4
13. Replacement Tubes and Bias
Your YBA is supplied with factory-matched output tube pairs. When
tube replacement becomes necessary, replace the output tubes with
matched pairs to maintain the highest performance of your amplifier.
It is only necessary that the individual pairs be matched to each other.
The YBA300 does not need 12 matched tubes, just 6 matched pairs.
The YBA100 does not need 4 matched tubes, just 2 matched pairs.
Note: When changing output tubes adjust the bias so that the indicator lights on the rear do not glow. A blue
light indicates the bias is set too low, a yellow light indicates the bias is set too high. All of the red lights and all
of the blue lights will light when the amplifier is in standby mode. This is because all of the tubes are locked
out and the bias is zero. If a red light is illuminated when the amplifier is in “operate” mode, this indicates an
overcurrent condition with that tube pair and it is currently “locked out”. The amplifier will continue to operate with
the remaining pairs. The standby switch will reset the lockout relays. If the “lockout” condition persists, that pair
of tubes will need to be replaced.
On the YBA300, if you decide to swap your tubes and put in 6L6 or EL34s, just remove the double-sided plate
and reverse to signify the change.
The power tubes are accessible through either the top or the back grille. The pre-amp tubes are accessible through
the grille on the bottom of the YBA300. A Phillips screwdriver is all that is needed to remove any of the grilles.
Bias
High
Low
Protect
A
Bias
High
Low
Protect
B
Bias
High
Low
Protect
C
Bias
High
Low
Protect
D
Bias
High
Low
Protect
E
Bias
High
Low
Protect
F
Bias
High
Low
Protect
A
B
Bias
High
Low
Protect
POWER
PREAMP
SPLITTER
EL34
V1C
EL34
V1D
EL34
V1E
EL34
V1F
EL34
V1A
EL34
V1B
EL34
V2C
EL34
V2D
EL34
V2E
EL34
V2F
EL34
V2A
EL34
V2B
12AX7
V3
12AX7
V4
12AX7
V5
DRIVER
12AU7
V6
TRAYNOR YBA300
POWER
PREAMP
SPLITTER
6L6
V1C
6L6
V1D
6L6
V1E
6L6
V1F
6L6
V1A
6L6
V1B
6L6
V2C
6L6
V2D
6L6
V2E
6L6
V2F
6L6
V2A
6L6
V2B
12AX7
V3
12AX7
V4
12AX7
V5
DRIVER
12AU7
V6
TRAYNOR YBA300
1/4-inch T.R.S.
Phone Plug
Balanced 1/4-inch T.R.S. to Balanced XLR
XLR Plug
(Male)
Tip = 0°
Ring = 180°
Sleeve = Ground
1
Pin 1 = Ground
Pin 2 = 0°
Pin 3 = 180°
2
3
