The same handful of design decisions recur across four decades of amplifiers — how the signal is split for a push-pull output stage, how the output tubes are biased, what rectifies the high-voltage rail, and how the tone controls are wired. Each choice below gathers every amp in the corpus that made it, side by side with the neighbouring circuits that chose differently.
How a push-pull amp splits one signal into the two opposite-phase drives its output tubes need — or why a single-ended amp needs none.
How the output tubes are held at their idle operating point — a self-setting cathode resistor, or a separate negative supply.
What turns the power transformer's high-voltage AC into the DC B+ rail — a vacuum diode that sags under load, or stiff silicon.
The passive control network that shapes the amp's response — from no tone control at all to the three-knob stack that defined lead tone.