How to Adjust a Luxman Amplifier Transistor Bias
Luxman produces high-end home audio amplifiers. Usually valve powered, these devices use a set of vacuum tubes to balance voltages between the different power stages of the amplifier. Tube amplifiers produce warm, organic tones, but they need to be properly balanced in order to protect the equipment and produce the best sound. Adjusting the bias determines the ratio of voltage load between the tubes.
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Instructions
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1
Disconnect the amplifier from the power supply and press the main power button or switch on and off three or four times. This will ensure that any residual charge is drained from the amplifier's capacitors, reducing the chance of electrical shock.
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2
Unfasten the screws that hold on the vacuum tube grille cover. It's not necessary to have the cover removed to adjust the bias, but it will allow you to see if any of the tubes are blown or malfunctioning, which could give you a false reading from the bias dial on the main control panel.
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3
Reconnect the amplifier to the power supply and switch it on.
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4
Press the "V1" button in the "Meter SW" section on the control panel. This will target the bias meter to the first valve. Check the bias meter for its readout; the needle should be resting in the blue "OK" section on the readout. If not, use the screwdriver to turn the "Bias" screw underneath the "V1" button until the needle rests in the blue section.
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5
Press the "V1" button again to deselect the first valve, then press the "V2" button to highlight the second power valve. Adjust the bias using the screw, in the same manner as with the first valve.
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Tips & Warnings
To ensure the most accurate results, it is best to do this test and adjustment immediately after installing new valves, but adjustments can be carried out at any time by using the screws on the panel.
References
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