Understanding bias setting TSE

[waltroman]

Amps is back up and running after C6 bit the dust and in setting everything up I pulled the meters out and spent some time making sure all is set and stable.

I have a few different 5U4G rectifiers and I noticed that the Raytheon has lower B+ voltage the the two RCA's, 248-250 vs. 282-286. In deciding to leave the lower volt rectifier in there I spent some time getting the bias set where it sounded the best. 32mA was the ticket.

If I decide to run one of the higher voltage rectifiers should I reduce bias? Hot hot is too hot? What about tube life?

I believe I understand the principal of bias just looking for the practical. I also have read Georges suggestion of where to bias a 45 amp in Tubes and Applications.

Why does suggested bias go down at higher voltages?

Thanks,
Walt

 

[zxx222]

Voltage x current = plate dissipation power. Max value is in datasheet, it is not recommended to exceed it.

 

[gcom]

You may have read this already but I think it explains well how the tube dissipation and voltage don't always go up in line with each other.

Idle Current Biasing - Why 70 percent?

I can't say that I can follow it all but I am picking up bits and pieces of it.
I am just starting a SSE build so I'm trying to learn myself.

 

[waltroman]

Good article GCOM but I believe the TSE is a class A amp tubelab recommends to run the tubes bias 28-30 mA where data sheets indicate 34mA as the top. I get that running the tube 'hot' may decrease life but is this the reason for the lowered recommended bias.

 

[hewo]

cold vs hot

heaters determine the activity of the moment, & over time their perform does lessen, so, every aspect, to emphasize their longevity has been incorporated, e.g., thorium filament coat, dc drive, possibly boost plate tension