Mains Hum - Earth Loop

tems · Post by **tems** » Thu Apr 03, 2008 6:43 pm

I'm getting a massive amount of mains hum through my set up and have dont some research and found this is to do with what's called a earth loop where things are running on different voltages. I'm using a laptop and it's find when it's not plugged in, but hums like an annoying bastard humming a really repetitve tune to drive you mad with the mains in.

In maplins ive found you can get one of these to isolate the hum....

http://www.maplin.co.uk/Module.aspx?Mod ... 4&doy=26m9

The only problem is that this is for phono connections and i'm running monitors straight from the TRS output which are quarter inch jacks.

I knoe you can get converters from phono to 1/4", but would this effect the sound quality?

Can anyone shed any light on the best way to get round this at all? anyone with similar problems?

i would just keep the mains unplugged, but it eats the CPU and the compter can't hack it

FSTZ · Post by **FSTZ** » Thu Apr 03, 2008 6:51 pm

what you have is an improperly /poorly grounded CPU in your laptop

nasty noise... 60 cycle hum, innit?

tems · Post by **tems** » Thu Apr 03, 2008 6:54 pm

Yeah, thats the one. The kind that makes you want to tear your ears out! Any ideas on how to get round it??

kato! · Post by **kato!** » Thu Apr 03, 2008 7:16 pm

Ok you can get a device called a power conditioner, which will improve power quality and reduce noise greatly. The only downside is that this device is quite expensive, I think around £90. That ground loop isolater is only useful if the noise, is being created by a specific piece of equipment and not your mains supply

kato! · Post by **kato!** » Thu Apr 03, 2008 7:20 pm

Actually sorry not £90, you get various cheaper ones. Phonic PPC 8000E is £49.99.

tems · Post by **tems** » Thu Apr 03, 2008 9:34 pm

Safe for the reply Kato!

I'll keep that one in mind

I had a look around and found this>>>

http://www.behringer.com/HD400/index.cfm

it takes the 1/4" TRS jacks, so going to try this out first as it's a bit cheaper and then if that fails i'll look at getting the Phonic PPC

Sharmaji · Post by **Sharmaji** » Fri Apr 04, 2008 12:40 am

are you using balanced TRS cables? or just standard 1/4" TS cables?

kato! · Post by **kato!** » Fri Apr 04, 2008 3:01 am

TEMS wrote:Safe for the reply Kato!

I'll keep that one in mind

I had a look around and found this>>>

http://www.behringer.com/HD400/index.cfm

it takes the 1/4" TRS jacks, so going to try this out first as it's a bit cheaper and then if that fails i'll look at getting the Phonic PPC

Yeah seems ok for what you need, but it is behringer! They arent the most reliable manufacturer! So be careful. I was thinking that the problem you have may be a result of noise from say the hardrive in your laptop, but to be honest I would need to see/hear it for myself, I'm still sure it's a problem with the mains, as a colleague of mine had exactly the same problem and the power conditioner sorted it, maybe it will for you also, but I can't gaurantee it, sorry.

chris addict · Post by **chris addict** » Fri Apr 04, 2008 12:26 pm

I'm getting a massive amount of mains hum through my set up and have dont some research and found this is to do with what's called a earth loop where things are running on different voltages. I'm using a laptop and it's find when it's not plugged in, but hums like an annoying bastard humming a really repetitve tune to drive you mad with the mains in.

In maplins ive found you can get one of these to isolate the hum....

http://www.maplin.co.uk/Module.aspx?Mod ... 4&doy=26m9

The only problem is that this is for phono connections and i'm running monitors straight from the TRS output which are quarter inch jacks.

I knoe you can get converters from phono to 1/4", but would this effect the sound quality?

