About a year ago, a storm destroyed several transformers near my house. The power company replaced them and subsequently, I noticed "noise" that I believe was not present prior. I purchased a 156 and plugged everything (amps, preamps, Dac, SoundSmith strain gauge cart ) into the unit. I noticed a marked improvement in the noise level, better clarity, etc. I A/B'd the unit with plugging everything into the wall (dedicated 20A circuit, whole house surge protector) and felt that the 156 was an improvement. My preamp and amp (mono blocks) are tube based which might make a difference.