Gibson GA-20 User manual

GA-20, GA-40 &
GA-42 AMPLIFIERS
OWNER’SMANUAL

IMPORTANT SAFETY INSTRUCTIONS
WARNING:TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE
THIS APPARATUS TO RAIN OR MOISTURE AND OBJECTS FILLED WITH LIQUIDS,
SUCH AS VASES, SHOULD NOT BE PLACED ON THIS APPARATUS.
The lightning bolt warns of the risk of shock from high voltage. Do not tamper with
or attempt to open any areas where this warning is present.
The exclamation point alerts the user to an important operating or maintenance
instruction.
Conforms to EU directives.
Conforms to North American standards
Earth Ground
Do not place in Municipal Waste Disposal. Please recycle appropriately.

1. Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with dry cloth.
7. Do not block any ventilation openings. Install in accordance with the manufacturer's
instructions.
8. Do not install near any heat sources such as radiators, heat registers, stoves, or other
apparatus (including amplifiers) that produces heat.
9. Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized
plug has two blades with one wider than the other. A grounding type plug has two
blades and a third grounding prong. The wide blade or the third prong are provided for
your safety. If the provided plug does not fit into your outlet, consult an electrician for
replacement of the obsolete outlet.
10. Protect the power cord from being walked on or pinched particularly at plugs,
convenience receptacles, and the point where thy exit from the apparatus.
11. Unplug this apparatus during lightning storms or when unused for long periods of time.

12. Refer all servicing to qualified service personnel. Servicing is required when the apparatus
has been damaged in any way, such as power-supply cord or plug is damaged, liquid has
been spilled or objects have fallen into the apparatus, the apparatus has been exposed to
rain or moisture, does not operate normally, or has been dropped.
Importanti istruzioni di sicurezza
Tenere l’apparecchio lontano da gocciolamenti o schizzi. Evitare di appoggiare recipienti pieni
di liquido sull’apparecchio.
Collegare l’apparecchio solo a prese di corrente dotate di messa a terra di protezione.
La spina all’estremità del cavo elettrico è il dispositivo che consente di scollegarsi dalla rete.
“Rete” è il termine ufficiale per designare la fonte di alimentazione elettrica. Inserire la spina
nella presa in modo da consentirne sempre un facile accesso.

L’interruttore attiva e disattiva (ON e OFF) l'amplificatore. Quando l’amplificatore viene
acceso, la spia si illumina. Con l’interruttore in posizione OFF, l’amplificatore è ancora
collegato alla rete.
Wichtige Sicherheitsinformationen
Setzen Sie dieses Gerät nicht in einer Umgebung ein, in der tropfende oder spritzende
Flüssigkeiten auftreten könnten. Stellen Sie keine mit Flüssigkeiten gefüllte Objekte wie zum
Beispiel Vasen auf das Produkt.
Benutzen Sie für dieses Produkt nur eine geerdete Steckdose.
Mit dem Stecker der Anschlussschnur können Sie die Verbindung zum Stromnetz
unterbrechen. Achten Sie deshalb darauf, dass der Stecker jederzeit leicht zugänglich ist.
Mit dem Ein-/Ausschalter schalten Sie den Verstärker EIN (ON) und AUS (OFF). Bei
eingeschaltetem Verstärker leuchtet die Kontrolllampe. Wenn der Schalter sich in der

AUS-Position befindet, ist der Verstärker nicht vom Stromnetz getrennt.
Importantes instrucciones de seguridad
No exponga este producto a goteos ni salpicaduras. No coloque objetos llenos de líquido
sobre este producto, como por ejemplo un jarrón.
Conecte siempre el producto a una toma de corriente que tenga una conexión a tierra de
protección.
El enchufe del cable es el dispositivo de desconexión de la red eléctrica. "Red eléctrica" es el
término oficial para la fuente de alimentación eléctrica. Mantenga siempre asequible el enchufe
del cable.
El interruptor enciende (ON) o apaga (OFF) el amplificador. El indicador luminoso se
enciende cuando el amplificador está encendido.Cuando el interruptor está en la posición
OFF (apagado), el amplificador no está desconectado de la red eléctrica.

Consignes importantes de sécurité
Ne pas exposer ce produit à des suintements ou des éclaboussures. Ne pas poser des objets
remplis de liquides, tels des vases, sur le produit.
Brancher toujours le produit à une prise électrique qui possède une prise de protection à la
terre.
La fiche d’alimentation électrique est le dispositif du réseau électrique pour débrancher. Le
“réseau électrique” est le terme officiel pour la source d’alimentation électrique. Conserver
toujours la fiche d’alimentation électrique facilement accessible.
L’interrupteur allume (ON) et éteint (OFF) votre amplificateur. Le voyant lumineux s’allume
lorsque l’amplificateur est allumé.Votre amplificateur n’est pas déconnecté du réseau
électrique lorsque l’interrupteur est en position ARRET (OFF).

