Why is the bias supply capacitor backwards (plus to ground instead of negative)?
Normally in a tube amp, you are dealing with a positive voltage (B+) with reference to ground. But with a bias supply, you are dealing with a negative (C-) reference to ground. Ground is just a handy reference when it comes to voltages – remember that you can have AC ground, signal ground, and PS ground – and they’re all usually the same ground! -Miles • Why is the high voltage called B+? What are A, B and C voltages? These letters once refered to battery classes for circuits. (You’ll notice that tube texts generally show batteries as power sources for the various DC voltages – they meant it!) A batteries were for the heaters (filaments). B batteries were for plates and other (relatively) high voltage supplies such as screen grids. C batteries were for control grid bias supplies. The B voltage is positive (B+). The C voltage is generally negative (C-). The A voltage polarity generally doesn’t matter, but if it’s DC should most likely be positive. Today, B+ is about the only one of thes
