TUBES
The input tubes in this amplifier were chosen for their specific performance characteristics. These
tubes should last between one and two thousand hours. We can only guarantee the performance
of this unit when used with input tubes supplied by Quicksilver.
Quicksilver ships the Mid Mono Amplifiers with matched EL34 tubes but many different 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 controls are located between the output tubes near the power and output transformers
To adjust the bias you will need a slot-head screwdriver. Adjust by turning clockwise to increase
bias; counterclockwise to decrease bias.
Insert the black lead from the multimeter into the black pin jack on the amp. Insert the red lead into
one of the red jacks on the amp.The bias control that corresponds to offset of that jack is the one
used to adjust the bias of one tube. The millivolt reading on the meter is actually the bias current
in ma for one tube. Both tubes should be set to the same bias and 40 ma is a good starting point.
Larger tubes like the KT series of tubes can run higher bias and can be set where you feel the sound
is best.
Maximum bias is 50 ma for EL34s and 75 ma for the KT series tubes. The two bias controls do
interact somewhat so you may need to set the bias on each tube more than once. The closer in
bias the two tubes are set, the better the amp will sound.
WARNING
This device has very high internal voltages. Never operate with the bottom removed!
Never operate your amplifers with the speakers disconnected.
To prolong the life of your amplifiers, never turn them off and then on within a short period of time
(45 seconds.)
