Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

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RE: Perhaps I should more clearly stated my point

Posted by Ugly (A) on May 11, 2008 at 18:47:25

In Reply to: Perhaps I should more clearly stated my point posted by E-Stat on May 11, 2008 at 16:54:56:

"The sins to which I refer are the various sources of noise generated back into your AC line by all sorts of digital devices that live within modern homes like computers, routers, access points, DVD/CD players, TiVOs, mobile and cellular phones, etc."

I understand what you are saying however I disagree that this is an internal issue when you are talking about noise from a another device on the power line not even the device under test. As you point to, we are talking about waveforms which are conducted "BACK" onto the line which therefore will mix in with the AC power signal supplied by the utility to create something other than what was intended to be sent by the utility. The ripple induced back on the signal supplied by the power company due to things like back emf from switcher coils and the regulation issues caused by having a highly variable load impedance in the form of the input to a switching power supply at the end of an impperfect transmission grid are generally not going to be a problem for the device with the switching supply causing the problems due to the fact that these switchers will have a control frequency granularity well up out of the audible range and therefore very succesfully filter these types of issues out of audio signals but it will be a huge problem for other devices with circuit topologies that aren't so adept with these types of waveform anomalies and end up mixing these ripple noises into their own audio signals. The types of equipment very susceptible will be the standard audiophile gear employing a good old fashioned linear power supply which due to cost cutting may get trimmed to low iron/copper winding content transformers and tiny little filter capacitances and low cost off the shelf linear regulators which when taken as a whole power supply circuit are simply incapable of filtering the problems. The point is that whether the problem comes from the device sitting next to the device under test or the neighbors house or some device accross town it doesn't really matter since once it is "BACK" on the line it is a grid issue not an internal one.

"The problem with your experiment is that it assumes there is only one variable - the grid - which is not the case. Regardless of the quality of the grid, there is always a difference in my environment due to internally generated noise."

Rather I see my experiment as well enough thought out to isolate the effect which I am intending to study. I think if you read back throuh my post you will find that in no way have I denied that noise and distortion due to internal circuit problems don't exist. On the contrary I have merely been attempting to keep a discussion about apples off the topic of oranges.

This post is made possible by the generous support of people like you and our sponsors:

Atma-Sphere Music Systems, Inc.

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