Can someone explain DHTs to me?

[bobopedic]

Hi, I'm trying to understand the relation between the cathode and the heater on a DHT. They are supposed to be one in the same yet the heater on the 300b for example has a 5v heater supply rating yet people claim to use much higher voltages on the cathode.

I want to create a white cathode follower circuit using DHTs but I don't even know if it's possible?
I've read that DHT cathode followers can be made but how can a DHT be a cathode follower if the heater and cathode are one in the same?

 

[Paul Birkeland]

Hi, I'm trying to understand the relation between the cathode and the heater on a DHT. They are supposed to be one in the same

They are.  When you look inside a big DHT like a 300B, you'll see the (usually) sold metal plate, some rods with a spiral of wire wrapped around them that are the grid, then a "W" shape of wire hanging inside the grid that's the filament. 

yet the heater on the 300b for example has a 5v heater supply rating yet people claim to use much higher voltages on the cathode.

5V is required between pins 1 and 4 for the tube to attain proper emission.  If both pins 1 and 4 are elevated that is biasing, which is entirely separate.

I want to create a white cathode follower circuit using DHTs but I don't even know if it's possible?
I've read that DHT cathode followers can be made but how can a DHT be a cathode follower if the heater and cathode are one in the same?

This can be done, but I wouldn't recommend it.  You would need several floating DC supplies to heat whatever DHT you decide to use to accomplish this, and the cost and complication of the project will get pretty high. 

 

[bobopedic]

Lets say in theory I did make this DHT WCF. Would it sound better than an IDHT using 6as7/6080 tubes? DHTs have far better linearity right?

 

[Paul Joppa]

There is only one way to know, and that is to try it and listen.  :^)

If you do, the main thing to know is that each filament/cathode must have its own power supply, free to float away from ground.