Gibson amp dating
This month we’ll look at four basic versions of the EH-150, which showcase a number of the technological improvements that transpired from the mid ’30s to the start of WWII.These will be referred to here as Styles 1 and 2, having the smaller “square-corner” box with 10″ speakers and Styles 3 and 4 with the “rounded-corner” box housing 12″ speakers (there were actually two slightly different sizes of each box).More important than that grand revelation would have to be the inclusion of an extension speaker output and matching speaker/cabinet setup, which today may also not seem like such an earth-shattering event.However, the intended application of the 1/4″ jack was described in an early owners manual as follows: “Its use presents many new possibilities.Access to the interior is a breeze, with the chassis secured to the cabinet by a single large bolt from underneath protruding through the metal topside before being capped by a fancy brass nut.Alligator cloth/paper lined the insides of the tweed-covered cabinet as neatly as plaid would line a suitcase of the era, a very pleasing touch.This triode (actually twin triodes in parallel for Class A operation, as specified in the RCA tube manual) was fed directly by the parallel inputs and was all she wrote in the preamp tube gain department (amplification factor of approximately 35, compared to 100 for the modern 12AX7).The paralleled plates in turn directly fed the phase inverter, with no need for coupling caps.
Whoever was building these – and it wasn’t the Gibson factory – knew proper assembly techniques (and could have taught Leo Fender a thing or two in his early days).
The first production wood-bodied Hawaiians of early ’36 also came with this simple circuit, but by the end of the year Gibson had an improved model it could call its own.
And for the next 30-plus years, they would stay at the forefront of guitar amplifier design, a fact often overshadowed by Fender’s dominance in the vintage market.
Rey had long been associated with the pre-Rickenbacher brand Electro Frying Pan and amps, which reportedly were role models for the experiments.
While Gibson’s first real test run of aluminum-bodied Hawaiian models in late ’35 arguably showed little influence of the Chicago pickup experiments, the four-tube amps that accompanied the instruments had a definite leaning toward Alvino’s personal Electro amp.
The power cable, fuse holder (round, house-fuse style on earliest models), on/off switch, pilot light, and two inputs were all secured directly to the backside of the bottom-mounted, bent-metal chassis.