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Theory

Posted by Jon Risch (B) on May 29, 2007 at 19:30:21

In Reply to: RE: The maximum impedance of the 193H is at 5 KHz. posted by pmkap on May 29, 2007 at 08:08:32:

As far as I can see, the placement of the inductor across the line provides a low impedance at frequencies lower than the 60 Hz power line frequency, thus, it would attenuate low frequency disturbances on the AC power line below 60 Hz, with it's DCR the impedance at "DC".

While this may seem trivial, it helps to remember that almost all AC line filters, including my own DIY AC Line Filter & SS, filter out the HF's, and do nothing to the frequencies below some cut-off frequency. In the case of my AC Line Filter, it starts to cut-off up near the top of the audio band, depending on the exact source and load impedance.

As for how much AC power line content there is below 60 Hz, this is entirely dependant on your local power line conditions, and it is not uncommon for there to be residual "DC" present on the order of a volt or two, as well as frequency components between DC and 60 Hz. Most of those are the result of industrial equipment, unbalanced loads, and poorly designed and implemented power supplies that are sharing the AC line with your stereo equipment, esp. switchmode types. In a "perfect world", they wouldn't be there, but hey, we live in the real world, where Murphy thrives and rules.

Given that many of the classic audio components that are highly regarded for their sound also can have very simple/basic power supplies, and may be the most susceptible to LF AC line garbage, it would not be surprising to find that filtering out/attenuating those lower frequencies could provide a sonic inmprovement.

Whatever the choke does for HF's or RFI would be in addition to it's benefit at frequencies below 60 Hz.


Jon Risch

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