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7. TUBES
7.3. BIAS measurement facility
The BIAS measurement facility makes it easy for you to check and adjust the idle current of the
output tubes. Getting the BIAS setting right for all four tubes is critical for both the sound of the
power amplifier section and for the service life of the tubes. This feature guarantees consistent
sound quality over the entire lifetime of the output tubes.
That is why we have built this BIAS measurement facility into the RE 290 – to allow you, the user,
to carry out the adjustment yourself without the need for test equipment. The use of precision op
amps makes it possible for you to set the BIAS to accuracy within 0.2%, making it superior to any
other method.
Using selected output tubes only makes sense if the idle current is adjusted accurately, as is
clearly shown in Fig. 1 Technical Data.
The LED display:
Ecomode LED indicates the status of the Ecomode Electronic
Yellow - LED indicates that the BIAS is Low
Green OK LED indicates that the BIAS has the correct value
Yellow + LED indicates that the BIAS is too high
Red OFF LED indicates that the Protection Electronic has turned off the Power supply of
the Tube section
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