|
Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
|
|
|
Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
|
In Reply to: Current drawn from mains supply posted by guyser on April 21, 2006 at 15:45:45:
"When an amplifier is playing I can understand that the current draw (in most instances)will vary depending on how hard it is working. However do these increases in current only get drawn at the supply frequency ie 50 or 60 Hz or are there higher frequency elements to the current being drawn?"The power supply's "filter capacitors" get charged at double the line frequency. A "full-wave" rectifier inverts the "negative" half of the incoming sine wave, hence the rectifier "charges" the filter capacitors 100 or 120 times per second. The music signal draws current from those filter caps, which ideally should not discharge appreciably "between the rectified peaks." But in the real world, such discharge is unavoidable (unless regulation is utilized), and the rate of discharge is a function to both filter cap size and the power delivered to the speakers. (But with larger caps, it also takes longer for the transformer/rectifier to restore the charge.) So during high power delivery to the speakers, the output signal actually modulates somewhat at double the mains line frequency.
A good test for this is to play a noise signal at or near the amp's rated power. (This implies the signal is driving a "speaker load.") There will be a "spike" in the noise spectrum at 100 or 120 Hz (and maybe harmonics of that), and that spike should be of course as low in amplitude as possible, relative to the remaining noise signal. The lower the spike amplitude, the "stiffer" the power supply.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: Current drawn from mains supply - Todd Krieger 23:52:53 04/24/06 (1)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
