|
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: RE: Distortion and Audibility...replay. posted by morricab on June 18, 2008 at 00:39:40:
"Does this mean that these were the distortions below clipping and that 3% of the samples were clipping?"
Yes, I think that is what he is saying.
I went back through the article again to try to figure out what his "alpha" parameter was, and I think I have it now. In the figure below, vref is the peak value of the input voltage (x-axis) for the solid-state amp (red trace below) that will just cause it to clip. It's a bit confusing because the amp shown is inverting.
Next, he defines a parameter "alpha" equal to the ratio of the RMS value of the input voltage to the reference voltage vref defined above. See the plot of sine wave distortion below. The solid-state amp model is again shown in red.
Note that the distortion for the solid-state amp model is zero (minus infinity dB) for alpha less than 0.707. Since the RMS value of a sine wave is its peak value divided sqrt(2), this is consistent with the definition above. Another way of looking at this is to say that the RMS value of the input voltage times the ratio of the peak-to-RMS voltage (sqrt(2) in this case) must be equal to vref at the threshold of clipping of the solid-state amp. Thus alpha = VRMS / vref = 1 / sqrt(2) = 0.707 at the clipping threshold.
Then he mentions that for two different music selections, the ratio of the peak power to the average power is 38:1 and 82:1. The ratio of the peak voltage to the RMS voltage is therefore the square root of that.
Let's take the 82:1 case. The ratio of the peak voltage to the RMS is sqrt(82). So VinRMS * sqrt(82) = peak voltage = vref to give clipping. Thus alpha = VinRMS / vref = 1 / sqrt(82) = 0.11 at the clipping threshold. For the 38:1 case, alpha must be 0.162 at the clipping threshold. For any alpha values greater than the clipping threshold, some percentage of the samples will be clipped.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: Distortion and Audibility...replay. - andy_c 08:19:58 06/18/08 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
