03-20-14: Mapman
Al, explain please why that would not be useful?
Hi Mapman,
I think oscilloscope measurements would be unlikely to be useful because:
(a)The noise and distortion that is present on the AC will consist of a complex and probably time-varying mix of essentially ALL frequencies extending far up into the RF region, at many different amplitudes, including broadband noise as well as noise and distortion components at discrete frequencies. Most likely the amplitudes at some of that near-infinite number of frequencies will be higher after the change than before, and some will be lower after the change than before. There's no way to predict how a specific component in a specific system will react to that complex mix of differences.
(b)An oscilloscope won't provide much if any detail about that complex mix of differences anyway. It will pretty much just give an indication of the amplitude of the overall sum of everything, and perhaps also the amplitude of SOME of the discrete frequency components. Whether that overall sum is more than or less than what was present before would tell us little or nothing, because the sensitivity of the system components to noise and distortion at different frequencies within that sum will be different.
(c)There is also no way to predict whether ANY of the differences in noise and distortion that may be measured would have any relevance at all to the sonic changes that are perceived. How can we know, for instance, whether a small change in line voltage, a small change in contact integrity somewhere, the breakin possibility some of the others have referred to, or some other effect, will or won't be more responsible for the perceived change?
I learned many times over during my EE career that from a practical standpoint some things are inherently unpredictable, and can be determined only by trial and error. A good design will have as little sensitivity as possible to unpredictable variables, but no design is perfect.
Best regards,
-- Al