High pitch squeel comming from speakers

[robcheese]

Hello,

I just got a Lepai LP2020A+ amp and hooked it up to a pair of Mirage M-90i speakers. Whenever the amp is on I can hear a faint high pitch noise (sort of sounds like a kettle boiling) coming from the speakers. Turning up the volume on the amp does not affect the volume of the high pitch noise. Hooking up an mp3 player to the amp also has no effect on the sound but if I hook up the headphone output of my TV to the amp the sound gets much louder and turning up the volume on the amp makes it even louder.

The amp didn't come with a power supply so I bought a 12V 3.3Amp regulated power supply for it. If I wiggle around the power supply's connection to the amp I hear a crackling noise and sometimes the high pitch sound will stop.

I tried lifting the ground on the power supply using a 3 prong to 2 prong adaptor and this totally got rid of the high pitch sound. Is this a safe solution? If not, any ideas on what is causing the problem or how to fix it.

Thanks!

Rob

 

[robcheese]

Just found out that my printer seems to be causing a ground loop. So if I disconnect anything in this chan the sound goes away: Power supply->Printer->USB->laptop->HDMI->TV->TRS Cable->Amp->Power Supply. However there is still a very quiet high pitch noise coming from the speakers and they make a loud popping sound when I turn on the TV.

I'm still not clear on what if anything is actually broken...