Can anyone shed any light on the best way to get round this at all? anyone with similar problems?

i would just keep the mains unplugged, but it eats the CPU and the compter can't hack it

word for word. I have exactly the same problem and it's fuckin annoyin. spoken to a number of people abt it and each has given me a different piece of advise. recently looked at these ground loop noise isolators such as the one in maplin. the behringer one also looks quite tidy but I'm reluctant to shell out for sumthin if it don't sort the problem so any feedback from som1 who's used one would b much appreciated.

tems · Post by **tems** » Fri Apr 04, 2008 2:33 pm

TEMS wrote:are you using balanced TRS cables? or just standard 1/4" TS cables?

I'm not sure to be honest. One side sounds alright, the other doesn't so i guess it could be one of each! The box i'm getting should convert unbalanced to balanced though so hopefully all will be cool...

Actually, scrap that, it's coming through both again now! I think it could be the hard drive noise as it makes wierd noises when i open pages etc.[/quote]

tems · Post by **tems** » Fri Apr 04, 2008 2:35 pm

Kato! wrote:
TEMS wrote:Safe for the reply Kato!

I'll keep that one in mind

I had a look around and found this>>>

http://www.behringer.com/HD400/index.cfm

it takes the 1/4" TRS jacks, so going to try this out first as it's a bit cheaper and then if that fails i'll look at getting the Phonic PPC
Yeah seems ok for what you need, but it is behringer! They arent the most reliable manufacturer! So be careful. I was thinking that the problem you have may be a result of noise from say the hardrive in your laptop, but to be honest I would need to see/hear it for myself, I'm still sure it's a problem with the mains, as a colleague of mine had exactly the same problem and the power conditioner sorted it, maybe it will for you also, but I can't gaurantee it, sorry.

Yeah, i could be the hard drive in the laptop. There seems to be a constant high pitched sound coming from somewhere in the laptop when it's not plugged into anything else. Strange that i only get the sound through one speaker when they're plugged in though.

tems · Post by **tems** » Fri Apr 04, 2008 2:45 pm

Oh my dizzle! My quotes have gone crazy! think i hit edit and not quote for the first one!!!!

7 below · Post by **7 below** » Fri Apr 04, 2008 3:09 pm

I had good results using the ground loop isolater from Maplins for my old laptop (which also hummed whilst plugged in) - so I reckon its worth a gamble.

Phono to 1/4" converters will reduce quality, but probably not by a noticeable amount.

daft cunt · Post by **daft cunt** » Fri Apr 04, 2008 3:16 pm

You need to try plugging the monitors to a power supply dedicated to them. No other device should be plugged to it.

tems · Post by **tems** » Fri Apr 04, 2008 3:17 pm

I got that ground loop isolator from Maplins as i have two outs on my soundcard. Normal phono which goes to my standard amp and speakers and then the TRS out which my monitors and sub are plugged into.

Plugged the ground loop isolator in to the phono loop with my amp and the hum has gone. I have to turn it up really loud to get any kind of hum now, louder than i'd ever want to use it.

So the good news is I've managed to get rid of the hum through one side

now i've just got to wait and see if the behringer thing works on the trs side. Lets hope so!

tems · Post by **tems** » Mon Apr 07, 2008 10:10 am

Safe Daft tnuc. I had them plugged into their own power supply and it was still happening.

The behringer HD400 arrived this morning. Plugged it in and simple as that, the hums all gone

So the ground loop isolator from Maplins worked on the phono side and the Behringer is taking care of the TRS inputs and outputs now and my system has no hum anymore

HAPPY DAYS

Cheers for peoples advice on this and hopefully this will be of some use to other people too.

badger · Post by **badger** » Mon Apr 07, 2008 11:16 am

this is only slightly related but thought i might just add it on here rather than starting a whole new thread

in drunken retardness i've managed to rip out the earth cord from one of my technics 1200s and i was wondering if anyone knows how to reattach it. i've tried google searching and come up with nothing. i remember there was an online guide for things like because i used it when the power switch broke, but i can't remember where it is or find it with a search

can anyone help?

cheers

Mains Hum - Earth Loop

Mains Hum - Earth Loop

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