Need help with 6E5P UL bias point.

[Tjj226]

Hello everyone. I hope everyone is still doing well during these times.

I have a couple edcor 7.6K UL push pull transformers that I would like to turn into a small amplifier.

I am looking at using a single stage 6E5P push pull amplifier and I would like to give UL a shot with these tubes to see what sort of power I can pull out.

The problem is that I can't find any UL curves for this tube, so I can't figure out what the bias point should be.

If any of you could point me in the right direction, or if you guys think UL with this tube might be a waste of time, please let me know.

 

[TG]

Since the plate and the second grid are more or less at the same voltage in the UL mode, you can use triode curves for determining the operating point.
Dynamic curves will be different, of course.

 

[GoatGuy]

According the the Frank's PocNet datasheet, you want about –1.7 V of G₁ bias, by however means your design merits. This results in anywhere from 35 to 50 mA nominal with a V_A (relative to V_K) of 125 to 175 V.

But what do I know?
Russian valve data is notoriously … hmmm … challenging to interpret.

⋅-=≡ GoatGuy ✓ ≡=-⋅

 

[Tjj226]

According the the Frank's PocNet datasheet, you want about –1.7 V of G₁ bias, by however means your design merits. This results in anywhere from 35 to 50 mA nominal with a V_A (relative to V_K) of 125 to 175 V.

But what do I know?
Russian valve data is notoriously … hmmm … challenging to interpret.

⋅-=≡ GoatGuy ✓ ≡=-⋅

Yeup. I honestly don't enjoy working with russian tubes for that very reason.

But they are cheap and have interesting specs so I guess I shouldn't complain.

If that is the case, I will shoot for ~175 at 45ma.

Lets just hope the damping factor will be high enough so that I don't have to use global feedback.

 

[Mother of PEARL]

All the 6E5P data you might ever want is right here https://www.pearl-hifi.com/06_Lit_Archive/08_Tube_Data/Cons_Data/6E5P_Cons_Data.pdf so just haul off and the build the thing. Tapped primary UL isn't optimal but you'll get 2-3 times the power at <half the distortion.