First of all, why the hell is there only ONE pre-amp tube used IN EVERY FUCKING TUBE AMP?

If you actually took the time to learn about valve theory and history, you would know. But feel free to rant that there most somehow, somewhere, be something better or different out of an ignorant rant.

Despite all the different shapes, sizes, pinouts, and names, just about every preamp tube comes down to either 1) audio stage pentode 2) audio stage triode, or 3) driver stage triode. The voice of the amp comes from how you use those stages, not what shape the tube was. The evolution of the miniature noval tubes was a massive jump forward in reliability, efficiency, flexibility, and other all appliance size. It dominated both the military and household appliances. By the time the next generations appeared, it was the early '60s and tubes were obsolete in homes and the military wanted to stay backward compatible. The reason Gibson and Ampeg switch to more obscure tubes in the '60s is because they bought out all the liquidated stock of 6EU7 and compactron tubes. So, for 70 years, the 12AX7 has been the dominate dual triode audio stage, and the 12AT7 and 12AU7 has been the dominant dual triode driver stage (despite your believe they only vary on gain, the tubes are actually built entirely different for very different jobs)...the idea of a pentode preamp tube were abandoned as noisy and microphonic, which is why the EF86, 5879, etc. where almost never used after 1962.