Regarding protection of tube circuits and tubes, PrimaLuna integrated amps come with "bad tube indicator" circuits: when a power tube starts to fail, the BTI puts the amp in safe mode and a red LED lets you know which tube is the culprit. I think it's a great feature - it has saved my bacon a few times in the 8 years or so I've owned my PrimaLuna.
Tube amplifiers - software recalibration?
Do tube amplifiers need calibration adjustments periodically? Absent being properly calibrated can this cause amps to be shut down due to existing voltage monitoring controls designed to protect the tubes?
What types of controls exist to protect tube circuitry and tubes? I've heard McIntosh has power guard features, but I thought this extended to protect the speakers. Is this a good thing or does it impairs sonic quality?
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@emergingsoul Some amps need adjustment and others do not depending entirely on design. Amps that do not need adjustment have a substantial cathode resistor whose value is chosen to set the tube's operating point once the tube starts conducting and creates a voltage drop across the resistor. This is known as cathode bias. The other form of bias is known as 'fixed bias'. This is where the bias is controlled by a voltage imposed on the grid of the tube, by a manual or automatic adjustment. If a manual adjustment, there may be a meter supplied on the amp or a provision to test the tube's setting in some manner using an external Voltmeter or Ammeter. If the bias is automatic, there may still be an indicator to show the tube's state. It might simply be an LED. But there would be no adjustment to tinker with. If in doubt, read the manual or contact the dealer/manufacturer. |