Due to space limitations my phono preamp sits on my cd player. I discovered that turning the cd player off reduces a very slight irritation to the sound. I remebered this today during a long vinyl session and the sound was putting me on edge. Trying to figure what was wrong I saw the cd player was still on. Turned the cd player off and it was back to the sound I love.

Of course if you have a phono preamp on it's own shelf or it is a better built, isolated unit this may not effect the sound of your system.