Groove Tubes GT-6L6-R similar to 5881 25 watts?

[TomCarlos]

MEF:

I am working on an amp that has a pair of Groove Tubes GT-6l6-R installed. I found an old thread (actually there are a few threads) that address this tube. But it wasn't clear as to what these tubes are similar to. My best guess was to treat them like a 5881, 25 watts.

Here is the thread I found - Ampeg Rocket Reverb 2X12

I also found a Groove Tube Reference Guide from 2012. Sure enough, right there, it shows this as a 5881 equivalent.

So I will use the Robinette Tube Bias Calculator for the recommended bias setting.

Unless there are any differing opinions, this is just an fyi for weekend warrior techies like me!

[pdf64]

The design centre anode limit of 5881 is 23W https://tubedata.altanatubes.com.br/...049/5/5881.pdf
https://www.jj-electronic.com/en/5881
Using a typical coefficient, an equivalent design max limit would probably be about 26 -27W.
A weird thing is that 6L6WGB, which are supposedly the same valve as the 5881, have an absolute max anode limit of 26W https://tubedata.altanatubes.com.br/...7/6/6L6WGB.pdf
Usually, absolute max ratings are about 20% higher than design max. Perhaps the difference can be minimal if valve variance to type nominal is very low?

[vintagekiki]

Groove Tubes GT-6L6-R is Russian Power Tubes

6L6GC Comparison of Current Made Tubes
https://www.amplifiedparts.com/tech-articles/6l6gc-comparison-current-made-tubes

6l6gc Comparison of Current Made Tubes
https://www.scribd.com/document/241089889/6l6gc-Comparison-of-Current-Made-Tubes-1

Sovtek 5881 WXT
https://www.scribd.com/document/114373154/Sovtek-5881-WXT

GT-6L6-R Power Tube datasheet request
https://music-electronics-forum.com/forum/amplification/guitar-amps/theory-design/42363-gt-6l6-r-power-tube-datasheet-request

Tube datasheets ¹⁾
https://drtube.com/en/library/tube-datasheets

[Enzo]

Tom, consider that in audio the difference between 23 watts and 30 watts will be almost inaudible. When biasing up a 6L6 considered a 30 watt tube, what would hgappen if you biased it up as if it were a 25 watt tube? Not much difference.

[TomCarlos]

Thank you Enxo, VK, and PDF. Yes, there isn't much of a difference.

These tubes happen to be in a Yamaha T50C combo amp, designed for 6L6GC tubes. So perhaps my friend dropped these into the amp because it is a spare set he had on hand.