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The Gibson Skylark  GA-5 and GA-5T
The Gibson GA-5 began life as the Les Paul Jr. Model between 1954-56. In 1957 the model name was changed to "Skylark". During its tenure of 1954 until the late 60's the GA-5/GA-5T
was probably Gibson's most popular model of amplifier. There were several very different
Gibson amps that wore the "Skylark" name over the years.  Below are pictures and data
on some of the styles of Gibson Skylark. There may be others.
Figure 1

 Before the Skylark, one of Gibson's small amplifier offerings was the Gibsonette. They also were produced in several styles over the years (including styles as in Figures 2 and 3).

The style shown at left (see figure 1) was made in 1952-53. It has a 10" Jensen field coil speaker and a tube compliment of: 1-6SJ7 (pre amp)
2-6V6 (power amp; run in a parallel, single ended design)
1-5Y3 (rectifier)

The controls were located at the bottom rear of the cabinet directly on the chassis and consist of: 2 input jacks, on/off switch and a volume control.
Figure 2

 This is a beautiful example of the earliest style GA-5, made in 1954-56 these first three years the GA-5  model designation was "Les Paul Junior". The Skylark name came in 1957. Note the "TV" front panel (see Figure 2).

This model had a 10" Jensen  speaker and a tube compliment of: 1-6SJ7 (pre amp)
1-6V6 (power amp)
1-5Y3 (rectifier)

The circuit in these is very nearly the same as the Fender 5C1 model "Champ".

The controls were mounted on a slanted panel at the upper rear and consist of: 2 inputs, volume control, fuse holder, on/off switch and a jeweled pilot light.

Figure 3

 Beginning in 1957 until 1961 the first true "Skylark" model was introduced. Note the blond  tolex and the disappearance of the "TV" styling (see Figure 3). Some Gibson models sported a "tweed" looking vinyl covering in 1960-61, but not the Skylark.

Through these years the Skylark featured a 8" Jensen "special design" speaker. Tube compliment for GA-5:
1-12AX7 (pre amp)
1-6V6 (power amp)
1-5Y3 (rectifier)

The GA-5T of this period used:
1-12AX7 (pre amp)
1-6BM8 (power amp and tremolo)
1-5Y3 (rectifier)

Like the earlier Les Paul Junior, the controls were mounted on a slanted panel at the upper rear and consist of: 2 inputs, volume control, fuse holder, on/off switch and a jeweled pilot light.
Figure 4

Figure 5

 In 1962-?? Gibson introduced the "Crestline" models, and the venerable Skylark got a complete re-design and significant circuit changes, including the addition of a tremolo circuit in the GA-5T.
The T in the model number stands  for "Tremolo" (see Figure 4). The GA-5 minus the tremolo was still available (see Figure 5).
 
Note the differences between the rough, dark, black "elephant hide" tolex and silver grill cloth on the GA-5T (Figure 4), and the
very dark brown, wood grain imprint tolex and rectangular  patterned brown grill cloth on the GA-5 (Figure 5 ). Whether these differences were specific by model (GA-5/GA-5T) or a mid model/year update is an unanswered question.
 
The changes included: a 10" Gibson Ultrasonic speaker and a tube compliment for the GA-5T of:
2-6EU7's (pre amp/ phase inverter and tremolo)
2-6AQ5's (in a push-pull power amp design)
1-6X4 (rectifier)

The GA-5  tube compliment during this period was:
1-6EU7 (pre  amp)
1-6C4 (phase inverter)
2-6AQ5's (in a push pull power amp design)
1-6X4 (rectifier)

With this design, the tubes were mounted horizontally on the back of the chassis (top of tubes pointed to rear).
Approx. size is 20.25" x 15" x  6.5".

The controls, now located on a sloping *front* panel, are; 2 inputs, volume, rotating on/off knob, jewel pilot light and fuse holder. The GA-5T includes a frequency control knob to control tremolo speed.
Figure 6

 In 1965 and 1966 Gibson gave the Skylark another major design overhaul. These are commonly referred to as "white panel" amps.
These are notable for their rough black "elephant hide" tolex, silver grill cloth, and Fender style 1-10 marked knobs
(see Figure 6).

These featured a 10" Gibson Ultrasonic speaker. The tube compliment for the GA-5 in this series is:
1-6EU7 (pre amp)
1-6BQ5 (power amp)
1-6X4  (rectifier)

The GA-5T used:
1-6EU7 (pre amp),
1-6C4 (phase inverter),
2-6BQ5  (in a push-pull power amp design)
solid state rectification via 2 diodes.

Control panel layout is: 2 inputs, volume, treble, bass, speed and frequency (tremolo), and a rotating on/off knob with a small pilot light above it (the fuse holder is on the back panel).

It is notable that this design used a box type chassis that is attached to the cabinet by screws through the top like the 60's
Fender amps. Also, the tubes hang down from the chassis.
Figure 7

 In 1967-?? Gibson changed the design again to the Medalist? series styling? (see Figure 7).

These have the 10" Gibson Ultrasonic speaker and a tube compliment of:
2-12ax7's (pre amp and tremolo)
1-6BQ5 (power amp)
1-6X4 (rectifier)

Control panel includes: 2 inputs, tone, tremolo knob (controls speed), rotating on/off switch and a pilot light.

Gibson Skylark EH-500 lap steel, 1956-1968, Eight string version available in 1958. Korina wood body.

Gibson amps, were often sold as a companion to (surprise!) a Gibson guitar or lap steel.
 
Notice:
 These are the Gibson GA-5/GA5-T models that I am aware of. There may be others, and I cannot
 attest to the validity of the specifications. If anyone knows of any other models or specs (verifiable by
pictures or schematics), can verify this information, or has verifiable information that is different from this,
please contact me and I'll add to / change  this page.

By: John King
kingsx@swbell.net
11/12/02