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REAR PANEL FEATURES CONTINUED
4. Line Out Jack: The preamp Line Out is in parallel with the Effects Loop Send and Return jacks, it can be used to send a tube-buffered low-
impedance (unbalanced) signal to other equipment such as mixing consoles or other amplifiers. Multiple Special 12/20 amplifiers can be linked
by connecting the Line Out jack to the Effects Return of the second amplifier. Several Special 12/20's can be linked in this manner, with the
first amplifier's preamp serving as the master preamp for all additional amplifiers.
5. Impedance Selector: This 3-position slide switch selects the appropriate output impedance to match your speaker cabinet's impedance.
6. Speaker Output Jacks: These two jacks are wired in parallel. The Special 12/20 combo has a 16-ohm speaker that is connected to the
internal speaker jack. The combo's speaker remains connected when using the external Speaker Output jacks. When using the combo with an
additional speaker cabinet, switch the Impedance selector to 8 ohms.
7. Power IEC Receptacle/Line Voltage Selector: Your amplifier will ship with the correct voltage setting, fuse and AC plug type for your
region. When traveling to different countries, remove the plastic protector and select the appropriate voltage. For lowest noise and safest
operation, always use the correct plug type for your region/country, and always provide the amplifier with proper AC grounding.
8. 12/20-Watt High/Low Power Voltage Selector: Located behind the rear panel, this switch selects the appropriate maximum voltage for
each output tube type. Set it to the 20-watt High Volt position when using 6L6 or EL34 output tubes. Set it to the 12-watt Low Volt position
when using 6V6 or EL84 output tubes. (EL84 output tubes require 6V6-to-EL84 adapters.)
Special 12/20 Block Diagram
Input
Input Stage
Tone Stack
Pull Boost
Volume
Tone
E ects Loop Bu er
Send Level
7
BLOCK DIAGRAM
Line Out
V5
Output Tubes
Send
Return
Return
Return Level Voltage Ampli er Cathode Follower
Phase Splitter
V4
-6
-6
-8
-8
-10
-10
-12
-12
-14
-14
-16
-16
-18
-18
-20
-20
-22
-22
-24
-24
d
d
B
-26
-26
r
-28
-28
-30
-30
-32
-32
-34
-34
-36
-36
-38
-38
-40
-40
-42
-42
-44
-44
-46
-46
-48
-48
20
Watts
Depth
Texture
Speaker
BOOST — ON/OFF
50
100
200
500
1k
Hz
-6
-8
-10
-12
-14
-16
-18
-20
-22
-24
d
-26
B
r
-28
-30
-32
-34
-36
-38
-40
-42
-44
-46
-48
2k
5k
10k
20k
8
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