Home Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

[ Follow Ups ] Thread: [ Display  All  Email ] [ Propeller Head Plaza ]
[ Alert Moderator ]

Re: You are dead wrong....as usual

"Looking back into it, it is effectively a dead short against back emf"
The circuit as a whole perhaps but not the transistors themselves. THese will behave like a very high resistance to back EMF shunting most of it through the feedback loop because that is a lower impedance pathway. This is probably why the impedance "looks" lower to the load. A transistor has low impedance in only one direction, Soundmind. If there is no feedback, then the energy is turned to heat in the transistor because it has nowhere else to go. I think the feedback loop is absorbing the energy not the transistor.

This could probably be measured on an oscilloscope by hooking an amp up to a highly reactive load, putting a clean sine wave through, and then measuring the signal at the point the feedback loop connects to the input. Then take the reactive load off and put a pure resistor on the end of the amp and measure again. Then you would know if the back EMF gets back all the way to the input or not.

You are looking at it as a black box and not how each component is playing a role. Dan's post from audioholics shows that it doesn't appear to be a motor control issue with even modest damping factor. Debunked. So the only reason left is lowering distortion, right or perhaps amp stability for those marginal designs.

Look at the post I made to Dan with all of the plots of high feedback amplifiers. I direct your attention to the damping factor vs. Frequency. Notice that the damping factor on these amps drops precipitiously above about 1Khz(sometimes lower sometimes a bit higher). Now look at the THD vs. Frequency. See the rise that nicely mirrors the damping factors drop? Some of these amps have 100x more HF distortion! Clearly the feedback control is starting to slip when the damping factor drops and this is reflected in the THD rise at HF. Can't be good for sound, can it? Or do you say its inaudible so why worry? Even Dan won't say that, which is why he goes to pains to say his amp makes only 2nd harmonic, which I am very skeptical of, BTW.

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

Follow Ups Full Thread
Follow Ups
You can not post to an archived thread.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]