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Vacuum Tubes for Amps
What is 5881
After participating in several discussions re 5881/6L6-WGB here,
I did a little rummaging through my reference material and came up
with the following items:
RCA RC-23: Lists max plate voltage (design center) at 400V,
Pa at 23 watts, but then refers the reader to 6L6-GB for typical data.
Sylvania: Lists 23 watts max Pa, 360V max Va, but then gives data
for using them as ultralinear PP cathode-bias amp with 450V.
GE:Reiterates 6L66-GB data, same Pa max 23W, Va max 360V.
World Vacuum Tube Technical Manual: Lists same Pa max and Va max
as GE & Sylvania, but then gives data for using them in triode
at 400V.
Now IMHO, the differences between 5881 and 6L6-G/GA/GB were
likely marketing and different interpretations of how tube ratings
should be arrived at. As far as being a truly substantial difference,
as far as enduser were concerned, for practical purposes there
would have been little or none at all.
Same goes for 1614...I've seen a number of RCA 1614's that had
"6L6" stamped in the metal. Apparently even RCA didn't consider
the differences between 6L6 and 1614 to be worth worrying about.
The reasons I say this, is because (a) there were amplifier designs
almost dating back to the 6L6's introduction in 1936, that put over
400V on them (b) RCA sold "6L6-GC" tubes that appeared not to
have the special plate (anode) material that the GE 6L6-GC had.
Essentially, they were 6L6-GB's. Changing a label does
not, of course, change the internal parts, and shouldn't change the
ratings, either. But they were issued as 6L6-GC with the
purchasers assuming that they had 6L6-GC ratings.
Even stranger, RCA also issued the original 7027
about the same time, which had ratings of 450V Va max
and 25W Pa max. And internally they sure look a
lot like a 6L6-GB...Golly, they test about the same, too.
(note I'm not talking about 7027A, which was re-rated
using the design-maximum system)
In effect, RCA was saying that you *could* have run the old
6L6/G/GA/GB at much higher Pa and Va than the ratings RCA
originally issued for those tubes...!
The first 6L6 version with a substantial difference in construction
and ratings was the 6L6-GC, introduced by GE in 1961.
These used a new type of 5-ply composite anode (plate)
material that substantially improved heat dissipation
capacity. GE rated them at 30W Pa, 500V Va max.
To throw a monkey wrench in the whole tube ratings game,
tube manufacturers issued 6L6-WGB and 5881 later, which
apparently used the same 5-ply plate material as a 6L6-GC.
Thus you really just have a 6L6-GC with a smaller bulb.
Then there's Russian 5881, which aren't quite the same
as the late model US ones, and seem to get their "5881"
moniker mainly due to having a similar bulb size as the
US 5881....
Ned Carlson
Triode Electronics
2225 w. Roscoe St
Chicago, IL 60618 USA
email: triodee--(at)--nterserv.com
ph:773-871-7459
fax:773-871-7938
"Worldwide service,
Neighborhood prices"
since 1985
From triodee--(at)--nterserv.com Fri May 23 11:35:39 CDT 1997
Article: 31273 of rec.audio.tubes
From: triodee--(at)--nterserv.com (Ned Carlson)
Newsgroups: rec.audio.tubes
Subject: Re: So what IS a 5881, anyway???
Date: Fri, 23 May 1997 09:55:05 GMT
Organization: Triode Electronics
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triodee--(at)--nterserv.com (Ned Carlson) wrote:
>After participating in several discussions re 5881/6L6-WGB here,
>I did a little rummaging through my reference material and came up
>with the following items:
>
>RCA RC-23: Lists max plate voltage (design center) at 400V,
>Pa at 23 watts, but then refers the reader to 6L6-GB for typical data.
>
>Sylvania: Lists 23 watts max Pa, 360V max Va, but then gives data
>for using them as ultralinear PP cathode-bias amp with 450V.
>
>GE:Reiterates 6L66-GB data, same Pa max 23W, Va max 360V.
>
>World Vacuum Tube Technical Manual: Lists same Pa max and Va max
>as GE & Sylvania, but then gives data for using them in triode
>at 400V.
And here's another spanner to toss in the gears of this debate:
ARRL Raidio Amatuer's Handbook 1951 gives
ratings for 6L6/6L6-G
as Pa max = 21 watts, Va max 400V.
And 6L6-GX (GX is ceramic-base version)
with Va max 500V.
These *may* be ICAS ratings, but book does not
say that.
There were also some other odd 6L6 variants...T-21, RK49, and
HY-6L6-GTX, as well.
Then there's 807 (a spinoff of 6L6-G, but with diifferent screen
voltage ratings), plate looks about the same size as 6L6,
GE gives it 25W absolute-maximum rating, ARRL
(this again may be ICAS, though) gives it 30 watts.
Ned Carlson
Triode Electronics
2225 w. Roscoe St
Chicago, IL 60618 USA
email: triodee--(at)--nterserv.com
ph:773-871-7459
fax:773-871-7938
"Worldwide service,
Neighborhood prices"
since 1985
From le--(at)--euron.uchc.edu Fri May 23 11:36:00 CDT 1997
Article: 31281 of rec.audio.tubes
From: Les Bernstein
Newsgroups: rec.audio.tubes
Subject: Re: So what IS a 5881, anyway???
Date: Fri, 23 May 1997 08:58:02 -0400
Organization: Univ of CT Health Center
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Xref: geraldo.cc.utexas.edu rec.audio.tubes:31281
Ned Carlson wrote:
> The first 6L6 version with a substantial difference in construction
> and ratings was the 6L6-GC, introduced by GE in 1961.
> These used a new type of 5-ply composite anode (plate)
> material that substantially improved heat dissipation
> capacity. GE rated them at 30W Pa, 500V Va max.
Actually, the 6L6GC was introduced in 1959.
>
> To throw a monkey wrench in the whole tube ratings game,
> tube manufacturers issued 6L6-WGB and 5881 later
The 5881 and 6L6WGB were not issued later, but quite a bit BEFORE the
6L6GC. The Tung-Sol 5881 dates back to 1951-52 and has ratings between
a 6L6GB and a 6L6GC. Note that the 6L6WGB is virtually identical to the
5881 differing in the type of spacers used. That is, a 6L6WGB is NOT
the same as a 6L6GB.
Otherwise, thanks Ned for the detailed history. I suggest those who are
interested in the history of the 6L6 series grab a copy of Eric
Barbour's "6L6 Forever 1936-96 60 Years of Amplifier Service" in VTV #4.
Les
From triodee--(at)--ol.com Fri May 23 20:53:59 CDT 1997
Article: 31306 of rec.audio.tubes
From: triodee--(at)--ol.com (TRIODE EL)
Newsgroups: rec.audio.tubes
Subject: Re: So what IS a 5881, anyway???
Date: 23 May 1997 22:20:23 GMT
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>Actually, the 6L6GC was introduced in 1959.
My GE paper says 1961, maybe GE didn't introduce
their version til then.
Or they typoed the date (certainly not impossible!) !!
> To throw a monkey wrench in the whole tube ratings game,
> tube manufacturers issued 6L6-WGB and 5881 later
>The 5881 and 6L6WGB were not issued later, but quite a bit BEFORE the
They were INTRODUCED earlier, but later the factories
ISSUED new versions using different than original materials etc.
Sorry for the misunderstanding.
The 5881 shows up in my 1951 Tungsol Tube Guide.
Oddly, no additional voltage rating is claimed for it
(as opposed to 6L6-G).
Ned, Triode Electronics, Chicago
micK pages
