I should point out something you are not taking into account.
1) Guitar amps are not built to be hifi. There is often intention to build the amp to make distortion rather than to avoid it.
2) When any tube is driven, for example a power tube, the input capacitance increases with the drive. If the driver circuit isn't adequate to the task you will see crossover distortion in a push pull design. That is a design criteria; IOW a design flaw if the amp is meant to be hifi.
The video does not use much in the way of examples; your remonstration thus based on a logical fallacy.
We went round and round on this very topic on
this thread yet you persist. I put you on ignore for this sort of thing; since there are two problems, the first famously outlined by an American author named Samuel Clemens. The second problem is when you are presented with technical information, you simply ignore it. I am hoping this is not done out of malice but the alternative, by Hanlon's Razor, isn't great either. You can chose ignorance or you can chose to learn. Its up to you.
ESP - Description.
sound-au.com
Read this article. It disagrees with you about feedback improving zero crossing distortion. It also demonstrates why it is a bigger problem at low levels.
"The only point is to demonstrate that negative feedback can Never eliminate crossover distortion, because if both driver/ output devices are turned off, the circuit has no (useful) gain."
Most audio power amplifiers suffer from a defect known as "crossover distortion". This distortion is particularly troublesome at low output levels. At low power levels, the crossover distortion can rise to a high percentage of the output level and become the dominant source of distortion. The...
benchmarkmedia.com
"Most audio power amplifiers suffer from a defect known as "crossover distortion". This distortion is particularly troublesome at low output levels. At low power levels, the crossover distortion can rise to a high percentage of the output level and become the dominant source of distortion."
"Crossover distortion is particularly insidious in that it is not usually harmonic. The timing of the 0-current crossover events is a function of all of the frequencies being reproduced by the amplifier. This interaction causes intermodulation distortion (IMD) which is much more audible than harmonic distortion (THD). The distortion tones produced by IMD do not occur where our ears expect to hear distortion. IMD can cause two musical instruments to interact in a way that produces distortion tones that are never naturally produced by either instrument. For this reason, IMD sounds unnatural and unmusical to our ears."
"Crossover distortion can create fast transients that are too short to be corrected by a feedback network. The feedback network can actually extend the period of time over which the error occurs. Most class-AB amplifiers will show crossover distortion artifacts that have been stretched in time by ringing in the feedback network."
So, I don't agree with your assessment that crossover distortion is like other distortions that can be dealt with using negative feedback and it is independent of level, so it impacts low level signals predominantly.
This what I am talking about. Notice the top trace is the sine wave output and the bottom trace is the residual with the waveform notched out. You didn't do this, nor can you with an analog scope!
It's inherent in how transistors are non-linear in turn on and shutoff. Here are many examples of even so-called Class AB that have zero-crossing distortion. If you don't put enough bias then it is guaranteed to be there.
Sidebar 3: Measurements
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Sidebar 3: Measurements
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The Class AB mode for this amp has zero crossing distortion and the Class A mode does not.
Sidebar 4: Measurements
www.stereophile.com
Sidebar 4: Measurements
www.stereophile.com
Sidebar 3: Measurements
www.stereophile.com
Sidebar 3: Measurements For logistical reasons, I measured a different sample of the Dan D'Agostino Master Audio Systems Progression M550 monoblock (serial number PM006P) with my Audio Precision SYS2722 system (see the January 2008 "As We See It"). I repeated some of the measurements with the...
www.stereophile.com
Sidebar 3: Measurements
www.stereophile.com
Sidebar 3: Measurements
www.stereophile.com
Sidebar 3: Measurements To perform the measurements on the Plinius SA-103, I used Stereophile's loan sample of the top-of-the-line Audio Precision SYS2722 system (see the January 2008 "As We See It" and www.ap.com). As Erick Lichte listened to the SA-103 only in balanced stereo mode, I didn't...
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Again, AB has zero crossing distortion and Class A doesn't.
Sidebar 3: Measurements Before performing any measurements, I preconditioned the Classé CA-3200 by running it for 60 minutes at one-third power with all three channels driven into 8 ohms. At the end of that time, the THD+noise had dropped from 0.0024% to 0.00195%, but the top panel and the...
www.stereophile.com
As you can see, many modern amps suffer this problem even ones called Class AB. Probably only the Naim would claim to be Class B.
The amps that are Class AB and showing zero crossing distortion are ones where the bias has been set too low and they are not completely eliminating the zero crossing distortion as the transistors are now in a quite non-linear region of their transfer function. You can call this poor design if you want but it shows clearly what happens when the bias is set too low...exactly what you get in Class B. However, it is likely there is always residual crossover distortion unless you bias at full Class A.
Doug Self lists the 8 types of distortion mechanisms when he is discussing his "blameless amplifier"
TABLE 1.
SOURCE ORDER SLOPE ORIGIN
1 Input stage (balanced) 3rd-order 18dB/oct Inherent
Input stage (unbalanced) 2nd-order 12dB/oct Inherent
2 Voltage Amplifier Stage 2nd-order 6dB/oct Inherent
3a Output stage LSN (4 Ohm) 3rd-order 6dB/oct Inherent
3b Output stage crossover Complex 6dB/oct Inherent
3c Output stage switchoff Complex Variable Inherent
4 Non-linear VAS loading Complex Flat Inherent
5 Decouple return in ground Even Flat Topological
6 Rail induction Even 6dB/oct Topological
7 Wrong feedback point Even Flat Topological
8 Capacitor non-linearity Odd 12dB/oct Inherent
The distortions we have been discussing are distortions 3a, 3b and 3c, which he lists as "inherent", meaning they are fundamental to transistor function.
He then states: "In a field like Audio where consensus of any sort is rare, it is widely acknowledged that crossover distortion is the worst problem afflicting Class-B power amplifiers. The pernicious nature of crossover distortion is that it occurs over a small part of the transfer characteristic, and so generates high-order harmonics. Worse still, this range is around the zero-crossing, so it is present at all levels, the THD percentage potentially increasing as output level falls, threatening very poor linearity at low powers."
Furthermore: "To further get the measure of the problem, Fig 23 shows how HF distortion is greatly reduced by increasing the load resistance, providing further confirmation that almost all the 8 Ohm distortion originates as crossover in the output stage."
So, a typical loudspeaker load makes the situation worse and particularly at high frequencies. The lower the impedance, the worse it gets for a Class B amp.
Finally: "This leaves Distortion 3, in its three components, as the only distortion that is in any sense unavoidable, as Class-B stages free from crossover artifacts are so far beyond us."
THat sums it up. He found a way to mostly eliminate all the distortions on his list EXCEPT distortion 3, which are inherent traits of transistors when running Class B.
Doug Self, himself, has declared that avoiding zero crossing distortion in Class B transistor amps is IMPOSSIBLE with current semiconductor technology.