CONGRATULATIONS ON YOUR NEW
GIBSON HANDBUILT SERIES AMPLIFIER
As the new owner of a Gibson amplifier, you have joined a great Gibson legacy. When the
electric guitar emerged in the 1930s as an instrument with its own voice, Gibson amplifiers
powered that voice. In the 1940s and 1950s, Gibson’s continuing advances in amplifier design
matched the company’s celebrated guitar innovations. Over 60 years later, in 2004, Gibson
Labs introduced its most prestigious range of amplifiers to date; the Gibson Handbuilt Series.
Each Handbuilt amplifier represents an uncompromised approach, from design to manufacture.
From the all-tube circuit path, to the meticulously hand-wired turret board, every aspect
of your new amplifier has been brought to you with no less a mission than to build the very
best in professional amplification. Built into every Gibson Handbuilt amplifier is a respect
for the simplicity that creates long-lasting, superior tone. You’ll hear it in the natural
responsiveness to your play, the rich tone and see it in the top quality cabinetry, tolex
and overall attention to detail.

We invite you to plug in, turn up, express yourself and become a part of a great Gibson
tradition.
If you ever have a question or concern about anything, any day, any time, please call Gibson
Customer Service at 1-800-4GIBSON (444-2766) or email ser[email protected].
From the Gibson Tone Team at
Gibson Labs Technology Group
Suite 330
159 South Jackson Street
Seattle,WA 98104
www.gibsonamps.com

Input Jack 1
Mix Input
CHANNEL 1
Volume Treble Bass
CHANNEL 2
Volume Treble BassMiddle Reverb
TREMELO
Speed Depth
Play/Standby
On/Off
Input Jack 2
The GA-20RVT

FRONT PANEL
Input 1: Accesses the first channel of your amplifier. This is the more aggressive channel that
provides less headroom before overdrive. This channel offers Treble and Bass Controls.
Input 2: Accesses the second channel of your amplifier. This is the cleaner channel that
provides a rich clean tone, breaking into subtle overdrive later, as you increase the channels
volume.
Mix Input: Unique to the Handbuilt Series, the Mix input allows you to combine the signals
of both channels 1 & 2. This is useful for creating a wide range of tonality, mixing clean and
overdrive or adding reverb to the overdriven tone of Channel 1.
Note: Channel selection and the mix input can be accessed and toggled between with any
A-B-Y pedal available at most musical instrument dealers.
Reverb: Your amplifier’s spring reverb unit is “live” on Channel 2, but can affect Channel 1
via the Mix input. The Handbuilt Series features Tube-Driven Reverb for a more natural,

smoother reverb effect. A clockwise turn increases the reverb “tail;” a counter clockwise
turn decreases the reverb tail. At 7 o’clock, the Reverb effect is off.
Tremolo: Creates an intermittent signal effect (think surf music) with variable Speed and
Depth Controls.
Speed: Determines the rate at which the signal fluctuates in volume.
Depth: Determines the subtly or severity of the signal fluctuation.
On/Off: Turns your amplifier on or off. We recommend that you have your “Play/Standby”
switch in the “Standby” position when powering up. This helps preserve tube life.
Play/Standby: Allows you to idle your amplifier in “Standby” mode (no signal output) or Play
your amplifier in “Play” mode (signal output).

REAR PANEL
Footswitch: Accepts the 2 button footswitch that shipped with your amplifier. Reverb and
Tremolo are turned on or off with these buttons.
Pentode/Triode Switch: In Pentode Mode, your amplifier will run in full power, providing
higher output. In Triode Mode, your amplifier will run at about 1/2 power. This feature further
enhances the flexibility of the Handbuilt Series. With it, you essentially have two amplifiers.
For classic to modern rock styles, the high power output will perform with a more aggressive
overdrive. In low power, Jazz and Blues styles benefit from more reaction to your playing
attack, allowing you to “squeeze” overdrive out or maintain a thick “punch.”
For more information on Class A, visit our website at
www.gibsonamps.com and click on our Amp Academy Sessions.
Speaker Outputs: There are 4 speaker outputs on the rear panel of your amplifier; 8 ohm,
16 ohm and (2) 4 ohm outputs. These allow you to send a powered signal from your
amplifier to an extension cabinet(s). To insure the safety of your amplifier and other devices,

