Originally Posted by Chris J
Brothers and Sisters,
Let us bow our heads and calculate...
Take a 6 ft. power cord with 10 pF/ft of capacitance and 0.155 uH of inductance. It may have a name like, um, Nordost Bue Heaven.
At 1 MHz this is XL = 5.84 Ohms and XC = 2653 Ohms.Very interesting....
Yes, but if you read what I wrote above, I asked "how much will a power cord pass at 1GHz?" That's because I had to go up to 1GHz to get something resembling a short circuit for the given diode capacitance.
The real thing to keep in mind is that HF noise still breaks thru a garden variety PSU if you do not take action to prevent conducted HF noise, i.e. board layout, lead dress, appropriate capacitors, etc.
The noise doesn't break thru only when the rectifier diodes are switched on.
No, it doesn't. But the charging current to top off the reservoir capacitors does, which was the point I was making in my original post before I let myself get sidetracked with the RF issue.
In fact, the rectifier diodes switching on and off are part of the problem.
Yes. And that will be the case even with "perfect" mains AC and a "perfect" power cord.
Anyway, my main point about the power cord being out of the circuit the vast majority of the time IN THE CONTEXT OF IT SERVING ITS PRIMARY FUNCTION was that I find it so very curious that people describe the effects of power cords in the exact same terms that they do with interconnects and speaker cables.