Gibson’s E-150/EH-150 amplifiers have long been regarded as the quintessential pre-WWII model, one of the most influential and recognisable amps of all time. It wasn’t the first amp Gibson marketed for use with an electric guitar and it wasn’t originally designed or even manufactured by Gibson. But it will forever be associated with the early days of Gibson’s long-running stellar electric line.
Electric guitar pioneer and Gibson endorser Alvino Rey worked on the company’s behalf in Chicago in mid 1935, along with engineer John Kutilek of Lyon & Healy, trying to develop an electric Hawaiian guitar and amp set worthy of the Gibson name. 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 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. If nothing else, the beautiful tweed cabinets of the pre-WWII Gibsons set a new standard for design – no more plain black boxes!
But more important than cosmetics, the late-’36 Gibson EH-150 stands out as the first amp to pursue the idea of tone manipulation as opposed to merely amplifying what the guitars sent their way. Rey is credited with designing the high-frequency roll-off tone control for guitars, which Gibson introduced to the world on the aluminum Hawaiians. The general idea was incorporated into the amp as a tone switch, to be used in conjunction with the tone pot on the guitars.
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. The true Echo effect is obtained by placing the E-150 speaker and amplifier near the player and the Echo Speaker at an approximate 35-foot distance, preferably further from the audience and to either side. The slight sound-wave lag time…creates a new and beautiful effect.”
A second, more practical (for the time, at least) example followed.
“When using a vocal microphone the additional loudspeaker is also desirable, permitting better and more complete coverage of the audience.”
But while this use had been explored in PA system design for years, the “…beautiful effect” preceded all other “effects.” The idea of intentionally altering the acoustic sound of a guitar – embellishing it – and pursuing a more pleasurable sound cannot be ignored in historical contexts, for the future of Spanish guitar had little room for dry, flat tone. Remember, electric Hawaiian guitars, which inherently produced vibrato-drenched tone, outsold electric Spanish models by as much as 10 to 1 in the pre-effects days.
The first version of the E-150 amp (1935-’36), had like all amps of the time, no control panel on the chassis. 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. A black crinkle paint covered all the exposed surfaces and, like many of the amps of the time, there were no volume or tone controls.
Four tubes were laid out similar to Alvino’s Rickenbacher, to the left between the power transformer and the speaker came either a glass 80 or metal 5Z4 rectifier. Twin 6F6s for the power were mounted catty-corner to the right of the speaker with a shielded 6A6 preamp in the front right corner. 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.
Like many amps of the era, phase inversion for the push/pull outputs was performed by a transformer of the center-tapped secondary type, which stepped up the voltage negligibly while providing equal but opposite signal to the power tubes.
This device was mounted to the back wall of the chassis (opposite the inputs), as were the power supply filter caps (two large boxes). Between the front and back panels were the tube sockets, with only a few resistors and caps professionally connected using binding posts, a large grounding strip, and neatly tied wires. 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).
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. A small label attached to the inside surface of the removable back cover (also lined) had the serial number pencilled in. This number also shows up inside the chassis and on the magnet cover of the speaker. Utah’s respected 10″ field coil model, previously used by Rickenbacher, was standard.