Hi,
I´ve been tempted for a long time to build something quite similar to the TSE but with an adjustable B+ supply and some kind of modular design around the output tube sockets to allow the amp to use a wide range of different power tubes. To get the most out of it I would like to use the PowerDrive circuit but I'm a bit worried about how it behaves during startup. Is the delay/soft start from an IDH tube rectifier (I'm planning on using dual damper diodes) enough to avoid any nasty turn-on pulses into the grids of the output tubes?
Best regards,
Daniel
I´ve been tempted for a long time to build something quite similar to the TSE but with an adjustable B+ supply and some kind of modular design around the output tube sockets to allow the amp to use a wide range of different power tubes. To get the most out of it I would like to use the PowerDrive circuit but I'm a bit worried about how it behaves during startup. Is the delay/soft start from an IDH tube rectifier (I'm planning on using dual damper diodes) enough to avoid any nasty turn-on pulses into the grids of the output tubes?
Best regards,
Daniel
The startup of the PowerDrive circuit depends on the startup characteristics of the power supplies that operate the PowerDrive circuit. There are two common cases.
One is a vacuum tube rectifier for B+ and a solid state rectifier for the negative voltage source. This is how the TSE and TSE-II are set up. In this case the grid voltage on the output tube will be at or near the negative rail on power on, with a rise to the desired bias voltage as the rectifier in the positive voltage supply warms up.
Damper diodes for the B+ and solid state for the negative voltage supply are a good choice.
I have also used an isolation transformer like the Triad N-68X used to create a pair of supplies of about +/- 150 to 160 volts with solid state diodes. In this case the proper bias voltage will be available nearly instantaneously on power up.
It would be possible to use tube rectifiers for both supplies, but careful testing would be needed to avoid a faster supply for the positive source. This is also why a solid state rectifier for the positive supply and a tube rectifier for the negative supply should not be tried.
One should also be wary of large valued bypass caps on the bias pot or its voltage divider resistors for similar reasons.
One is a vacuum tube rectifier for B+ and a solid state rectifier for the negative voltage source. This is how the TSE and TSE-II are set up. In this case the grid voltage on the output tube will be at or near the negative rail on power on, with a rise to the desired bias voltage as the rectifier in the positive voltage supply warms up.
Damper diodes for the B+ and solid state for the negative voltage supply are a good choice.
I have also used an isolation transformer like the Triad N-68X used to create a pair of supplies of about +/- 150 to 160 volts with solid state diodes. In this case the proper bias voltage will be available nearly instantaneously on power up.
It would be possible to use tube rectifiers for both supplies, but careful testing would be needed to avoid a faster supply for the positive source. This is also why a solid state rectifier for the positive supply and a tube rectifier for the negative supply should not be tried.
One should also be wary of large valued bypass caps on the bias pot or its voltage divider resistors for similar reasons.
