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06-05-2023, 06:13 PM
Hi Champ81
Tube data sheets should indicate the limiting values, but not every sheet does especially ones produced for tubes recently. Semiconductor data sheets ALWAYS include limiting values.
Tube data sheets generally show a few applications, which in themselves, do not tell you the limitations of the device. You have to remember that the "limit" is exactly that - the value that should not be exceeded. However, every value below that is okay and safe given that the device is kept within its dissipation (heat) limits.
Tube data sheets are also confusing inasmuch as the protocol used by the manufacturers changed in the mid-1950s BUT not all data was updated. Modern manufacturers still parrot the obsolete protocol, which makes their products look very poor indeed. The old protocol included tolerances for the manufacturer's own deviation of production PLUS anticipated sloppiness of equipment design where the tube would go.
Your amp was designed to provide a specific maximum audio output power. The PT and OT work together to make that power available. The amp designer decided to make the amp cathode-biased. You can change it to fixed-bias but you will not get more power than the PT-OT allow. Similarly, installing higher-power rated tubes will not get more power in this circuit.
TUTs explain how amps are designed. what mods can be made, what is safe to do with tubes. Other references, such as RDH Radiotron Designer's Handbook, follow more restrictive rules but also explains everything. The presentation may be beyond your skill at the moment, where TUTs make things a bit easier to understand and are on-point regarding MI application.
Tube data sheets should indicate the limiting values, but not every sheet does especially ones produced for tubes recently. Semiconductor data sheets ALWAYS include limiting values.
Tube data sheets generally show a few applications, which in themselves, do not tell you the limitations of the device. You have to remember that the "limit" is exactly that - the value that should not be exceeded. However, every value below that is okay and safe given that the device is kept within its dissipation (heat) limits.
Tube data sheets are also confusing inasmuch as the protocol used by the manufacturers changed in the mid-1950s BUT not all data was updated. Modern manufacturers still parrot the obsolete protocol, which makes their products look very poor indeed. The old protocol included tolerances for the manufacturer's own deviation of production PLUS anticipated sloppiness of equipment design where the tube would go.
Your amp was designed to provide a specific maximum audio output power. The PT and OT work together to make that power available. The amp designer decided to make the amp cathode-biased. You can change it to fixed-bias but you will not get more power than the PT-OT allow. Similarly, installing higher-power rated tubes will not get more power in this circuit.
TUTs explain how amps are designed. what mods can be made, what is safe to do with tubes. Other references, such as RDH Radiotron Designer's Handbook, follow more restrictive rules but also explains everything. The presentation may be beyond your skill at the moment, where TUTs make things a bit easier to understand and are on-point regarding MI application.
