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7. TUBES
There is an upper adjustment limit to the "high" BIAS setting, which is indicated by the green and red
LEDs lighting up at the same time, and a lower limit to the "low setting, where the yellow and green
LEDs light up. The lower limit should be used with "smaller" output tubes such as the EL 34 and
similar. The upper value, which provides a higher BIAS current for the output tubes, should be used
with the more powerful tube types such as the KT88, KT100, 6550, KT90 (see chapter 7.2).
These tube types do not have to be operated at a high BIAS setting; they will work perfectly well on
the low setting. However, certain loudspeakers may benefit from the higher BIAS current, as it will
increase the damping factor and provide slightly better control of the movement of the speakers.
LED graphs
Important note:
If the protection system is activated, adjusting the BIAS is impossible. The BIAS display
always indicates yellow. Please do not turn the regulators in this mode (see chapter 6.1).
BIAS
yellow
green
red
BIAS
low
BIAS
high
Brightness
of the
LEDs
lower usable
range of
adjustment
upper usable
range of
adjustment
