Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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Re: AC Balanced Supply / Noise Filter: Jon Risch?

209.215.72.188

Posted by Jon Risch on May 13, 2000 at 22:30:53

In Reply to: AC Balanced Supply / Noise Filter: Jon Risch? posted by Allan Moyse on May 13, 2000 at 18:29:12:

Low frequency AC line noise is the hardest to get rid of, especially if you don't want to affect component dynamics. My DIY AC Line Filter does an excellent job of filtering RFI riding on the line, and HF hash, but is limited in how much LF line noise it can filter. Since the cost is so low, you would not be out a lot if this did not do the full job. It should provide some help, and in general should sound better, perhaps in other ways than merely reducing this obvious noise source.

The isolation transformer will probably provide more LF AC line noise reduction, and this approach should give you about 10 dB less noise.
If combined with the DIY AC Line Filter, you may acheive enough noise reduction to be able to fully enjoy your system. Note that the balanaced power approach may not provide any extra noise reduction over a simple isolation transdormer. Since it is your preamp that seems to be the most sensitive, perhaps just a reasonable sized isolation transformer for it would be the first thing to try.

It might help to keep in mind that most of us seldom us all the available gain in our systems, and if you normally listen at -36 dB or so, then you could think of your system as having 36 dB of gain headroom, nd not worry too much if noise becoime saudible at full up (0 dB). I would say that if -36 dB is typical, then if you crank the gain up to -16, or 20 dB over normal use, and the noise is not a big factor at this gain, then you would have reduced it to the level where it should not interfere with your musical enjoyment.

Jon Risch

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