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Power tubes as drivers -- Line Magnetic

I just purchased a LM 518 IA, which is a 22 watt SET integrated using 845 tubes. The amp uses 2 6L6 as drivers and 12ax7 for input.

I'm picking up the amp this week, and although I haven't seen the user manual yet, From what I can gather, virtually any power tetrode or pentode, including EL-34, KT-88, 6L6 and 6V6 can be used as a driver in this amp. Of course that means I'm getting ready to try a buncha tubes.

My current thought is to pick up decent, but not expensive, current production samples of the various tubes (probably all made by the same manufacturer to maintain some control) so I can get a handle on which sound I prefer most, then move on to more expensive and probably NOS versions of those tubes I like best. Just checking in with the community for reality check on if this makes sense to anyone else.

Also, I've seen on various tube sellers sites reference to "this (noisy/micro phonic) tube is only suitable for use in a driver stage . . . ." Can I infer from this that I can get away with slightly dodgy driver tubes and thus buy really fancy schmancy tubes in low grade and still achieve good results?

Will appreciate your thoughts.

D
dkidknow
dkidknow OP
60 posts
 
Chayro: Apparently, I absolutely am that guy! I've been enjoying the amp for a couple days now.

Tb: I'm driving Merlin TSM-MME. I also tried the 15W leben integrated, but it really didn't have the grunt to drive the Merlins. I'm not sure if it's the extra wattage or the current capability of the 845s, but the LM was a much better match for my speakers.

Ralph: I had never heard of class A2 until now. I just did a little reading-- very interesting. Until then, I would have had to use my best Nigel Tufnel accent to say class A2 is "one louder" than typical class A! Thanks for the info.
atmasphere's avatar
atmasphere
11,894 posts
 
We operate our amps in A2 mode as well. Fisher in the 1950s that made the first A2 amplifiers that I ever heard of.
dkidknow OP
60 posts
 
Ralph-- you might find it interesting that my Merlin TSMs, which are 8 ohm nominal and 6.5 minimum, are really enjoying being driven off the 16 ohm taps of the Line Magnetic. I'm getting a very open and extended sound but all of the bass definition I could want.
charles1dad's avatar
charles1dad
10,250 posts
 
Dkidknow,
Congratulations with the new amplifier. I get the impression that the Line
Magnetic 845 amplifiers are exceptionally good and possess excellent drive
capabilities. Based on owner reports like yours and also reviews, these LM
SETs are using high quality output transformers coupled with good power
supply design. As Ralph noted, the driver tube/ stage is robust.
I don't think Ralph would be surprised with your results using the 16 ohm
tap, you have to experiment with different speakers to find the best tap
usage. This amp offers much flexibility to tailor your sound with driver tube
choices. Also different brands of 845 offer additional fine tuning, there's
great potential with your amplifier. I believe that it's a true High End bargain.
Charles,
atmasphere's avatar
atmasphere
11,894 posts
 
Dkidknow, yes, the Merlins are an easy to drive speaker. I think that is the most popular speaker used with our M-60 amplifiers.
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