This post was inspired by answering a question about power conditioners.
In reviewing the Puritan Audio PSM 156 on ASR, the author says "as always, we attempt to tease out the transfer function of the conditioner using normal audio level signals" and after many measurements with test signals concludes with "as you see, I have run a number of tests to give the PSM156 ample opportunity to show it can do something to improve audio but it can’t even move the dial one hair. There is no indication or logic that would tell us that it can make an audible improvement."
It is important to note that at no point was it mentioned that music was played through a system with and without the PSM 156 in the circuit. I don’t spend my hours of relaxation listening to test signals - I listen to music. The ASR review failed to assess the impact on music reproduction.