What is B+ power?

B+ and B- were the high-tension (HT) supply used in thermionic valve radio equipment.

A+ and A- were the filament (heater) supply C+ and C- were the grid bias

The B is from the 2 humps of the half wave rectifier.B+ uses the two positive cycles of the AC signal in a half wave rectifier. B- powersupply uses the 2 negative pulses of a half wave rectifier. A full wave rectifier flips the 2 negative going ac pulses to the + side using the full power of the AC signal for DC. A half wave uses only half the power.

}A+ and A- were the filament (heater) supply }C+ and C- were the grid bias } Andrew Holme

Sometimes called the "Plate supply".

Except that the designations were originally for battery-powered equipment, with A, B, and C batteries, as others have noted.

Besides, if we were dealing with voltage bumps, the positive would be the M supply, and negative would be W.

John

Nonsense. As was already correctly said elsewhere, the "B" designation dates back to the early days of battery-operated tube (valve) radios, in which the "B" battery was the plate (anode) supply. The "A" and "C" designations have long since died out, but for some reason you still will come across the "B+" designation used in many schematics, even those of fairly recent vintage.

Bob M.

The B battery supplied the high voltage for tubes in the early days. There really was a B battery, as there was an A battery for the filament.

So "B+" became the label for the high voltage bus in equipment. It became so standard, that the term remained even when voltages got a lot less with solid-state equipment.

Michael

Or the "anode supply voltage" in Britain. Typically several hundred volts upwards.

Sure, but not on a schematic as the letter identifying a power supply.

Bob M.

Right, the 'B' battery was typically 90v. The 'A' battery (1.5V) supplied the filaments and the 'C' the grid bias.

You've never seen a 'C' battery?

That's only because the few places there are grids, they're biased other ways. The 'C' battery remains, however. The 'A' has gone pretty much the way of the DoDo, though.