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11. Master Volume II. See Master Volume I (item 10) above
12. 'On' Light. This red jewel light illuminates when the unit is supplied with the correct mains voltage and
switched on. When switched off, the light will slowly extinguish.
13. Standby. When switched to 'On' the amp is active and can be used. When switched to off, the valve
heaters are on, but the signal path is inactive. This should be switched to 'Off' when the amp is first
turned on, and switched to 'On' after the valves have warmed up (approximately 1 minute). This will
help prolong the life of your valves.
14. Main Power Switch. Turning this 'Off' disconnects the amplifier circuit from the mains voltage.
Rear Panel Layout
1. IEC Input socket. Connect the supplied mains lead here. The mains fuse is also located below this
socket. Replace the fuse only with the same type and rating stated on the rear panel. If a replacement
fuse fails immediately, contact your local service agent. DO NOT replace with a higher value.
2. HT Fuse
3. Bias Adjust and Test Points. These enable a competent engineer to easily adjust the bias for the power
valves. Connecting a meter between TP1 and TP0 allows the bias voltage to be measured for valve 1,
and between TP0 and TP2 allows the bias voltage to be measured for valve 2. Contact the Carlsbro
service dept for detailed instructions on biasing of valves
Note: We recommend that a qualified electronic technician, using suitable test equipment, performs installation
of valves and valve biasing. Incorrect adjustment of valve bias can shorten valve life, degrade tone and
performance and lead to amplifier damage.
4. Triode/Pentode ('half power') switch. This selects the mode the power valves operate in. Pentode
mode will give the full 50W output, whilst Triode mode will give 25W output, with a slightly different
tone.
5. Speaker Outputs. This amp has 3 speaker outputs: one for a 16 ohm load (i.e. one 16 ohm cabinet),
and two for an 8 ohm load (i.e. one 8 ohm or two 16 ohm cabinets). DO NOT combine the 8 and 16
ohm output sections. Make sure you use the correct impedance load.
6. Footswitch sockets. Connect any suitable 2 way footswitch with a stereo jack lead to socket 1 to switch
channels and master volumes, or to socket 2 to switch boost and effects loop on/off. These sockets
can be connected to two separate 2-way switches, or the Carlsbro 4-way footswitch (AC1182). Note:
the front panel switches for channel and boost must be 'in' for the footswitch to operate.
7. Series/Parallel Switch. This selects whether the effects loop works in parallel with the amp signal chain
(i.e. final output is a mix of 'dry' direct and 'wet' effected signal) or in series (i.e. all signal passes
through the effects, and final output is all 'wet' effected signal.
8. Send & Return Sockets (FX Loop). Use these to connect external effects units, or to send the preamps
output to another amp. Note that this loop is inactive and not connected to the signal path until a jack
plug is inserted into the return socket.
NOTE: ALWAYS DISCONNECT THE UNIT FROM THE MAINS BEFORE REPLACING THE FUSE.
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