The "Four Ten" almost needs no
introduction - based on one of the greatest
and most famous guitar amps of all time -
the "5F6A Bassman".
40 Watts into four 10" speakers with bass,
middle, treble and presence controls, the
5F6A was the final evolution of the "tweed"
series of amps.
When Jim Marshall wanted to introduce his
first guitar amplifier he made an almost
exact copy of the 5F6A and the DNA of this
circuit lives on in many new tube amps
The "Four Ten" has a fortuitous combination
of low gain 12AY7 preamp, more "modern"
"long tailed pair" phase inverter and still
too wimpy power supply providing plenty of
For comparison the Marshall amps evolved
from this circuit with a beefier power supply
(for less sag) and a higher gain preamp -
you can get closer to this sound by
swapping the 12AY7 for a 12AX7 whenever