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Originally Posted by Jammin72 /img/forum/go_quote.gif
OK I need to study that a bit, equations aren't my strong suit these days.
Seems like you have studied it, I saw a couple of other responses by you as to this subject.
What exactly is the AV710 putting out of the line output power wise?
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I only studied it as an elective
but here goes.
You know those spring-loaded doors? The ones that close by themselves? Well, a door with a low damping ratio (or damping factor, as they sometimes refer to it) will swing back and forth for a while before closing (assuming there is no door stop--if there is one, it will just slam into it). A door with a high damping ratio will start closing, but as it comes to its goal (which is being shut) it will slow down precisely and close smoothly and quietly.
Well, electric waves are somewhat like the door swings. Take a look here:
http://www-math.mit.edu/daimp/DampingRatio.html
The 10, 1, 0.1, 0.01 buttons are for scaling the top graph. At the bottom, the middle slider (with green "zeta" letter) lets you control the damping ratio. Notice that as the absolute value of zeta decreases (as you move it to the right), you get more "waves" on the graph. That's more swings of the door or, in case of electric waveform, more parasite harmonics (which are 2x, 3x, and so on of your current signal frequency). A system with low damping ratio will havee very high THD (total harmonic distortions) coefficient, among other things.
How is damping ratio of our systems calculated? I am not an EE major, but basically it's the impedance of what you are driving over the impedance of your output. Now, AV710 is designed to drive line inputs. Their impedance is usu. 50 - 75 KOhm, which is incomparable to headphones. It's safe to assume that the output impedance of AV710 is fairly high--even if it's e.g. 500 Ohm, we still get a damping factor of (50K or 75K)/500 = (100 or 150) on most inputs, and that's actually a very good number. But what if our load impedance is low? E.g. we connect Audio-technica or Grado headphones to it? Well, the damping factor goes way down, probably below 1. You can see what happens to THD in the interactive demo I linked to. That doesn't mean it won't go loud--it will. AV710 drove my AT's to unlistenable volumes. But the sound was EXTREMELY "dirty", as if I plugged in a very cheap electric guitar into a very bad, semi-functioning amp and switched to "distortion" mode.EDIT: Well, OK I'm exaggerating a bit--but the sound was not clean, and it was VERY easy to hear.
I hope I didn't confuse you further. But it's always funny when people say "Grado/Audio-technica are easy to drive". They are easier to get loud, sure. They are not easy to drive properly.
