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introduces ghost tones by progressively reducing capacitance in the power supply, and that
it is these same filter capacitors that take in the bumpy DC signal from the rectifier and
put out a smooth voltage for the power amp to use. You can think of the GHOST control as
effectively changing the size of these capacitors, making them smaller as you turn
clockwise.
With the GHOST knob fully clockwise, the capacitors run out of current very quickly and
sag occurs almost immediately. Conversely, with the GHOST knob fully counter-clockwise,
the capacitors are larger and can go on delivering full power for a bit longer, delaying the
onset of sag. In this way, turning the GHOST control counter-clockwise is like
progressively going from a particularly old vintage amp with technically inferior capacitors
to a modern amp boasting better quality components that offer a larger charge capacity.
Remember that, regardless of which rectifier you use or where you set the GHOST control,
the amount of sag you experience will always depend on how hard you are working the
power stage. Sag occurs when the power amp is asking for more current than the power
supply can, at that moment, deliver. The amount of sag, and its onset and recovery
characteristics, will therefore depend on the level of your input signal, how hard you play
and how high the VOLUME knob is set.
If you want a visual clue to sag behaviour in the RevivalDRIVE, watch the channel
indicator LEDs and main jewel light. As with many vintage amps, these lights are fed by
the main power supply and will dim as it sags. By watching them as you play, you can
train your ears to identify different sag characteristics and decide which you prefer.
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