Quicksilver ships the KT Mono Amplifiers with matched KT88 tubes but any KT series output
tubes can be used. The output tubes should be matched.
Output tubes will need to be replaced periodically. When a degradation in sound occurs, the fuse
blows repeatedly, or the tubes will not hold their bias anymore, it is time for new output tubes.
We recommend purchasing tubes from Quicksilver Audio or your dealer and we recommend
keeping extra fuses and an extra output tube on hand.
OUTPUT TUBE BIAS SETTING
Output tube bias should be set immediately when new tubes are put in; then again in 15 minutes;
and periodically the first few times of using the amplifiers. After that the bias should be checked
monthly.
The bias control is located between the output tubes near the power transformer.
To adjust the bias you will a slot-head screwdriver and a multimeter that reads millivolts. Adjust
by turning clockwise to increase bias; counterclockwise to decrease bias.
Set the meter to read millivolts (not milliamperes.) Insert the black and red probes from your
meter into black and red pin jacks on the amp. The millivolt reading on the meter is actually the
bias current in ma through the output tubes. Efficient speakers will sound better with lower bias
(60ma) and inefficient speakers may require higher bias (80ma.) Bias should not be set higher
than 100ma.
If the bias cannot be set low enough, then an output tube may be shorted and the amplifier should
be turned off immediately. If the bias cannot be set high enough, then one output tube may be
dead. In either case, the output tubes need replacing. Replace the output tubes as matched pairs—
matched pairs will sound better and last longer.
KT Mono Amplifier
Fuse
4 amp
slo-blo
4 ohm
Ground
8 ohm
12AX7 12BH7
