CC Filament Power supply performance.

[santitrucco]

Hi, in Sakuma tube amps, there is a lot of examples of simples diodes + CLC or CRCRC (bigs C) CC filaments supply. Even in DHT tubes. Is this CC filament supply type a good performer?

 

[TR00]

There is better solution. https://www.diyaudio.com/community/threads/new-dht-heater.38248/

 

[schiirrn]

Even in DHT tubes. Is this CC filament supply type a good performer?

For indirectly heated tubes it's ok, for DHTs it's no good.

 

[Rod Coleman]

Is this CC filament supply type a good performer?

Constant Current? This is not a constant current supply. It's a passive DC voltage supply, and it is not constant either! The voltage will ride up and down with the mains voltage (as much as ±10%, not good for tube lifetime)

 

[santitrucco]

Constant Current? This is not a constant current supply. It's a passive DC voltage supply, and it is not constant either! The voltage will ride up and down with the mains voltage (as much as ±10%, not good for tube lifetime)

And with AC 100% variable voltage, the lifetime tube will be less than with +- 10% variable voltage ?

 

[schiirrn]

The RMS value of the unregulated dc supply will follow the RMS value of mains supply. ±10% mains RMS -> ±10% unregulated dc supply.

 

[astouffer]

Aren't most indirectly heated tubes rated for +/- 10% heater voltage and filament tubes rated +/- 5%?

 

[Rod Coleman]

> Aren't most indirectly heated tubes rated for +/- 10% heater voltage and filament tubes rated +/- 5%?

Yes, 5% in some cases, 10% in others. But such a wide range simply reflects the reality of mains supplies: the valves were being sold for use in mains-operated consumer equipment.

It does not mean that the lifetime is the same, anywhere from -10% to +10%.

This snippet from the Philips Technical review [1956 ed.] gives some guidance, and shows the benefit of never going above the nominal voltage.