be sure to use a quality, unshielded speaker cable and only connect to speaker cabinets which
are rated equal to the output jack you are using. For example: a 4X12 speaker cabinet, rated
at 16 ohms, should ONLY be connected via the “16 ohm” output jack on the rear of your
amplifier.
Main Fuse — GA-20
100V~/120V~ (Japan/U.S.A) use 5 x 20mm T1.6AL250V (Slo Blo) fuses.
230V~ (Europe/U.K.) use 5 x 20mm T800mAL250V (Slo Blo) fuses.
Main Fuse — GA-40 and GA-42
100V~/120V~ (Japan/U.S.A) use 5 x 20mm T1.6AL250V (Slo Blo) fuses.
230V~ (Europe/U.K.) use 5 x 20mm T1.25AL250V (Slo Blo) fuses.
Power Cord Connection
Your amplifier shipped with a power cord appropriate for the country in which you purchased
it.

OPERATING INSTRUCTIONS
PLUG YOUR AMP IN
CAUTION: The power cord plug is the designated mains disconnect device.“Mains”
is the official term for the electrical power source.Visually inspect the power cord
plug for damage before each use. Do not use it if it appears damaged. Keep the power
cord plug accessible at all times.Always use a grounded/earthed AC socket. Never use
a socket adapter that will not ground the amplifier.To reduce the risk of fire or
electrical shock, do not expose your amplifier to rain or moisture.
NOTE: Your Gibson amp is configured for the line voltage normally appropriate for the
country in which you purchased it. 115V for U.S., 100VAC for Japan, and 230V for all other
countries.
To check the line voltage setting, note the voltage setting visible through the window in the
power line fuse compartment cover on the back of the amp.

To change the line voltage setting:
1. Disconnect the power by removing the power cord from both the power outlet and the
amplifier.
2. Open the fuse compartment by inserting a screwdriver blade gently into the tab at the
bottom of the compartment and prying until the tab can be removed with the fingers.
3. Remove the line voltage selector assembly by gripping the line voltage indicator tab with
pliers and pulling it straight out of its connector.
4. Rotate the line selector assembly to the desired voltage and reinsert.
5. Verify the appropriate fuse for the selected line voltage and reinsert the fuse
compartment by pushing it back into place until the tab locks.
SWITCH IT TO “STANDBY”
Standby allows your amplifier to “warm up” before you activate its output as well as sit in an
idle position (no output but the amp is still on). This preserves tube life and allows you to
bypass output when desired.

TURN IT ON
The Power Switch turns your amplifier ON and OFF.The “On/Off” switch glows when the
amplifier is turned on.
CAUTION: Your amplifier is not disconnected from the mains when the Power Switch
is in the OFF position.
PLUG YOUR GUITAR IN
First, turn the Volume knobs down – counterclockwise – as far as they will go.Then plug
your 1/4 inch plug (standard guitar cord) into one of the three inputs as described in the
“Front Panel” overview earlier.
SWITCH FROM “STANDBY” to “PLAY”
Make sure your volume is turned down before switching from “Standby” to “Play.” This avoids
sudden output which could harm your speakers.

TURN IT UP
Gradually turn your volume up to a desirable level.
MORE TECHNICAL INFORMATION
CIRCUIT TOPOLOGY
GA20RVT: Class A 15W
GA40RVT & GA42RVT: Class A 30W
INPUTS
Channel1, Channel 2 & Mix
TUBES/VALVES
GA20RVT: 5X12AX7 (Preamp), 2X6L6 (Power)
GA40RVT & GA42RVT: 5X12AX7 (Preamp), 2X6V6 (Power)
FUSE
The line fuse, located in the line voltage module on the back of the amp,protects your
amplifier against irregularities in the A.C. source, tube failure, component failure, severe

overload to the output amplifier and other conditions that can be unsafe or damaging to
the amplifier. If your amplifier continually blows the line fuse, there is a problem that must
be corrected before the amplifier is put back into service. Contact an authorized Gibson
Amplifier Service Center. See above for replacement fuse specification.
To replace the fuse, first remove the power cord.Then use a thin blade prying tool to pop
out the fuser holder. Remove the old fuse and put the new fuse in the holder. Push the holder
in until it snaps into place.
NOTE: Never replace the line fuse with a higher amperage rating. It is not only unsafe, but it
leaves your amplifier unprotected in the event of a tube or component failure and invalidates
your warranty.
SPEAKER
The GA20RVT, GA40RVT & GA42RVT come equipped with 12” Eminence Legend Speakers.
The GA20RVT & GA40RVT come with a single speaker, while the GA42RVT comes with two.
Your GA20RVT or GA40RVT feature asymmetrical speaker placement (set off to one side).