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Old 15th November 2007, 06:56 PM   #1
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Default Power Conditioning

I was listening to some music the other day and I noticed that all my transformers were humming. It was even audible from the speakers and such. My good old ISObar buzzes too. Dirty power? I know my power is dirty, no doubt, but would that cause my transformers to buzz like that?

So how about using an industrial power conditioner? I can get a Oneac 2228 used pretty cheap and rewire it for 120ish voltage. It can do 24 amps! 100lbs of isolation transformer madness! Cleaner power or just a boat anchor? I figure with such high capacity the impedance should be low.

Would a big 1:1 isolation transformer clean up the power enough or is it necessary to regenerate AC to DC and back to AC?

Has anyone tried using a larger battery based UPS?
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Old 16th November 2007, 06:20 AM   #2
Eva is offline Eva  Spain
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Toroids will humm either when they are saturating due to a too high line voltage (100/120Hz noise) or when mains voltage contains some DC (50/60Hz noise). Try to identify your problem first, simple DC filters make wonders if the problem is DC.
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Old 17th November 2007, 06:30 AM   #3
ssmith is offline ssmith  France
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I had a similar problem with DC on my AC causing toroidal hum, and used a DC filter from diyaudio member PerAnders, which is very simple and solved problem. The schematic is super-simple, though I'd recommend his PCB as it is very well made.

Would be worth checking first if it is DC on the mains that is causing the problem. In my case, I don;t have DC on the mains all the time, but only when things like ceiling fans are switched on. Then my toroids start to hum.

For a UPS to be an improvement, I believe you'd need an online UPS that puts out a pure sine wave and sufficient current capacity. Most (cheaper) UPS's are off line, which means they only regenerate when the AC is cut, and would therefore to nothing to clean up your power. Even then, many (cheaper) online UPS put out a 'modified' sine wave -- which may turn out to be worse than your mains.

I also use an IEC inlet that filters EMI/RFI. Some people don't like to use these, although where I am they result in a lower noise floor.

I have never tried an isolation transformer.

I'm sure other (far more experienced) people will be able to chip in and correct me if I've said anything wrong.
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Old 17th November 2007, 01:13 PM   #4
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Without testing I would be sure that there is DC on the line. My house is old and the circuit is poorly done to todays standards.

A friend of mine mentioned that he used an isolation transformer as well with good results. Power here is very dirty I guess. A good one resolves voltage fluctuations, spikes, and noise. It does add some impedance though, but at over 20amps I don't think there would be any significant impact.
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Old 3rd December 2007, 06:17 PM   #5
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If you have a constant hum it's probably not DC that is the problem. Is the transformer a toroid transformer?
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Old 28th December 2007, 03:06 AM   #6
jborum is offline jborum  United States
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It's overpriced, but check out this product:

PS Audio Power Plant

It's basically a huge amplifier that creates a 60hz sin wave with optional harmonics, converting your power to DC and back to AC again.
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Old 15th January 2008, 08:42 PM   #7
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I've got a Hammond 274BX that buzzes once it reaches load. It gives off an awful lot of EMF which gets picked up by my preamp and turntable. My marantz 8b does the same, as well as my TV. It all runs through an old IsoBar power strip that should have some filtering abilities.

I've got my hands on a big honking Oneac ccs-2228 power conditioner, but it's rated for 240V instead of 120V. I'm not sure that it will work correctly on 120V. On it's innards it has a large transformer with dual primaries and secondaries that are currently in a series configuration. The ccs-1128 which is the 120V equivalent is wired in parallel. The surge protection, and ferrite section could probably be bypassed, but I'm not sure what the implications are for that. The documentation on the oneac.com website isn't very detailed.
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Old 23rd January 2008, 03:11 PM   #8
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I've traded in the big power conditioner for a tiny 120V 1A isolation transformer.

When I plug my amp into an isolated mains circuit, there is no noise at all. Putting a Tripp Lite IsoBlock inline causes a mess of buzzing on the amp side. The isolation transformer doesn't appear to do anything useful so far.

My guess is that the IsoBlock/IsoBar create more noise than they filter. Ironic? More experiments tonight...
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Old 28th January 2008, 11:38 PM   #9
huy5005 is offline huy5005  Canada
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There is an article by Thorsten Loesch.
You can take a look it's simple and very effective

http://www.tnt-audio.com/clinica/mains_e.html
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Old 29th January 2008, 02:42 AM   #10
KSTR is offline KSTR  Germany
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Quote:
Originally posted by jborum
It's overpriced, but check out this product:

PS Audio Power Plant

It's basically a huge amplifier that creates a 60hz sin wave with optional harmonics, converting your power to DC and back to AC again.
Just for the record, that's what the older PS-Audio devices did. The new one (Premier) is a piggyback type of circuit, a corrective amp "on top" of the existing AC. The frequency is always in sync with the actual mains frequency.

- Klaus
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