Just wondering the for tube amps is there a soft shut down circuit we can use it as reference.
i.e lets the amp slowly turn off, not to chop off the current to the tube arbitary and induce electromechnical stress inside the tube
PS yes soft shut down no soft start
i.e lets the amp slowly turn off, not to chop off the current to the tube arbitary and induce electromechnical stress inside the tube
PS yes soft shut down no soft start
A bit of classical after the drums and bass works wonders.
When when you instantly and completely remove power, the following happens:
The filaments quickly or slowly cool off, the cathode, if any quickly or slowly cools off, and the B+ quickly or slowly discharges until the tubes no longer conduct (and then the Bleeder resistor takes over for the discharging).
You do have a bleeder resistor, don't you? Prevent "The Surviving Spouse Syndrome"
The exact nature of all the above depends on the tube technology, DHT (filament only) or Indirectly Heated (filament and cathode), and the exact tube type.
There are directly heated output tubes, small signal tubes, and rectifier tubes.
There are indirectly heated output tubes, small signal tubes, and rectifier tubes.
There are solid state rectifiers (and inrush currents are the worry here, not shut down).
How many possibilities are there?
I do consider 'Hot Start Events' when I design an amplifier (the amplifier is warmed up and running, and then the power goes off briefly and then comes on again). Those events cause unusual transients, with some or all power tubes filaments and cathodes still warm, tube rectifiers still warm, or cold; etc.
I do not consider using soft shut down when I design an amplifier.
Instead, I sleep at night.
Now, to interrupt our sleep, have you considered what happens to the amplifier when the power mains voltage is at 65% to 85% of its normal voltage?
I still sleep.
Careful design allows us to sleep.
Over complex circuitry, and too much time spent worrying about certain potential problems causes lack of sleep.
If your tubes are dying before at least 2000 hours of operation, then look at the following items:
Power Mains Voltage variations from maximum to minimum. My mains go from 117V to 123V depending on time of day and the seasons of the year.
I am lucky to have such good power
Power Mains interruptions that cause hot start events
Quality of the tubes
Poor circuit designs that stresses the tubes, such as quiescent voltages, currents, and dissipation.
Another example: Too much resistance of the g1 resistor might cause thermal run-away, but might have some other limiting function that prevents it from just blowing up, instead causes the lifetime hours to be shortened.
Just my opinions.
The filaments quickly or slowly cool off, the cathode, if any quickly or slowly cools off, and the B+ quickly or slowly discharges until the tubes no longer conduct (and then the Bleeder resistor takes over for the discharging).
You do have a bleeder resistor, don't you? Prevent "The Surviving Spouse Syndrome"
The exact nature of all the above depends on the tube technology, DHT (filament only) or Indirectly Heated (filament and cathode), and the exact tube type.
There are directly heated output tubes, small signal tubes, and rectifier tubes.
There are indirectly heated output tubes, small signal tubes, and rectifier tubes.
There are solid state rectifiers (and inrush currents are the worry here, not shut down).
How many possibilities are there?
I do consider 'Hot Start Events' when I design an amplifier (the amplifier is warmed up and running, and then the power goes off briefly and then comes on again). Those events cause unusual transients, with some or all power tubes filaments and cathodes still warm, tube rectifiers still warm, or cold; etc.
I do not consider using soft shut down when I design an amplifier.
Instead, I sleep at night.
Now, to interrupt our sleep, have you considered what happens to the amplifier when the power mains voltage is at 65% to 85% of its normal voltage?
I still sleep.
Careful design allows us to sleep.
Over complex circuitry, and too much time spent worrying about certain potential problems causes lack of sleep.
If your tubes are dying before at least 2000 hours of operation, then look at the following items:
Power Mains Voltage variations from maximum to minimum. My mains go from 117V to 123V depending on time of day and the seasons of the year.
I am lucky to have such good power
Power Mains interruptions that cause hot start events
Quality of the tubes
Poor circuit designs that stresses the tubes, such as quiescent voltages, currents, and dissipation.
Another example: Too much resistance of the g1 resistor might cause thermal run-away, but might have some other limiting function that prevents it from just blowing up, instead causes the lifetime hours to be shortened.
Just my opinions.
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