Reversing absolute phase

Reverse the speaker cable leads at either the amp, or at the speakers, but not both. This reverses absolute phase (as opposed to having only one speaker wired backwards, which results in the speakers being out of polarity...something which is sometimes mistakenly referred to as being out of phase).

Some tube preamps invert phase, which requires the leads to be swapped at the amp or speakers, unless the preamp has a phase switch.

Here's a more complete explanation from Galen Carol Audio.

The nice thing about this tweek is that it costs nothing, and will keep you occupied for several hours!

Thanks Tvad!!