16
Tube Locations
The diagram below shows the location of the tubes on the amplifier chassis:
12AX7 Tubes
The preferred brand for 12AX7 tubes is the TAD 12AX7A-C. Many of the Russian made 12AX7
tubes (such as the Tung Sol and EH brand 12AX7s, and the Sovtek 12AX7LPS) will fail when used
as a cathode follower, and therefore they are not recommended for use in the U1 position.
NOTE: Although the U1 position is specified as 12AX7, the circuitry has been designed so that a
12AU7 tube may be used instead, for lower gain and more headroom. If you primarily play
clean without overdrive, you may prefer to use a TAD 12AU7 in the U1 position. It will
significantly increase clean headroom and deliver a fuller, fatter sound.
12AU7 Tubes
The preferred brand for 12AU7 tubes is the TAD 12AU7A. This brand offers better sound and
reliability than the Tung Sol 12AU7.
6V6 Tubes
The preferred brand for 6V6 tubes is the TAD 6V6GT-STR. When replacing 6V6 tubes, no biasing
is necessary. The output tubes are cathode biased and have no bias adjustment.
Rectifier Tubes
The preferred brand for the rectifier tube is the TAD 5Y3GT.
U1
TAD 12AX7A-C
1
st
Gain Stage + Cathode Follower
U2
TAD 12AU7
2
nd
Gain Stage + Cathode Follower
U3
TAD 12AX7A-C
3
rd
Gain Stage
U4
TAD 12AU7
Phase Inverter
U5, U6 TAD 6V6GT-STR Output Tubes
U7
TAD 5Y3GT
Rectifier
