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06-26-2023, 11:22 PM
Hi Guys
Note that diode bias for gain stages is highly restrictive and could be thought of as a form of fixed-bias that is nonadjustable. As TUT described, diode bias also blocks the option for voicing via the cathode.
TUT describes the use of power tubes as preamp gain stages. It is generally low on return for investment, shall we say, but if it provides the character you desire then just do it. The iteration shown here may have a conflict between the fixed cathode potential and the variable screen potential, assuming the pot will be on the panel rather than used as a preset. If it is to be a user control, it would be better to have conventional cathode biasing.
The inductive load will allow for a high output, but power tubes do not have that much voltage gain per se. They are also noisier than preamp tubes. The heater current is quite the penalty, as well. On the other hand, you can drive fairly low load resistances since there is far more cathode current available than any preamp tube could offer.
Note that diode bias for gain stages is highly restrictive and could be thought of as a form of fixed-bias that is nonadjustable. As TUT described, diode bias also blocks the option for voicing via the cathode.
TUT describes the use of power tubes as preamp gain stages. It is generally low on return for investment, shall we say, but if it provides the character you desire then just do it. The iteration shown here may have a conflict between the fixed cathode potential and the variable screen potential, assuming the pot will be on the panel rather than used as a preset. If it is to be a user control, it would be better to have conventional cathode biasing.
The inductive load will allow for a high output, but power tubes do not have that much voltage gain per se. They are also noisier than preamp tubes. The heater current is quite the penalty, as well. On the other hand, you can drive fairly low load resistances since there is far more cathode current available than any preamp tube could offer.
