Tech Talk - Gibson GA-90 (1956)

A "Revelation in Rythm" - the GA-90 was introduced alongside Gibson's first electric bass - the violin-shaped EB-1. Finished in dark brown "buffalo-grained" leatherette.

The amplifier features six 8 inch speakers, strangely enough it may seem. The confined throw of a speaker from that period combined with a small cone area makes it less appropriate for deep bass reproduction. Just adding more speakers won't do the job. This amp was designed by Seth Lover to rid the problem of the large single coil pick-up for the new bass guitar

that "would make a god-awful hum" when it got to close to the amplifier. Later he would try solving this problem by designing the "humbucking" pickup. Top mounted preamp with control panel and a bottom mounted chassis for the main amp. 25 watts output.
Speakers 6-8"
Inputs
(instr. + mic.) 2+2*
*hi-gain sw. 2
Channels 2
Volume Controls 2

Bass, treble
for ea. ch. No
Tubes 8
Preamp. 2-6SJ7 2-5879,
Phase splitter 6 6SL7
Output (5881)
Rect. 5V4 5Y3
Watts Output 25

Tech Talk - Gibson GA-40 (1957)

Surprisingly, the GA-40 wasn’t Gibson’s most powerful amp of the time, contrary to the kind of firepower that you might think the powerful Les Paul Standard demanded. But remember, the Les Paul wasn’t designed to be the blues-rock and heavy-rock monster that it would prove itself to be in the mid ’60s and beyond. It was originally designed as a solidbody alternative for jazz and pop players, guitarists much like its namesake, and for this market, Gibson deemed a pair of lower-powered 6V6 output tubes and a conservative 14 to 16-watt rating absolutely adequate. Don’t believe for one second, however, that this diminutive rating means a GA-40 can’t roar when you want it to: these are real fire breathers, truly scorching when you crank them up, and a lot louder, too, than that output rating might imply.
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Tech Talk - Gibson GA-20 (1956)

Gibson GA20 (1955)
Speaker Config: Jensen P12R
Wattage: 12w
Tube Setup: 5Y3, 2x6V6, 12AY7s

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Tech Talk - Gibson GA-6 (1954)

GA-6 (tweed)

10-14W 2x12" Guitar Combo (identical to the GA-14 Titan except for the 12" speaker)
Speakers: 2x12"
Inputs (instr. + mic.): 2+2 (tweed)
Channels: 2
Volume Controls: 2
Tone Controls: 1
Tremolo: No
Tubes: 5 (2x12AX7, 2x6V6, 5Y3 or (newer version) Pre (2x7025), Pow (1x6V6 PAIR + 5Y3))
Watts Output: 10-14
Shipping Totals: See GA-6 (two-tone)
Harmony Central Review GA-6
Schematic with 2x12AX7, 2x6V6, 1x5Y3

For info on and pics of the Gibson GA-6 Interim Model see Miles O'Neal's web-site.

This amp replaced the BR-6. The circuit is identical to that of the GA-14. (www.drtube.com, March 28, 2003)

Push-pull 6V6s; like a Fender 5D3/5E3 Tweed Deluxe; cross between the two Fender circuits

Tech Talk - Gibson GA-30 (1948)

Here's our daily amp video. These old Gibson amps can really have an interesting sound. Designed to be played with a humbucking pickup they are totally different from a fender based design.

Gibson GA-30(1948)
15Watts 1x8" & 1x12" speaker

Built some two years after Django's 1946/7 American Tour this amp is barely comparable to that which was used by Django to be heard adequately while the Duke Ellington Orchestra wailing alongside him. His must have been a special and who knows perhaps a prototype issued by Gibson to support their Gibson ES300 Guitar used by Reinhart throughout the tour. He wasn't well received by the Ellington Fans who were more than discontent if the band remained silent but for a few riffs and a crescendo during his sets. Django was lone figure without his usual support and Ellington had not written anything special for his unique talents, but there again Django new nothing of Key's or reading Music Notation, didn't speak much English and always played by ear. What an educated ear and a matchless improvisational talent!

Note the 'very large for the times' white Amp to the left of Django with Gibson and that closed striped case at his immediate 'left' which also appears on the La Plar Ballroom Picture with a small black amp connection box stood on edge to the camera.

Anyone have any ideas on this Amplification arrangement - early 'Vibrator' type power unit or pre-amp perhaps. Was it a Seth Lover Special as it closely resembled the much later Fender Amps in size suggesting multiple speakers.

Could the case be the controls and the large White Box just the speaker housing?

The GA 30 must have been about 24 x 18 inches say 610 x 460mm

The GA-30 with a picture frame style speaker opening and dark brown leatherette covering. "New bass tone expander control allows the player to increase resonance and quality of the lower notes, advantageous in instrumental solo work".

First version of the series with 1-12" & 1-8" speaker. Massive magnets made this a very heavy amp.

Has a GREAT low volume Jazz tone that is the Charlie Christian tone all over again with the right guitar.

Tech Talk - Vintage Amp Gibson GA8

Another coll small amp for guitar or harp:

GA-8 Discoverer (Crestline)

15W 1x12" Guitar (Harp?) Combo
Speakers: 12" (Jensen)
Inputs: 2
Channels: 1
Volume Controls: 1
Tone Controls on Each Channel: Bass, treble
Tremolo: No
Reverb: No
Tubes: 5 (6EU7, 6C4, 2x6BQ5, 6CA4 (correspond to Epiphone EA-35 Devon))
Diodes: 0
Extension Speaker Jack: Yes
Monitor Jack: Yes
Watts Output: 15
Shipping Totals: 1962: 841, 1963: 188