Maybe this note from Roger West will be the last word in Power Cables for SoundLab Speakers.
Hello Eric,
The major work that we have been developing is a bias supply that uses a miniscule amount of the audio power from the amplifier to develop the bias voltage. This eliminates the AC power cord, but does not have any effect on the sound quality. The major reason for the development is to eliminate the challenges of different voltages and connector types in foreign countries. Further, it eliminates problems with importing speakers that use AC power, which usually requires an inspection. If you do not mind using an AC power cord then the self-bias approach would be of no value.
Other than the self bias development we have not made any changes since you purchased your speakers 4 years ago.
I think the operative words are “miniscule amount” of power required.