Balanced Audio VK-55SE - Manual (Page 5)

Operating the VK-55SE
Normal operation of the VK-55SE requires simply turning the unit on. There are no
meters to connect, bias setpoints to remember, or drifting bias points to adjust. Please
read the Autobias Feature section for more details.
Turning the VK-55SE On:
The power switch is located at the front of the unit. As tubes warm up, their green LED
bias indicators will turn ON indicating their readiness. Different tubes can take different
times to get ready, but normally all four LED’s should be ON after about one minute.
Conditions such as low line voltage and tubes’ age can delay the readiness of the tubes.
Turning the VK-55SE Off:
The unit can be turned Off at any time (even while playing). If needed, please wait at
least 30 seconds before turning the unit ON again.
Autobias Feature:
The VK-55SE implements a sophisticated autobias circuit that automatically
compensates for tube aging and line voltage fluctuations, as well as marginal
mismatching of tubes. The successful operation of the autobias circuit is noted by
individual LED’s that glow visibly next to each output tube when viewed from the top of
the chassis. A total of four LED’s should light up to indicate proper operation of the
circuit. If one of the LED’s fails to light up (after the unit is warm),
there could be two
reasons for this problem:
1. The particular output tube is defective. In this case replacing this tube with a
known good one should turn the LED ON.
2. The amplifier was overstressed and the protective fuse inside opened. These
fuses protect output tubes from overloading. There are two fuses accesible
through the top of the unit. Please refer to the section on replacing fuses for
correct ratings.