Hum Loop With Laptop Power Supply

[sputnick007 0]

I am having a problem with a hum loop from my laptop power supply through the speakers.

I only get it when the power supply is plugged in.

I have found a cure by using an extension lead for the power supply and disconnecting the earth lead although I`m not keen on this idea, but European laptops dont always have and earth lead.

 

[DJTREV 0]

Have you tried a ground loop isolator.They are not very expensive and you connect them between your laptop and your mixer

[McCardle 1]

I have found a cure by using an extension lead for the power supply and disconnecting the earth lead although I`m not keen on this idea,

 

You shouldn't be keen on doing this either, you are not only risking your own life but those of your audience too. I've discussed this in some depths on threads like this previously, especially as the earth can also have some physical function within the PSU design, such as playing a role in overvoltage protection circuitry protecting against if the PSU fails or suffers flashover (you really don't want 240v AC going into a laptop designed for 18v DC)

 

IMO, removing the Earth to prevent hum / earth loops is akin to disconnecting your cars' braking system just because you have a seized caliper, sure it may easily cure the immediate problem, but risk killing you in the process.

 

Its also something which is covered in HSE

 

http://www.hse.gov.uk/pubns/indg247.pdf

 

Just "Because we are DJ's" doesn't make us immune to responsibilities

 

Health and Safety at Work etc Act 1974 (HSW Act)

If you are paid for entertaining, what you are doing probably

comes within the scope of the HSW Act. If you are self-

employed (even if entertaining is not your main job), you have

to look after your own safety and the safety of anyone else

who might be affected by what you are doing (section 3 of the

Act).

 

but European laptops dont always have and earth lead.

 

Shucko plugs do have an earth, although generally its by way of small recessed tabs on the top and bottom of the plug, and so not as obvious to see as the main large phase and neutral pins. The only PSU's that don't, are the ones which use the twin core 'figure 8' connector, and these will be designed not to have an earth in their circuitry and will also be double insulated.

 

Copper prices are at an all time high, believe me the manufacturer will not be going to the expense of suppling three pin connectors and three core flex, if using two core was possible .

 

DJ Trev has given you a perfectly safe and effective alternative. :Thumbup:

Edited February 28, 2013 by McCardle