7
4
O
PERATING
D
ETAILS
4.1
H
IGH
-B
IAS
M
ODE
The high-bias class-AB output stage in the Minotaur can operate in two modes, “normal” and “high-
bias”. By default, the amplifier operates in normal mode, operating in class-A up to about 1 W per
channel into an 8-Ω load. In high-bias mode, the output stage quiescent current is increased so that it
operates in class-A up to about 5 W per channel into an 8-Ω load.
The amplifier can be placed in high-bias mode during turn-on. Starting with the amplifier in “sleep”
mode (red “sleep” LED on), push and hold the “5” switch while pressing the ON-OFF switch. Release
both buttons after the amplifier turns on. An amber LED behind the vacuum tubes indicates that high-
bias mode has been turned on. The high-bias mode is retained for subsequent operation after the
amplifier is switched off; to return to normal mode, once again press and hold the “5” switch while
turning the amplifier on with the ON-OFF switch.
The amplifier dissipates considerably more power in high-bias mode, and you should expect the external
temperature of the cabinet to be noticeably warmer in this mode. It is even more essential that you
provide good ventilation for the Minotaur when it is operated in high bias mode. You may notice the
cooling fan come on if ambient temperatures are high or ventilation is suboptimal.
The bias point in normal mode has been selected carefully in both listening tests and measurements as a
good compromise between performance and heat production; there is minimal improvement with
increased bias, and most listeners do not notice any difference with high-bias mode. But depending on
your listening environment, speaker efficiency, and program material, you may prefer high-bias mode
for critical listening, reverting to normal mode for casual listening.
4.2
A
UTOMATIC
P
OWER
O
FF
The Minotaur monitors input signal level and is programmed to shut itself automatically after 30
minutes if it fails to detect a signal at the selected input (the volume control position does not affect
this). This is done to save power and prolong tube life.
The automatic-power-off setting can be disabled during turn-on. With the amplifier in “sleep” mode (red
“sleep” LED on), press and hold any of the source buttons except “5” (that is, MUTE or 1-4) while
pressing the ON-OFF button (this key combination also works with the remote control). The red ON-OFF
switch will flash twice slowly to indicate that automatic-power-off has been disabled. During each
subsequent turn-on, the ON-OFF switch will flash to remind you that automatic-power-off has been
disabled.
