

yea it is potentially dangerous, but i admit that i do it too, and have done it for 3 different laptops plus a couple desktop over the years and have never felt the wrath of that "potential danger"

generally when i am overseas, i have to do it anyways as the foreign plug adapters i have only take 2 prong and output to 2 prong anyway.

buzzcock · Post by **buzzcock** » Fri Dec 10, 2004 5:16 pm

If you are worried about un-grounding your computer, here's something else you can try:

Plug EVERYTHING that is in your set-up that runs on AC into the SAME grounded wall outlet (using a grounded powerstrip, if need be). Isn't as sure-fire as the ground lift idea, but it could work.

kennerb · Post by **kennerb** » Fri Dec 10, 2004 6:54 pm

I also have an Inspiron ( I'll never buy from Dell again) and have that issue. I have been through three power supplies to no avail. One thing that works is to clamp ferrite magnet rings onto the cord and that seems to break it up.

Aural Chaos · Post by **Aural Chaos** » Fri Dec 10, 2004 8:16 pm

It's not that there is anything wrong with YOUR power supply.They ALL (Dell Inspirons) do that.It's not "defective",just poorly designed.
I should have put in a disclaimer "Dont open up your laptop's housing and poke around in there while defeating the ground on the power supply"

Moonburnt · Post by **Moonburnt** » Sat Dec 11, 2004 1:26 am

Don't do it! Get a ground loop isolator instead, that sits in your audio chain, just before your speakers, rather than sacrificing the ground on your power supply. It works brilliantly, doesn't introduce any audio artefacts, and solves this problem whenever my lappy is plugged in at home. It's NOT entirely the power supply's fault either, because when I plug in at different locations I get different results half the time, so it seems more like a "device conflict" with the wiring of the rest of the building, not that I am very electrically qualified to make such assumptions, but that's what it seems like. You can get them from car audio shops for $fuckall.