Just a few things if I may...... A "CB" style "class C" amplifier *COULD* sound ok on AM and SSB although this is not proper, and I would never recommend it. The reasoning behind this is because these amplifiers, while by definition ARE IN FACT class c, they are not biased deep into the class c region.
Meaning, in order to be completely deep into the class C region, they would have to have a negative bias supply pushing them deep into class C which would, just like a proper bias supply pushing the transistors towards B, or AB, cost the manufacturer money and time. Then you would have a true class C amplifier suitable for FM and CW only. And even them, some bipolar transistors do not like this deep "switching" mode and it can cause "hot spotting" and other phenomenon.
Ok back to it... so instead in most CB amplifiers the base (input) of the transistor is often just tied to CBG (circuit board ground) at 0 volts potential putting the transistors right at the border of class "C" and "B". True class "B" would call for forward bias, so we call them class C. Remember for class "C" conduction angle needs to be 90 degrees and for class "B" it is 180. What I usually see is something in between.
So..with a little forward bias, things go more into the B region, and then add a little more Ic (bias, idle current, etc) and we get more than 180 but less than 360 which is "AB" and fine for most operation as long as the bias source is a low impedance source and does not fluctuate all over the place, has proper RF bypassing and does not go negative on voice peaks which in some CB amps is typical.
On another note, I see a lot of people refer to their solid state, transistor amps as AB-1, AB-2, etc. This is IMPOSSIBLE. The reason for this, is AB-1, and AB-2 refers to a TUBE amplifier with the "1" or the "2" referring to which element in the tube is biased toward or against another element. This is NOT SO obviously with a bipolar transistor.
So bi-linear is misleading as well. It would tell you that is is a linear amplifier with a receive amplifier. I have even seen some CB amplifiers stamp AB-1 on the front. They obviously mislead and have no ideas themselves what they are building I guess.
To answer the question on the TX-75, it would be by definition a class C amp, but as referred to as earlier not deep into class C. But not "linear" either.
One last comment about class c. There is a push pull design phenomenon that does occur when two devices are put in stages once again common with CB amplifiers. It tends to replace the missing half of the cycle or part of it depending upon the design. To explain it all would be outside the scope of this post, but if anyone is interested I could do a write up on it.
This is all very old concepts, and technology. I suggest reading some older material such as ARRL handhooks from about 1945-1960 for information on AM, so called "NPC" that we see on here attempted a lot where modulated positive peaks exceed 100% and negative are limited to reduce interference and distortion. They also go into great detail about using class C for modulated modes, and the difference between feeding modulated RF through the amp and modulating the stage directly.
