What I am going to say here is based on 30+ years of experience with major manufacturers (GE, SqD) and a utility (Ga Power)in the electrical products market, from the high voltage switchgear utilized by the utility all the way down to the 15 amp circuit receptical (outlet) in a residence. During this entire time I have maintained a strong interest in audio, although I have only recently invested in big buck gear. 1) I never heard ac noise in my audio system until I had purchased the big buck gear that revealed the power quality for what is is! 2) The dedicated circuits and isolated grounding that I am using is effective, up to a point, in reducing the problem, as follows: a) from my listening position, I have dead silence 98% of the time. The 2% that I don't is due to feedback via the common (neutral 'white wire') from my PC, a dimmer, a fluorescent lamp, & sometimes the refrigerator, all inside my own house & not the utilities problem. b)for this 98% 'Quiet tTime', if I get down on my hands & knees & put my ear 1 to 3 inches from the bass drivers, I can hear the 60hz 'thrum-thrum-thrum'. This is when my tube power amps are on, regardless of preamp on or off & regardless of the amps being fed via preamp or direct from the CD source. The 'thrum' is less when using cheaters to eliminate the ground all together than without them, but either way, to hear it, requires being on hands & knees very close to the bass drivers. c)none of the AC power devices I've tried have done anything to reduce this 60 hz 'thrum'. Exotic power cords don't either, although they seemed to do more on the non- dedicated circuits I had before. I have delt with wiring devices, from the 29 cent outlet variety through the most expensive mass produced ones by Hubbell, P&S, Leviton, Bryant, etc, & have heard no difference until the point where the cheap ones lose their spring tension & cannot hold a plug tightly. I use $8.50 P&S isolated ground industrial grade 15 amp recepticals fed by # 12 20 amp solid house wire, individual wires, not romex, in a steel conduit. d)I have not tried the PS300/600 yet, as the 'thrum' I'm describing is of such low level it is completly hidden by any level audio signal. However, the product makes technical sense as it delivers balanced ac power to our North American 120 volt homes. 240 volts is balanced, 120 is unbalanced, which allows the neutral feedback I mentioned as the source of my 2% problem. I would love to hear from some of our European readers about line noise in their 240 volt systems - I bet it is far below the audible level - but I don't know from experience. If it is, we can all have 240 volt dedicated lines installed & buy 240 volt gear! 3)The 8' ground rod outside my listening room that I use to ground my dedicated circuit is not strictly in accordance with the National Electrical Code, which insists that the ground path go directly back to the service entrance box. There is a safety reason for this NEC requirement, in that if you somehow manage to get hold of your service entrance ground at the same time you have a hold of your dedicated ground, you can receive a shock from the difference in ground potential, so if you do this at home, know what you are doing! I'm not recommending it to anyone else just because I do it, remember I have an electrical background. 4)Anyone know if the PS300/600 solves this problem? Any other solution? Thanks!!
