Reply-To: Dr.Distortio--(at)--bs.mhv.net
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Tormod Eikill (teikil--(at)--elepost.no) wrote:
: I thought that the only tubes I could use on the output for my Twin was
: the 6L6 series. So when you're talking about "5881" or any other number, I
: don't understand shit. What is all this?
Between the varieties of 6L6 types available and the fact that certain
suppliers like to play fast and loose with the numbering system, it's
natural that a lot of confusion would result. Here's a very brief
overview of the 6L6 family of beam power tubes:
6L6: The original metal-cased version. Not recommended for most guitar amps.
6L6G, 6L6GB: The early glass versions. These are not rated for the kind of
service they would see in most modern guitar amps, although they are
found in some old amps from the '50s.
5881 (Old): This is a "ruggedized" military version of the 6L6GB. Again,
they're not rated for the kind of plate voltages and dissipation you see
in more modern amps, but they're great for old Fender Tweeds and the like.
Many folks (myself included) have used 5881s with no problems in
Blackface and Silverface amps, but they are being run beyond their
ratings in such cases.
6L6GC: This is the most modern version of the 6L6, and the one around
which all the '60s and later Fenders were designed. Ratings are higher
than the older versions.
7581, 6L6WGC, etc.: Ruggedized military 6L6GCs. A stock of Philips 7581s
has become available on the market recently, and the "word on the street"
is that they're very good tubes.
5881 (New): Sovtek/New Sensor and some other suppliers have seen fit to
revive the 5881 designation for their new 6L6GCs. These should not be
confused with the old 5881s--for instance, Tung-Sols. The Russian 5881s
are good reliable tubes, the best 6L6 type being manufactured right now.
They have been used succesfully in very tough applications, even as
quasi-substitutes for 7027s. In my opinion, this is the best tube to use
in just about all 6L6-based guitar amps.
One thing I should mention is that the new 5881 usually biases up at a
less-negative grid voltage than the other 6L6 types, so you cannot simply
plug a pair into your old Fender and get optimum results. The amp should
be rebiased by a competent tech.
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