Interference from laptop plugged into amplifier

[admin_exported]

When I plug my laptop into my old faithful Marantz SR4300 (3.5mm to phono) to while watching movies, listening to Spotify or whatever, there's a really irritating buzzing, almost white noise / radio interference sound comes through.

If I remove the power source to the computer, this stops. And with power connected this 'white noise' does not come through the laptop speakers or headphones if plugged in.

I realise this must be an earthing issue, and there is a GND connection on the amp. How do I go about earthing my laptop in this way?

 

[emcc_3]

the power supply is interfering with the amp.

 

[Anonymous]

As the second poster said the laptop's noisy switchmode PSU is doing this.

A trick that I have found usually to work pretty well is to fit a 1:1 240V isolating transformer (NOT an auto transformer) between the laptop PSU and the mains. You can get these from professional suppliers like RS and Farnells or maybe Maplins. There are a couple of bigger ones on e-bay right now for about £40.

Alternatively you can try an outboard DAC using an optical digital connection, assuming your laptop supports this.

HTH,

John Dawson (Arcam)