300B Filament Voltage Range

[dsavitsk]

Is it safe to run 300B's with a filament voltage of 5.23V, or is this too high?

If it is too high, does anyone have a suggestion on how to drop the voltage by a very small amount? The current draw of these particular tubes seems to be about 1.2125A necessitating either a ~ 0.19R resistor or some other means. Is a Mills 0.18R the best option?

 

[Bas Horneman]

5,23 is acceptable...but indeed dropping the voltage with a small resistors would be the best option I think..Some report slightly better sonics with just below <5V voltages.

 

[kmtang]

5.23V is within safe range for 300B's filament. However, it is good to add a small dropping resistor which would cut down the start up current.


Johnny

 

[dsavitsk]

The filament voltages were at 4.26V with a 0.8R dropping resistor. Jumpering over the resistor raised them to 5.22. Interestingly, I think the amps sounded considerably better with 4.26V. They seem to have become less lush (a little sterile sounding) as well as a bit sluggish at the higher voltage. As soon as I can get my hands on some different resistors, I am going to try for a bit under 5.

-d

 

[Sheldon]

If you can give up a little output you don't need to rule out the possibility of running at 4.26V.

http://members.aol.com/sbench102/dht.html

Sheldon