THF-51S biasing recommendations

[jolintsai]

Hi guys,

I'm going to build a class A amp using THF-51S SIT since I can only find this instead of 2SK82, 2SK180 or 2SK182. THF-51S should behave similarly since they're the same class of device - SIT.

The final design is probably gonna look like this below but I have to experiment with the bias first before reaching the end point since OPT is going to be tailor made to the bias / standing current of final THF-51S bias point.

If anyone has tried THF-51S SIT with choke, CCS or even bulb loading, please share what the recommended bias is (load resistance, DC current, B+ voltage, and etc).

Thanks a bunch!

 

[Pascal Nguyen]

THF-51S amp working condition in my notes (within sit’s SOA)
... maybe my sit has different spec than yours...

Cheers

 

[jolintsai]

Thanks very much, MossFed.

Looks like the higher the voltage, the lower the distortion!

 

[Blitz]

Well...if mu starts to become constant from 280 V up, no wonder that the distortion goes down the higher Vgs becomes, no ?

Did you try something over 300V ?