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7. TUBES
7.3. THE BIAS MEASUREMENT SYSTEM
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 V 70 SE – 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 an
accuracy
within 0.3%, 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.
V 1
V 2
V 3
V 4
Regler für Röhre
V1 V2 V3 V4
rot grün gelb
How to set the BIAS
Turn the Input selector knob [2] clockwise to the BIAS position to activate the measurement
circuit.(pos. 6); Signal/input selection is disabled. The 3 LEDs above each screw in the display
panel show whether the BIAS setting is too low, correct, or too high. Use the small screwdriver
supplied to adjust the BIAS.
To increase the BIAS current to each output tube, turn the screwdriver clockwise.
The adjusting screws are fully insulated. There is no risk of electric shock and the adjustment
procedure is completely safe.
The LED display:
Red LED only
Setting is too high
Green + red LED
Setting is OK for KT 88 6550, etc. = high BIAS
Green LED only
Setting is OK.
green LED
Setting is OK for EL 34, 6L6, KT 66, etc. = low BIAS
Yellow LED
Setting is too low
Summary of Contents for v70se
Page 1: ...V 70 SE ...
