The First Ever Class A Tube Amplifier With an Overdrive Channel.

1937 Gibson EH 150 Round-Shouldered Cabinet.

This all original 15 watt tweed cabinet tube combo legend weighs 29.00 lbs. The solid pine cabinet measures 16 /1/2 inches wide x 15 1/2 inches high x 9 inches deep. The back of the cabinet (with matching serial number written in pencil) is attached to the main body by four latches. One original ten-inch Gibson 'High Fidelity Ultrasonic Reproducer' speaker with stamped codes "12F40" and "A020". Rear control panel with two instrument inputs, and one microphone input. Two separate volume controls (Instrument and Microphone), one two-way tone switch and an external speaker output. Original 'tweed' tan cloth with vertical stripes covering with circular aluminium mesh speaker cover. The serial number "13058" and the Model "EH150" are stamped onto a plate attached to the chassis. The electrics are 100% original and untouched other than changed (3 x 6C5; 1 x 6F5; 1 x 5U4G & 2 x 6L6GC) tubes. The 'tweed' covering is in very good condition, the original leather handle has some wear but is still functionable. An incredible seventy-seven-year old legend… just turn it up for real tube gain at a reasonable volume.

The first Gibson Electric Steel Guitar was produced around 1935, which was one of the first production amps made. This guitar came with a matching amplifier, the EH-150 (a model EH-100 was also available). These first amplifiers were manufactured by Lyon and Healy. Many times the guitar was sold with the matching amplifier. These amplifiers were produced up until the start of World War ll. After the war a new line of amplifiers emerged. The EH-100, EH-125, and the EH-150 are the three more known amplifiers in the EH series.

This is one of the first guitar amplifiers produced by Gibson for the commercial market.  The model shown is the EH-150, made sometime in 1936 or 1937. 
It featured a 10 inch electrodynamic speaker driven by a pair of 6N6 direct coupled triodes, with a potential for about 15 watts output.  Three 6C5's and one 6F5 provide the low level amplification.  Interestingly, in the unit shown here, the clearance between the output tubes and the speaker is very small (the speaker is original), making it impossible to use the glass version of the 6N6 (the 6N6G).  The tubes shown here are the earlier (and rarer) metal-glass versions (the 6N6-MG).  Other pictures of this amplifier that I have seen show the 6N6G's, so it is possible that Gibson changed the speaker design to allow use of the later tubes.
150 guitar (similar to the one from Christian's early Goodman days) to keep at the club for his use (more on this later). Check out Charlie Christian - Live Sessions At Minton's Playhouse on the Jazz Anthology label to hear why his playing and the sound of the ES-150 through an EH-150 amp continue to thrill and inspire listeners and players the world over, as they have since 1939. And while his playing surely could have transcended his equipment, the fact he used an EH-150 for a good portion of his career guarantees the model a place in the Vintage Guitar Amplifier Hall Of Fame.Speaker size increased to a 12" field-coil with the Gibson name on the magnet cover.
A beefed up circuit employing seven tubes featured the relatively new 6L6 beam-power variety, in metal. The 5Z3 rectifier, 6C5 driver and 6F5 microphone channel primp remained from the earlier model, but the twin triode 6N7 was replaced with two 6C5 triodes for the instrument and microphone channels. Power ratings were given for the first time, a respectable 15 watts.
It appears this version ran for a number of years, as the picture and basic description from the late-'37 Catalog Y also showed up in catalogs Z from late '38 and AA from late '39, plus AA supplements dated October 1, 1940, and May 20, 1941 (shown with the slant pickup on the instrument replacing the Charlie Christian-type of the earlier catalogs). These "What's New" flyers from '40 and '41 replaced the AA electric section, due to rapid changes in that segment of the line. The first supplement showed new or updated artist renderings for the EH-185, 150, and 100 Hawaiians, the EH-100 amp and the ES-150 and 100 Spanish Guitars. Number two had the second-style ES-300, the new EH-125 Hawaiian/amp set and up-to-date prices, so they appear accurate, although they did not show the change from brown alligator lining to light cream leatherette on the 150. Finally, Catalog BB included the last version of the 150 amp, referred to here as Style 4.
Some examples from this era have two labels inside the cabinets – one for Geib, who made guitar and amp cases for Gibson, and a Western Electric licensing agreement granted to Electrical Research Products, Inc., who also made amps for Oahu, Harmony, etc.
Gibson EH150 Amplifier was also used by Django and having looked at the interior wiring shots its a marvel that our man was not electrocuted mid solo flight. 

The EH-150 amp cabinet was covered in "Aeroplane cloth", luggage tweed, with contrasting vertical brown stripes. A black perforated aluminium grille protects the ten inch "Ultrasonic High Fidelity Reproducer" speaker. Later Gibson would often affix red stickers onto the back of speakers with the printed text "Ultrasonic Speaker". Especially during the '60s and '70s. Chassis were mounted at the bottom of cabinets. The features of the early EH-150 amp include one input for microphone and three inputs for instruments, separate volume controls for the microphone and instruments sections, a bass-tone expander switch, and an "Echo" extension speaker jack. 

For the microphone input stage of the early EH-150 one 6F5 tube (high mu triode) was used and one half of an 6N7 (dual high mu triode) to provide gain for the instruments input and the second half to a second gain stage for both input stages, one 6C5 tube (medium mu triode) to serve as a third gain stage and a transformer to split the phase of the amplified signal into two 6N6 output tubes (direct-coupled power triodes. 
One 5Z3 rectifier tube was also used. 

The '37 EH-150 was the first ever class A tube amp with an overdrive channel. It is claimed it still sounds better than just about anything out there. It has one knob---volume More Pic's 

Amplifiers of the day were just as basic as the early electric guitars, if not more so. The EH-150 had in fact arrived before the ES-150 guitar, as partner to Gibson’s EH-150 lap-steel guitar (these were actually Gibson’s first genuine electric guitars, and the amplifier retained the lap steel’s “Electric Hawaiian” designation). The EH-150 originally carried a single 10" speaker (later a single 12") and was powered by a truly archaic circuit design, and now-obsolete preamp and power tubes, but it was an impressive beast for the mid ’30s. Even when the circuit had evolved a few years later to employ 6L6 output tubes, the amp still only produced around 15 watts at best, but that 15 watts sounded pretty darn loud next to any acoustic-only rhythm guitarist hacking away in the rhythm section, so these amps were enough to unleash the guitarist as soloist on the big-band stages of the day. 

Charlie Christian to Gibson ES-150 guitar to Gibson EH-150 amplifier … to history. It’s a humble rig by the current standards but today’s electric guitarists have it to thank for proving what this instrument, and a great player, could do.