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6L6 v. 5881 - what difference to expect?


Suhr S-Classic, V60LP's, Soft V neck
Gold Supporting Member
The subject line pretty much sums it up - what should I expect in tonal difference and performance between a set (2) of 6L6 and a set of 5881's - I'm thinking about putting some 5881's in a Rambler (orig. Kingpin 12") mostly because the amp wont have to be re-biased to try this, so it's an easy thing to do - I really don't know what to expect - so I'm askin' - thanks in advance for the info.


They're the same tube. The "5881" is a European designation.

You have to rebias everytime you change power tubes.
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If you're switching from a 6l6GC to a 5881 be sure to watch your plate voltages. A 6l6gc is a 30 watt tube rated for 500 Volts, while the 5881 is 25 watts and usually designed for a max of 400 Volts. Some people just shorten 6l6GC to 6l6 not realizing that they're different tubes. However if it really is a 6l6 just ignore me.


Gold Supporting Member
Copied from the Rambler manual:
"The Rambler is a cathode bias (self bias) amp and as such does not require a bias adjustment when changing tubes. Please use well-matched pairs of output tubes for maximum performance and minimum hum in Triode mode. The Rambler can only use matched pairs of 6L6, 5881, or 7581A power tubes."

A PDF of the manual is at this link:

As for the original question, I swapped in some 5881's for the original 6L6's in a Carr Vincent (now known as the Viceroy) and got earlier breakup and what I would call a rounder, more dimensional tone. YMMV.


Platinum Supporting Member
You should re-bias with any power tube change... even 6L6s to 6L6s... different brands and even different tubes within the same brand should ALWAYS have the bias checked upon swapouts.

as has been indicated above, 5881s are NOT the same tube... earlier breakup, smoother breakup, better midrange frequency emphasis, etc...



as has been indicated above, 5881s are NOT the same tube... earlier breakup, smoother breakup, better midrange frequency emphasis, etc...
To me (in a Mark IV and a Fender Twin) the 5881's midrange emphasis always felt like a "hard" upper mid that did not sit well in my ear.

I am pretty sure both times were Sovtecs so take that for what it's worth. I am very sure I switched back to 6L6 GC's.


When I bought my JTM45 reissue I had 2 to choose from- one with 5881s, the other with 6L6s. They sounded different from one another, and I chose the latter.

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