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TUBES &
BIASING
POWER TUBES
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Our high wattage amplifiers are designed around 6L6
tubes - but will accept the following tubes & gladly
display their tonal characteristics for you in your Revv.
KT88
This tube is punchy with a strong low end and great
clarity. The extra power out of this tube adds extra
headroom & is very tight & focused. Overall can be
described as “more” of the same sound, with a focused
attack.
EL34
The EL34 tubes are more aggressive than the KT88,
they add more harmonic content & have a bit more
sizzle on the highs. Can impart a slightly “British”
classic flavor.
6L6GC
Our standard, the 6L6GC tube is big, open & articulate.
Note:
The tubes listed above are guaranteed to bias
correctly & sound good in the amplifier, but if you
are an experienced technician other tubes can be
experimented with as well. 6550, KT77, KT66, 5881 can
be equipped, with care.
POWER TUBE SOCKETS
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This amp has been designed to allow mixing of power
tubes as each pair has its own bias adjustment. Tube
positions 1 & 3 are set up as one pair & are biased with
the bias adjustment trimmer in between them. Tube 1
and 3 are the pair of power tubes closer to the middle
of the amplifier. Tubes 2 & 4 are the second set that are
biased with the adjustment trimmer in between them.
This pair of power tubes are found closer to the rear
of the amplifier. This allows you to mix different power
tubes in the amp if you wish to experiment with new
sounds. i.e. a set of KT88 tubes can be used with a set
of EL34 tubes.
Note:
While we designed the amplifier to be easy
to maintain, we advise that all tubes be set up by a
qualified service technician to prevent damage to the
amp from improper bias settings.
PREAMP TUBES
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This amplifier uses 12AX7 (ECC83) preamp tubes in the
preamp of your amplifier. Preamp tubes do not need
to be biased & usually have a long life unlike power
tubes, but a preamp tube can become faulty at any
stage of its rated lifespan.
POWER TUBE BIAS
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You will need a voltmeter or digital multimeter set to
the lowest DC voltage range. (Make sure you refer to
the meter’s user manual).
Note:
Use tubes that are matched! If 2 different tube
types are being used, make sure they are matched. If all
4 are the same type, make sure they are matched pairs
(don’t mix them) although a matched quad is better.
To prepare:
1.
Remove the rear baffle cover from the rear of the
amplifier. If you are replacing tubes, do so now with
the power off & the amplifier unplugged from the
main power receptacle. Place the new tubes in the
correct socket positions.
2.
Turn the trimmers down by turning the trim pot
with a small screwdriver in the counterclockwise
direction. You can access the trim pots through the
small holes in between the power tube pairs. If any
fuses had blown, make sure to replace them as well.
