[linux-audio-user] noise from USB printer

[Dave Phillips]

Pieter Palmers wrote:

> Is the noise only present when printing, or also when the printer is 
> idle?

Noise is there whether the printer is turned on or not. It disappears 
only when one or another of the cables are disconnected.

> What you can do to test whether it is a ground loop is interrupting 
> the ground connection of the power plug (e.g. by wrapping some 
> non-conductive tape around the pin). If the noise stops, you have a 
> ground loop. Don't use this as a solution to your ground loop however, 
> as it is probably against regulations and is also pretty unsafe 
> regarding electric shocks.
>
> If it is a ground loop, it is pretty difficult to solve. It's badly 
> designed hardware. You could try to plug your printer into the same 
> power outlet as the machine.

The printer is plugged into the same strip as the machine.

I tried lifting the ground, the noise was undiminished.

Next I'll try reprioritizing the interrupts, as soon as I can get 
irqtune built. Or is there other software I should try ?

Linux 2.6 kernel, Debian Etch.

Best,

dp