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Vintage Gibson Amplifiers

EH-100 and 125
 
EH-100 and 125

“No longer is the electric Hawaiian Guitar restricted to professional players – here is a genuine Gibson instrument that costs only $100, complete with instrument, case, amplifier with slip cover, and cord.”

So introduced in Gibson’s Catalog X of very late 1936, the EH-100 Hawaiian set cost a third less than the company’s EH-150 set, which by this point had the updated six-tube chassis and “Echo” extension speaker.

While National-Dobro had already released its lower-priced Supro line and mail-order catalogs like Montgomery Ward, Speigel, etc. offered early electric sets for under $100, they didn’t say Gibson. Like the competition, the earliest EH-100 guitar lacked the Alvino Rey-designed tone control, but it wasn’t long before Gibson added one to its lower-priced instrument, making the 100 set comparable in performance to the four-tube 150 sets from earlier in the year. Like these early 150 amps, the four-tube 100 amp lacked both volume and tone controls.

It should be noted Gibson did not offer a Spanish-neck electric guitar to go with the original 100 amp, as they were just releasing their first magnetic-pickup electric Spanish, the ES-150 (which wouldn’t be shipped to dealers until ’37). Despite their relatively late start, the company would quickly go on to dominate the pre-WWII electric market, with a full line of high-end instruments, such as mandolins, banjos, doubleneck Hawaiians, an early pedal steel, experimental violins and basses, etc.

Complementing these at the lower end of the market were the small line of 100 (and later 125) instruments and their matching amplifiers. Covered here on a year-to-year basis, it’s evident Gibson not only changed the EH-100 amplifier’s look annually (think automobile manufacturing), but the engineering department was continually upgrading the circuitry.

1936-’37 (Catalog X)
Offered on its own at $50, the first EH-100 amps were promoted as the mate to the new EH-100 Hawaiian guitars. Dressed in “Strong imitation black leather covering” with a white Gibson logo stenciled on the lower right corner of the face, the box housed a 10″ field-coil speaker and a bottom-mounted, rear-facing chassis. Embossed lines framed the perimeter of the cabinet, with metal corner protectors on the bottom.

Like the early E-150 model, only two stages of amplification were employed, with a 6N7 twin-triode (amplification factor 35) handling the gain department (again, run in parallel for Class A operation, as specified by the RCA tube manual). Twin 42 power pentodes operating in push/pull were probably fed by a transformer phase inverter, although there are other, less-than-ideal (but cheaper) ways to achieve this function. It’s doubtful whoever was designing Gibson’s amps at the time would have chosen such a circuit for a high-fidelity amplifier (anybody have one of these black-covered models?).

Also like the first E-150 amps, the first 100s got their juice from an 80 rectifier, came fitted with two parallel inputs and had no controls in the circuit. A fuse was the only other “feature” of this bare-bones model. It’s interesting there was no tone control on the first EH-100 guitars either, though this would soon change as the last of the black-finished 100 Hawaiians had the modern two-knob arrangement.

1937-’38 (Catalog Y)
By the release of the next catalog (which were being cranked out annually during this progressive era), Gibson offered both a new look and a new circuit for the now $110 EH-100 set ($55 for the amp alone). The new model amp was covered in “Very handsome tan aeroplane cloth covering – this material is tough and can be washed.” Dark stripes running vertically accented the light colored covering, as did the logo, the bottom-mounted leather corner protectors and the big brown leather handle, as seen on the EH-150 amp.

A three-stage circuit using five tubes was instituted, with the original 6N7 replaced by a 6C8 twin-triode (amplification factor 36) and a single-triode 6C5 (amplification factor 20). Again, two inputs were standard, but only one was for the instrument, with the second specified for use with a microphone. While not mentioned in the catalog, this version’s schematic shows a volume control operating on the mic input only (the AC power switch was shown built into the volume pot – turning the volume knob turned the amp on). Each channel used its own section of the 6C8 preamp tube.

Under “Tubes” in the “Electric Guitar Supplies” section of the catalog, the relatively new 6V6 beam power tubes were listed, implying a change in the output section occurred after the schematic was drawn up, but prior to the catalog’s release. This also suggests that either the first tweed 100s still used the 42 power tubes, or there were later version black-covered amps with the new five-tube circuit.

1938-’39 (Catalog Z)
A new look for ’38 featured “handsome dark brown Aeroplane cloth with harmonizing yellow stripes,” and a matching logo. The pattern of the stripes was the same as previously used, only rotated 90 degrees, to the horizontal plane. Dimensions were given for the cabinet as 12″ high, 14″ tall and 7″ deep. An enclosed back was added, as seen on the 150s, and the leather corner protectors were replaced with metal, although these were not included in the catalog shot.

“Has six tubes and three stages of amplification with 8-watt output.” Unfortunately, the tubes were not listed (and somebody here didn’t do enough research!). Gibson made no mention of “seven (or eight) tube performance,” so it’s hard to speculate whether they used any twin triodes in the new circuit. An extra gain stage for the mic channel seems a safe bet, but as to whether a transformer was still being used for the phase inverter, as on the seven tube 150, or the function was performed by a tube, as on the ’40 EH-100, we’ll have to check and report back later.

