Sunn 021-3303, Instruction Manual, Page: 6 / 28

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Q. MAIN AMP OUT - This 1/4 inch, unbalanced, TS, output
jack is designed to send a preamp line level signal from your
“main” Model T amplifier to another Model T amplifier. This
jack is used for chaining multiple Model T amplifiers togeth-
er and increasing your on stage volume. Do so by inserting
a 1/4” cable from the main amp out jack into another Model
T’s ext amp in jack.
R. EXT AMP IN - This 1/4 inch, unbalanced, TS, input jack is
designed to receive a preamp line level signal from another
Model T amplifier. This jack is used for chaining multiple
Model T amplifiers together and increasing your on stage
volume.
S. FOOTSWITCH (INCLUDED) - Plug-in connection for the
footswitch. The footswitch allows the remote on / off selec-
tion of the effects loop and switching of the two channels.
Using the footswitch overrides the rear panel effects loop
switch and the front panel channel select switch.
T. XLR LINE OUT - This balanced XLR male line level output
is designed to feed the Model T’s signal to an external
power amplifier or main house mixer.
U. EXTERNAL SPEAKER JACK - Plug-in connection for an
additional speaker enclosure. This jack is wired in parallel
with the main speaker jack and must ONLY be used in con-
junction with the main speaker jack. If this jack is used with-
out the main speaker jack, no sound will be produced.
V. MAIN SPEAKER JACK - This is the main plug-in connec-
tion for your speaker enclosure and should always be used
as the primary connection. If your Model T is in the on and
ready to play position, make sure a load of at least 4
Ω
is
present. Failure to do so may result in your Model T being
damaged by using an improper impedance load. As a rule
of thumb, ALWAYS connect or disconnect any speaker
enclosure to your Model T with the power off.
W. LOAD IMPEDANCE - This switch allows the selection of
d i ff e rent
impedance loads for your loudspeaker
enclosure(s). Make sure to match the total speaker’s load
impedance to the load impedance selector switch setting.
Failure to do so may result in your Model T being damaged
by using an improper impedance load.
Tube life varies depending upon playing style and applica-
tion. Power tubes have a much shorter life than pre-amp
tubes which can last for years. For continued optimum per-
formance from your amplifier, the tubes should ONLY be
replaced with the same type tubes as specified below.
IMPORTANT: ALWAYS unplug the amplifier before chang-
ing tubes and remember that THE TUBES ARE HOT! Wait
for the tubes to cool before handling them.
A simple way to check if the tubes are worn is to replace the
set in your amp with your spare set and listen for improve-
ment. (You carry a spare set of tubes and fuses, don't you?)
• First, replace the OUTPUT tubes with new tubes; re-bias
and listen (bias/balance instructions are on the next page).
• Next, re-insert the ORIGINAL OUTPUT tubes and re-bias.
Replace the PRE-AMP tubes with new tubes and listen.
• Finally, try replacing both the OUTPUT (re-bias) and PRE-
AMP tubes with new tubes and listen.
If there is a marked improvement in the tone of your amp at
any point in this procedure, leave the new tubes in your amp
and purchase another spare set.
The Model T's tube complement consists of:
• Four 6L6GC tubes at V7,V8,V9 and V10 (part #053980),
• Two 12AX7A tubes at V1 and V2 (part #023572),
• Four 12AX7WA tubes at V3, V4, V5 and V6 (part #013341).
12AX7WA 12AX7WA
12AX7WA 12AX7WA