2. amps-preamps
  3. 1160515217

Tubeaholics please advise

I have the Counterpoint SA-4 OTL monoblock amps, which I bought retubed about 10 years ago, running Martin Logan CLS's. No problems so far, but the mileage is getting up there. You cannot bias the SA-4 tubes individually, so matched sets of tubes are recommended. They take 8 6LF6's per side, which I am now finding out are nearly impossible to find NOS in any quantity, and if you can find them, are going $100.+ per tube!
Issue: (1) should I buy a few used tubes and keep nursing the amps along, despite the fact the used tubes will not be matched? Or just start saving now for a new set of amps? (2) given that OTL amps can fry speakers when the tubes die, what are the telltale signs that a tube is about to go?
thanks guys!
stilts1
atmasphere's avatar
atmasphere
11,662 posts
 
The EL509 is probably your best bet if you plan to update the amp for a new output tube, given the scarcity of the 6LF6s.

If I were you I would contact either Altavista or Rodger Modjeski, who put in a lot into the design of this amp.

Good Luck!
stereo_phile's avatar
stereo_phile
32 posts
 
I have such large stash of 6LF6 GE NOS tubes that Roger Modjeski graded and matched for my Counterpoint SA-4 amp. Back in 1988, I found out the tubes were being discontinued so I bought a stash of 250 tubes.
jw94055
125 posts
 
Check out tubemonger.com. Easy to work with. Good luck.
happynick's avatar
happynick
58 posts
 
I say if it sound good and isn't ringing or very bright,keep it! Old tube radio's from the 40's many of them have the same tubes in them and I regularly find an old dynaco 70 with original tubes for sale that the sellers says they check out fine,so perhaps just have them checked out by a tech and if they are within specs,hey spend the money on a weeked vacation or whatever.that's my opinion,Nick
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