@mdalton I was intrigued by your exerts from the PSM156 review in ASR so I read it. My suspicion was confirmed, Amir tested the device with one piece of hifi gear attached at a time. My understanding is that higher end power conditioners have several functions: to supply non limiting current to a number of devices simultaneously, to filter noise that may be in the AC supply line, either coming through the mains at the breaker or imparted to the line between the breaker and the outlet, reduce noise in AC lines emanating from the attached gear or power cables, and potentially surge protection. In Amir’s test, he looked at the performance of the Puratin device with respect to noise in the AC supply line and looked at the measured performance of one piece of attached gear.
Hifi systems in practice can be quite complicated, with multiple devices connected to a power distributor/conditioner. For example, my system is a hybrid 5.1/2.1 home theater and two channel system with four different sources, both digital and analog, a large receiver and a subwoofer. Power from the 20 amp breaker is supplied by a single run of 10 gauge romex to a medical grade outlet. I have a stacked rack arrangement with seven different power cables and fourteen different lower level digital and analog cables all in rather close proximity. Most of my power supply cables are upgraded except for an old Blu-ray player and a vintage turntable which have attached “lamp cord”. The receiver is plugged directly into the wall and everything else is plugged into a power conditioner/distributor. I suggest the opportunity for some electrical noise generated in digital devices or power supplies to affect other devices or cables nearby is significant.
My system definitely benefitted by replacing a sturdy but simple non-surge protected power strip with a more substantial power conditioner/distributor, and by again by replacing the supply cable from the wall to the conditioner/distributor with a better cable (the single biggest cable improvement I have made in over 20 years of tinkering). I do not know if this benefit of adding a new conditioner/distributor and supply cable had to do with less current limitation due to higher gauge internal and external wiring, cleaning up AC from the mains, or reducing the impact of noise generated in the attached equipment.
What I do find challenging is a review of a power conditioner designed in part to tame electrical noise in a system of attached components by connecting and assessing one device at a time. The review of the Puritan Audio PSM156, perhaps more than any other on ASR, points to the weakness of the reductionist approach for evaluating products that were designed to reduce noise and improve the sound of a complex system by looking at one variable in isolation. To strain the oft used audio-car analogy, this is like saying “I tested the Corvette on the skidpad and while it did what the manufacturer claims I cannot recommend it for driving in traffic”. This also reinforces the need to test equipment in your system in your room with your ears. No two circumstances are alike, and as always, YMMV.
kn