Vintage Guitar - July 2018 - open - 93
'52 Bassman: Ron O'Keefe.
A look at the
installed) dual-ported rear enclosure. Its wiring (left) is rudimentary,
and the control panel hosts dual inputs, Volume, and Tone controls.
mounted on an upper panel connected by
what collectors call the "umbilical cord"
running from a socket to the lower chassis
that housed the bulk of the electronics.
The back was enclosed by a panel with two
round ports - a clear intention to entice a
fuller, more bass-heavy response from its
A schematic exists for what is believed to
be a first-iteration Bassman (circuit 5A6),
but no examples of the amp have surfaced
in this format. The diagram shows a circuit
with two octal 6SJ7 tubes in the preamp,
a 6N7 phase inverter, two inputs for one
channel and one for the other, individual
channel Volume knobs, a shared Tone
' 52 B A SSM AN
control, and two output transformers
feeding the two speakers. This is the
exact configuration of the V-front Dual
Professional from 1947, which seems to
indicate someone doctored and re-labeled
the schematic for that amp.
In '53, the Bassman migrated to Fender's
new "wide-panel" tweed cabinet but retained its split-chassis construction even
though it was the same physical size as the
Pro and new Bandmaster (both of which
were 1x15" configurations). And while it
seems odd that the Bassman didn't share
its siblings' upper-mounted chassis, it did
retain the ported back panel, which was good
since there likely would have been heat issues from upper-mounted tubes suspended
so close to that piece of plywood. As it was,
though, heat from the bottom-mounted
chassis was able to rise and partially vent
through the ports.
In any case, this short-lived back panel was
seen as important enough to low-frequency
reproduction as to warrant the odd constructional format. During the wide-panel
years, the Bassman also transitioned from
octal preamp tubes to more compact
nine-pin tubes, using a 12AY7 in