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What a coincidence!

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In Reply to: RE: Dealing with hum and a PPP posted by watch'emglow on June 23, 2009 at 06:38:09

Hi watchemglow. I have come around to looking at power improvements again as well. You might recall that we were looking at our same respective issues at the same time about a year ago. Did you manage to reduce your input THD?

Follow Ups:

RE: What a coincidence! - watch'emglow 18:32:45 07/22/09 (3)
Hi Amdan,

Yes, I had a pretty major win about 6 months ago - I've been meaning to post about it since but haven't got there yet. When I first moved into my current home, over six years ago, I couldn't (and didn't) listen to the hi-fi at all because it sounded so awful. After nearly a year I bought a PS500, which improved things dramatically. The only problem was the fan noise which seemed to get progessively worse over time. Eventually I upgraded to a PPP - it took me three units before I got stable one, but my current one has been pretty good. I was a bit disappointed to find nightly variation was worse than it had been with the P500, that my components were humming (which they hadn't with the P500) and that my THD improvement was mediocre - which, from what I understand, is probably due to having a sizable voltage differential to overcome.

Anyway, frustrations at this point prompted me to go back to my electricity supplier. I'd tried this in the past and not got very far, but this time I must have found the right person on the right day (and using terms like harmonic distortion helped, I think) and they agreed to send someone out to put a power quality monitor on the three phases coming into my house. When they guy returned the following week he said that one of the connections hadn't been true and they only got readings on two of the three phases, both of which were OK, showing distortion readings of about 1.5%. But he suggested sticking it up for another week to test the third phase. He came back a week later with a cherry picker, two support vans and four blokes. The third phase had shown about 5% distortion - the top of their acceptable limit.

They traced the phase back into the house and, sure enough, this phase was feeding the loop that the hi-fi sits on, so they spent an hour and a half playing around with the connections and putting the hi-fi on the cleanest phase, all free of charge. Normally they wouldn't touch anything on the home side of the point of common connection, but it is obviously cheaper and easier for them to do what they can in these instances than it is to deal with the problem at its source.

The outcome has been a marked improvement in the sound itself, and in the night by night consistency of the sound (still varies, but overall much better). Incoming THD is lower and, therefore, so is that passed on to the components. I've since been able to identify (and to some degree, rectify) phase anomalies in my speakers, and introducing some Boston Audio Tuneblocks (vibration absorbing footers) has brought clear benefits. Previously it would have been a rare night of power quality that would have allowed me to hear these differences.

I still get hum from my components and I'm in the process of looking into this now. Humbuster is an option, or I'm considering an isolation transformer which can also trim 20V from my AC, thus making it easier for the PPP to do its job properly. Cawsey (based in Melbourne), from whom I get my cables, are helping me look into the latter. Apparently, apart from voltage, there are other fundamental differences between US and Australian mains supply, such as independent floating of Neutral and Earth. As such, a home-baked solution might not be a bad thing.

Sorry Amdan if I've been a bit long-winded. In a nutshell, if your incoming THD regularly shows above, say, 4% you should consider asking your retailer if they can monitor the incoming power quality. If your PPP or components are humming, then you might like to see how I go with my solutions.

cheers,
- RE: What a coincidence! - amdan 22:22:38 07/26/09 (2)
  Hi. Thanks for the post. I am very interested in any improvements you make. My input THD is less than 4% so I guess my power supply is ok. I have noticed that the sound quality is much better in the mornings than at night. I presume at night my neighbours are using their various pieces of electrical equipment hence a deterioration in SQ.
  Please let me know how the humbuster works for you. Also, have you tried improving your ground? I have heard that this can help significantly.
  - RE: What a coincidence! - watch'emglow 04:45:44 07/27/09 (1)
    Actually, I've just tried a tweak, practically free, that really has me shaking my head in disbelief at the improvement it has made. Give me a few nights to confirm I'm not fantasizing and I'll give you the details. Might be better by email actually.
    
    Never went down the dedicated line and dedicated ground path, mainly since I'm renting, but also couldn't find an consistent opinion on the benefits - some even suggested it wasn't legal to do so.
    - RE: What a coincidence! - amdan 01:17:20 07/28/09 (0)
      I am intrigued. I look forward to your email.

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