Hi there.
First of all apologies for writing in English. Hopefully it won't cause too many problems.

I am trying to learn more about tubes and I was wondering if someone can explain all the values printed on the tube-town valve boxes. I know some of them but some are not clear for me.
I have a Sovtek 5881 tube with the following data:
P: 450v G:400v G1: -37v

Are these the values used to test the  tube ?
So tests performed with plate at 450, screen 400 and grid -37 ?

I then see:
Gm: 4,4
Ip: 56

Those are fine as I know what they are (plate current and transconductance)

But what are these measurements :
H2C: 0
S: 1,9
G: 0,6
G1: 0,037

Many thanks in advance for any info.

Danke
Paul

Zitat von: Luxpaul am Okt 01, 2026, 12:53
P: 450v G:400v G1: -37v

Are these the values used to test the  tube ?
So tests performed with plate at 450, screen 400 and grid -37 ?

Yes, these would be the parameters the tube was tested at. Every other value is dependent on those parameters, so you could only compare tubes based on the given values tested at the same parameters.

Zitat von: Luxpaul am Okt 01, 2026, 12:53
But what are these measurements :
H2C: 0
S: 1,9
G: 0,6
G1: 0,037

H2C = Heater to Cathode ("overspeak" from the heater to the cathode)
S = Steilheit. I don't know the english term for that (is it "slope"?), but it describes the steepness of the characteristic curve of the tube in mA/V. So the change of plate current per volts change at the Grid (G1).

I have no idea about the G and G1 values (grid current maybe, but without information about the unit for the values hard to tell).

Maybe this helps:
https://media.tubetown.net/cms/?Know-How/Tube_Matching_and_Selection

Great.
Thanks a lot  :topjob:

The english term for S (Steilheit) is transconductance (gm).

I think "G" should mean screen grid (G2).

I would have hoped for Dirk to clarify.

No problem, it certainly makes sense.
Thanks again