|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
|
|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
In Reply to: Tube amp vs. SS amp clipping on high effic. speakers. posted by edta on September 22, 2001 at 17:09:09:
It is very simple... most solid state amps these days are class AB. That is, there is a split power supply, ground being 0 v, and +V and -V rails. There are power transistors, one for the + half of the cycle, one for the - half.When the class AB amp reproduces a signal, one transistor turns on when the signal is positive, and when the signal is negative, the other transistor turns on. There is a slight overlap in the middle, so that there is no switching distortion with very small signals near ground.
(OK, for you purists, Class A amps do not have this problem, but still clip in the same fashion. And get too darn hot.)
Now, let's look at the power supply. If the power supply is +/- 30 volts, the highest signal that can be produced is a few volts less than +/- 30v. This is due to loss through the output transistors and their drivers. So, for all practical purposes, the highest voltage the amp may produce is approximately +/-27 v.
So, along comes a signal that requires the output to be 32 volts. Well, that voltage is simply not available... the power supply is lower than that. So, the transistors go as high as they can (in this example, +/- 27 v), and that is all they can do... Whatever is above that voltage level is lost, the top of the waveform is simply flattened. Thus it is said to be "clipped", and if the wave is a sine wave, of very high signal input, and clipping is severe, the output waveform approaches a square wave.
Now it no longer sounds like a sine wave, which is very pure, and has no overtones. Now it has odd overtones, which is necessary to form a square wave. And these overtones (yes, up there in the corners of that "square wave") are of a fairly high percentage of the output signal. So, this high frequency, high energy simply goes straight to the tweeter, burning it out usually.
With tube amps, these corners are rounded off due to the characteristics of the output transformer, and the way a tube amp works. So, those corners are rounded off more, and the resulting tone is mellower... having some even overtones, too. The clipped wave, once it gets to the output, is a rounded off sawtooth wave, and is mellower sounding.
Perhaps someone else can explain what happens when a tube amp clips better than I, but all transistor amps are going to clip in the way I describe above. One brand of SS amp is not going to sound any better than another.
OK, you Golden Ears out there, I will say it, I highly doubt you can hear less than 1% distortion, etc. As long as the amp is not clipping, no problem. And distortion will be very, very low.
Aside:One advantage of biamping... It will always be the low frequency amp that clips, as 90% (well, sort of... ) of the power is in the low end. So, this clipping results in high frequency signal... but the woofer is not capable of reproducing this. The tweeter, being on a separate amp, and not clipping, is not getting any distortion. So, a cool thing happens... when a high level signal comes through the woofer simply limits somewhat, and the tweeter keeps singing along unaffected. You may not even notice there is any distortion.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- How amps clip - Paul C. 09/24/0119:35:27 09/24/01 (1)
- Re: How amps clip - can SS be made to fake tube? - freddy 21:57:44 09/24/01 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
