Biasing
Your Essential is configured in Fixed-Bias and the bias must be checked / adjusted when changing
output tubes. If you are unfamiliar with this procedure please consult a qualified amp technician.
Biasing Procedure
1) Ensure the amplifier is connected to the speaker before applying power.
2) Connect your multimeter - black probe to black test point and red probe to the red test point.
3) Turn your multimeter to the Volts setting, millivolts if available.
4) Apply power and allow tubes to warm-up.
5) Using a flat head screwdriver adjust the bias pot (underneath chassis) until the meter reads the
desired setting.
Settings between 42 and 48mV (0.042 to 0.048V) are appropriate with the factory setting being
45mV.
Important! Do not exceed this range as it can lead to tube failure or failure within the amplifier.
Using 2 Speaker Cabinets
While one speaker is certainly su$cient to get the most out of your Essential there are times when
you may wish to add a second speaker cabinet.
Key concepts:
-Both cabinets must be the SAME impedance, eg 8 ohms.
-Combining impedances in parallel results in an overall impedance of HALF the original
impedances.
-Ensure the correct impedance is selected on the IMPEDANCE SWITCH.
Example 1: 8 ohm cab + 8 ohm cab in parallel = 4 ohm overall impedance. Therefore select the 4
ohm setting on the Impedance switch.
Example 2: 16 ohm cab + 16 ohm cab = 8 ohm overall impedance. Therefore select the 8 ohm
setting on the Impedance switch.
