laptop noise

[chequersroadshow]

Hi,
Anyone got any idea how i can cut out the interference through my speakers when my laptop is plugged into into the mains while using ???
Regards
Rik

[Shaun]

A Ground Loop Isolation will solve your problem. Pretty cheap, around a fiver.

Welcome to the forum. If you could, have a little read HERE. Thanks.

[Nakatomi]

Better to just break the ground at the mixer input than use one of those nasty ground loop isolators. I did this by modifying an RCA cable & disconnecting the shields (the outer part of the RCA plug) at one end.

[Excalibur]

Better to just break the ground at the mixer input than use one of those nasty ground loop isolators. I did this by modifying an RCA cable & disconnecting the shields (the outer part of the RCA plug) at one end.

We haven't been told whether there's an external sound card being used, or the laptop's internal one. Often, using a decent external one can cut out the interference. Also, if there's a ground lift switch on the amplifier ( or active speakers ) that too can be a simple and effective way to stop the noise. I was using a tablet straight into an active speaker, and had a lot of mains hum, until I used the ground lift switch.

[DazzyD]

Better to just break the ground at the mixer input than use one of those nasty ground loop isolators. I did this by modifying an RCA cable & disconnecting the shields (the outer part of the RCA plug) at one end.

Why are they "nasty"? They are a simple solution to the problem of static noise generated from a power transformer and transmitted in to the audio loop. I used to use them on all my systems where there was an issue. That's before I switched to using external soundcards which do the job themselves.

The other solution is to incorporate a (more expensive!) DI box.

Anyone who is not top-notch with their wiring skills, I'd have to advise to refrain from modifying cables and leads. A simple little error could cause a short which in turn could cause damage to any equipment it's connected to. Leads are manufactured to a set standard for a certain purpose and, of course, modifying them means any damage caused is your own fault. Safety first!

[Nakatomi]

The cheap isolators are nasty because they use dirt cheap transformers which is why DI boxes are far more.expensive - they use proper audio transformers.

Another solution is to replace the laptop psu with a 'floating' one, i.e. one with a 2 pin Mains input connector.

[yourdj]

Another solution is to replace the laptop psu with a 'floating' one, i.e. one with a 2 pin Mains input connector.

That makes sense. Being low voltage it would not pose too much of a risk either, unless it was dunked in a bucket of water. My iPad always buzzes when its on charge and plugged into my little mixer. Thats no problems as I have a battery pack to charge it if I am using it for backup. On airplane mode it last for hours anyway.

[Nakatomi]

I suspect the only real reason something low voltage like a laptop power supply needs a Mains earth connection is to help reduce the amount of noise it puts on the Mains. The laptop DC ground likely won't be connected to Mains earth directly anyway it'll be through a capacitor meaning it has no protective value at all. If anything it allows small currents to leak across, hence the audio noise.

A replacement floating power supply from a reputable manufacturer will be double insulated & very safe. Plus it's more convenient and won't degrade your audio like a dirt cheap isolator will.