By ’38, it was obvious to Gibson that electric Spanish guitars were a viable offering and they expanded that portion of the line to include the new ES-100. Like the EH-100 Hawaiian, the Electric Spanish model was “designed for use with the EH-100 amplifier” (the first of these guitars may have come with the earlier five-tube 100).

1939-’40 (Catalog AA)
Cosmetically, the ’39 model appears similar to the ’38, except for the number and spacing of the “harmonizing” stripes. Again, the text also specified metal corners, although these were not included in the updated, retouched picture. The description of the electronics was unchanged.

Gibson provided their services to numerous wholesalers for “contract brand” instruments, e.g., Cromwell (C.M.I.) and Capital (Jenkins), who offered 100-style amps with the enclosed case. These are not to be confused with Gibson’s in-house bargain line, Kalamazoo. By the late ’30s, Gibson’s budget line had been expanded to include electrics, which allowed the company to put a better quality 100 line out and still offer a competitive line under it, as the cost of building amplifiers dropped in the second half of the decade.

1940-’41 (10/1/40 supplement)
Introduced around the same time as Gibson’s short-lived top of the line EH-275 amp (in natural maple – info/photos, please!!), the dark grained $60.50 EH-100 amp would, like the 275, not survive to the next catalog installment. National was already in the middle of a massive advertising campaign for its wooden-cabinet Model 100 Deluxe, Epiphone had released its ever-so-stylish curly maple models, and Vega was joining in with its redesigned two-tone woodies. So Gibson was merely keeping up with the fashions of the day.

A 12″ X 15″ X 8″ rectangular cabinet constructed of 3/8″ solid mahogany was Gibson’s mate for its new (and equally short-lived) unbound, slab-bodied EH-100 Hawaiian guitar; “Natural finish mahogany instrument and amplifier both perfectly matched in quality and appearance.”

The removable open-back lid housed a 10″ speaker, with the chassis also encased in mahogany; “Amplifier chassis and speaker in one case for ease in carrying, but may be detached to eliminate tube rattle and other noises.” There appears to be an inherent structural frailty to this design, compared to the enclosed cabinets that preceded and followed it. However, this is without a doubt the looker of the bunch! The example shown here, courtesy of Ray Pirotta, is reported to be a real screamer, too.

Tubes included a 5Y3 rectifier, twin 6V6s for outputs, a 6N7 twin-triode phase inverter, a 6C5 triode preamp common to the Microphone and Instrument channels, and a 6SQ7 triode (amplification factor 100) for additional microphone gain. As on earlier models, the volume control worked on the mic input only. What is now referred to as a “Fender-style” leather handle replaced the large variety that would continue to be used on the 150s.

EH-125 1941-’42 (May 20, 1941 Supplement and Catalog BB)
Gibson quickly reverted to its enclosed-back design for the wooden 100’s replacement, the newly named (and improved) EH-125, costing $125 for the Hawaiian set or $65 for the amp alone. The round-shouldered cabinet appears similar to the one used for the 150 amps, save for the “…rich cordoba brown covering.” The large handle was also reinstated and a 12″ speaker replaced the long running 10″, making the 125 more of an inexpensive 150 than an expensive 100.

Electronically, the 125 was based on the twin-6V6-powered 100 it replaced, albeit with a revised circuit. The 6SQ7 mic preamp and 5Y3 rectifier remained, but the 6C5 triode common to both Microphone and Instrument inputs was replaced with another high-gain 6SQ7. A 6J5 single triod replaced the previous 6N7 for the phase inverter function, with Gibson claiming four stages of amplification. Also like the 100, the 12 included three inputs, with the Volume control effecting the mic input only.

EH-110 1937-’42
As mentioned in last month’s EH-150 article, Gibson offered special-order universal AC/DC amps based on their regular line. Unfortunately, there is even less info on the 100’s offshoots than the 150’s. Catalog X made no specific references to a 100 variant, saying, “Write for information about Amplifiers made for AC/DC Current” at the bottom of the EH-150 page.

Catalog Y made a specific reference; “EH-110 Model – Same as EH-100 model but with special unit to be used on either AC or DC current.” All Gibson amps were available as Universal models until electric products were discontinued during WWII, with a $10 premium added to the regular prices. Besides the AC/DC models, Gibson also offered a six-volt DC battery-powered version of both the late-model 100s and the 125s. Since automobiles were equipped with six-volt DC electrical systems, it seems obvious what these amps were designed for.

Postscript
Due to the constant changes in models, none of the 100 amps were around long enough to be made in great quantities. Therefore, it seems safe to say all 100s and the 125 are now medium-rare to rare models. Although not generally associated with the big names and comparatively underpowered, the 100 amps (and their associated instruments) stand up favorably to Gibson’s higher line models, as well as the competition of the time.

Thanks to Experience Music Project for the catalog shots, Ray Pirotta for the ca. ’40 EH-100 amp, and Lynn Wheelwright for the matching Hawaiian guitar.



1940 EH-100 set in solid mahogany. Amp courtesy Ray Pirotta, guitar courtesy Lynn Wheelwright. Photo: Bob Fagan.

This article originally appeared in VG‘s Aug. ’99 issue. All copyrights are by the author and Vintage Guitar magazine. Unauthorized replication or use is strictly prohibited.

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