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Each 12AX7 has two sections/functions. Section A is shown first, Section B is second. Factory recommended
tubes are listed under each location. Numbering sequence is right to left looking at back of amp starting with
the row closest to front panel of amp.
V1 (shielded tube)
12AX7WB Sovtek
12AX7 China Selected
V2
12AX7 China
V3
12AX7 China
V4
EF86/6267
V5
12AX7 China
V6
5U4GB Russia
5U5G China
V6-9
EL34B-STR
EL34 SED
EL34 Svetlana
EL34EH
Page 3
PITTBULL FIFTY/CL
TUBE FUNCTION AND LOCATION CHART
Input Gain Stage 1 and signal splitter for both channels
Gain Stage 2 for Green channel
Use in place of WB if more gain is required.
Gain Stage 2 for Red channel
Gain Stage 4 for Red and Green channels. Active when either Gain Switch is set to
HI.
Gain Stage 3 for Red and Green channels
Tone Control Driver for Red and Green channels.
Reverb Driver. Small Signal Pentode. Reverb Option Only (Earlier versions used
EL84). Not interchangeable with 12AX7 or EL84
Phase Inverter
Rectifier Tube
Power Tubes
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