
AC Input: 120V/60Hz (USA) or 235V/50Hz (Europe).
The IEC AC powerinput socket connection is located at the far left in the back. A main
fuse is located inside under IEC socket. One Computer grade main cables (Detachable) is
included with the 300B tube amplifier. If you choose to replace the AC main cable with an
esoteric type, make sure that is has a third pin for grounding the unit.
ON/OFF Switch: Left Side Panel control: On/Off push button power switch.
Source Selector: 1 –2 –3 –4 - 5 - mute
Using Sophia Electric 91-03 300B Stereo tube amplifier
1) Allow the unit about 15-20 minutes to warm up before doing any serious listening. This
will allow the circuit to stabilize and components to settle.
2) Avoid repeatedly turning the unit on and off in quick succession. This may damage the
tubes and some of the power supply capacitors quickly.
3) Never disconnect the output wires while your amplifier is turned on (damages to the
single ended output transformer may happen).
4) Caution: Do not touch the speaker binding post once the amplifier is on or within 2
minutes after it is turned off.
5) Do not keep the amplifier on around the clock overnight. Capacitors and tubes have
finite lifespan. Recommend to take a short break every 5 hours to let the amplifier cool
down to the room temperature before your next session.
6) Do not do silly things with a vacuum tube amplifier, such as take amplifier for car wash.
Do not use dish washer to clean tubes.
Sophia Electric amplifiers have been designed with quite operation in mind. All
new amplifiers shipped from Sophia Electric have been adjusted to factory
specification for quietness.
At times when users are in need for hum control adjustment, please follow the
following steps.
Hum Control Adjustment Procedure:
1. The main hum control pots on the top next to the 300B tube sockets are for the
300B tubes. User can adjust these main hum control pots to achieve min
hum/noise when changing to another 300B tube.
2. The second pair of hum control pots in the front row next to 6SN7 tubes is for
6SN7 driver tubes. User can adjust the pots to achieve min hum/noise when
changing to another 6SN7 tube.
3. User can use multi-meter AC function or scope to monitor the hum level.