Measuring line noise and power conditioners

A minor correction to my previous post: In the first paragraph when I said:

"... when the instantaneous voltage of the incoming AC waveform exceeds the voltage on the storage capacitors by the small amount that is sufficient to turn on the rectifier diodes."

I should have said:

"... when the instantaneous voltage of the AC waveform at the output of the power transformer exceeds the voltage on the storage capacitors by the small amount that is sufficient to turn on the rectifier diodes."

That applies, btw, to both the positive and negative peaks of the AC, assuming (as is usually the case) that "full wave" rectification is being used

Regards,
-- Al

Conventional filters will do little in actual power lines or may even amplify EMI - it is in their own specification (that is, for those manufacturers who bother to publish such specification).  For a brief explanation please see this link:  https://www.onfilter.com/real-life-filtering    In short, regular filters are designed to perform at 50 Ohms termination (in and out) for EMC Compliance - CE and FCC.  I personally haven't met a power line with 50 Ohms impedance.  In real-life applications a better impedance ratio is 1/100 or 0.1/100 (not a critical difference in reality) where 1 or 0.1 is output impedance of AC power and 100 is rough number for a load, i.e. your amplifier.  It is imprecise but much more realistic than 50/50 Ohms. Since a filter is a combination of inductors and capacitors, when designed with one goal in mind to work in a 50/50 Ohms environment, this is where it "tuned" to.  In actual use it either does nothing or amplifies noise.  Our company (tooting my own horn here) designed filters for actual installations that we provide to the factories around the world, NASA, governments, hospitals, etc. - they are impedance-independent and essentially kill emissions anywhere they are plugged in -  https://www.onfilter.com/ac-power-line-emi-filters

OK.  BLATANT ADMISSION.  I am the manufacturer of the UberBUSS power conditioner.  This being said here is the experience of one of my clients:  Thread is on Audio Nervosa-

Check the new UberBuss with my Entech Wideband AC Noise Analyzer.

Calibraded the meter for a noise level reading of 100 on an AC outlet without the UberBuss plugged.

Plugged the UberBuss into the outlet and the noise level dropped to 50, plugged meter into the NCF outlet on the UberBuss and it dropped to .3.

Guess it works.