THD BIVALVE-30 INSTRUCTION MANUAL
3
TABLE OF CONTENTS
Instruction Manual .................................................................................................. 1
What Does “Class-A” Mean? ....................................................................................... 3
BiValve-30 Controls...................................................................................................... 4
Front Panel.................................................................................................................. 4
Back Panel .................................................................................................................. 6
Switching Tubes in the BiValve-30............................................................................... 7
Power Tubes ............................................................................................................... 7
Preamp Tubes ............................................................................................................. 7
THD Electronics Contact Information......................................................................... 8
What Does “Class-A” Mean?
At the beginning of this manual, we explained that the BiValve-30 is a “Single-Ended
Class-A” amplifier—but what does that mean? “Class-A” is a term given to an amp that
runs its tubes at full current all the time, unlike most tube amps that alternate between
running one set of tubes and the other set, each for one half of the wave. The set not in
use is turned off by a positive swing of the grid voltage. Single-ended out-put stages
always operate in Class-A. Most guitar amplifiers over 5 watts operate in Class-AB
Push-Pull. The upshot is that Class-A operation has its own unique tone characteristics
that set it apart from other tube amp classes. Class-A amps sound great at low volumes,
and even better as you turn them up. There is no point at which you will be waiting for
the tube to receive its full current for the best sound—it always will.