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In Reply to: RE: Class D , Class-a , Zmin and phase is Very important posted by morricab on February 27, 2016 at 15:38:04:
I suggest to perform a test measurement yourself. You'll need a spectrum analyzer, good 'scope, and obviously you'll need a Class-B (or an AB amplifier you can under-bias to Class-B operation) amplifier.
Output a high frequency sine wave at say 40 and 4 watts into a standard load. Let's say you measure 0.01% crossover distortion at 40 watts, then you would expect to measure 0.1% at 4 watts, yes? I guarantee you won't.
The reason is because your "flat spot" doesn't stay flat when you increase the output power level. This alters the relative distortion spectrum of the two different power levels and thus it's NOT frequency independent and not "constant." It's also why negative feedback can have a noticeable effect to reduce (not eliminate!) crossover distortion (better) at lower power levels, because in that case the harmonic content is concentrated more at low frequencies.
If the components used in said amplifier were all perfect....transistors with no non-linearities...no thermal tracking issues...bias solid....etc, etc, then you (and the textbooks) would be correct in your assertion. However, these are REAL-WORLD amplifiers and they exhibit numerous non-linearities and variables that skew them away from "textbook" results.
My primary "legitimate source" is my test bench. I've verified this.
Quit believing everything you read and start proving some of this stuff to yourself with practical experience and testing!
Cheers,
Dave.
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Follow Ups
- RE: Class D , Class-a , Zmin and phase is Very important - Davey 17:47:01 02/27/16 (23)
- RE: Class D , Class-a , Zmin and phase is Very important - morricab 14:32:22 03/02/16 (20)
- RE: Class D , Class-a , Zmin and phase is Very important - Davey 15:10:52 03/04/16 (19)
- RE: Class D , Class-a , Zmin and phase is Very important - morricab 11:46:38 03/06/16 (17)
- RE: Class D , Class-a , Zmin and phase is Very important - Davey 19:40:50 03/06/16 (16)
- RE: Class D , Class-a , Zmin and phase is Very important - morricab 03:59:28 03/07/16 (15)
- RE: Class D , Class-a , Zmin and phase is Very important - Davey 07:52:06 03/07/16 (14)
- RE: Class D , Class-a , Zmin and phase is Very important - morricab 05:18:52 03/08/16 (13)
- RE: Class D , Class-a , Zmin and phase is Very important - Davey 05:00:52 03/09/16 (12)
- RE: Class D , Class-a , Zmin and phase is Very important - Satie 21:05:36 03/09/16 (4)
- RE: Class D , Class-a , Zmin and phase is Very important - E-Stat 19:38:35 03/10/16 (2)
- RE: Class D , Class-a , Zmin and phase is Very important - A.Wayne 20:50:56 03/10/16 (1)
- Kinda - E-Stat 04:52:33 03/11/16 (0)
- RE: Class D , Class-a , Zmin and phase is Very important - morricab 08:17:23 03/10/16 (0)
- RE: Class D , Class-a , Zmin and phase is Very important - morricab 07:00:40 03/09/16 (6)
- RE: Class D , Class-a , Zmin and phase is Very important - Davey 18:47:39 03/09/16 (5)
- RE: Class D , Class-a , Zmin and phase is Very important - morricab 08:39:28 03/10/16 (4)
- RE: Class D , Class-a , Zmin and phase is Very important - Davey 13:15:18 03/10/16 (0)
- RE: Class B for the Deaf - A.Wayne 11:28:04 03/10/16 (2)
- RE: Class B for the Deaf - morricab 15:18:52 03/10/16 (1)
- RE: Class B for the Deaf - A.Wayne 20:37:15 03/10/16 (0)
- RE: Class D , Class-a , Zmin and phase is Very important - InfinityApogee 23:57:55 03/04/16 (0)
- RE: Class D , Class-a , Zmin and phase is Very important - InfinityApogee 20:07:42 02/27/16 (1)
- RE: Class D , Class-a , Zmin and phase is Very important - Satie 22:48:55 02/27/16 (0)
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