SET Asylum

6080/6AS7 much less linear than 300B.

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Thomas Martens

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In Reply to: 6080/6AS7 in SET design posted by b.ben on February 27, 2007 at 23:16:48:

6AS7 tubes commonly used in OTL type amps which use large ammounts
of inverse feedback --and therefore effectively increases linearity.
For zero feedback SET amps --I'd probably shy away from 6AS7.
Also: 6AS7s require lots of heater current, generate lots of heat,
and in my experience can become quirky and drift with age.
I'm not saying there are not some decent 6AS7 amps out there,
just that IMO there are easiertubes to work with for SET.
-T.M.

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Re: 6080/6AS7 much less linear than 300B. - Paul Folbrecht 20:55:30 02/28/07 (2)
Don't the A-M OTLs use 6AS7s with zero feedback?
- Don't know, but whichever, this in no way invalidates my statement - Thomas Martens 10:48:39 03/02/07 (1)
  -T.M.
  - Yes it does... - Ralph 11:35:03 03/05/07 (0)
    The 6AS7G came out of the 2A3 design work and was intended as a voltage regulator and audio amplifier. For both they have to be quite linear and a look at the curve shows that there is very little difference between 6AS7Gs and most DH triodes.
    We've been building zero feedback OTLs for nearly 30 years and as such have been building triode amplifiers longer than anyone else currently in business. I think we'd know about linearity issues in the tube by now :)
    Operated single ended they offer the same linearity, its the transformer that will be challenging as to get power single ended, you will have to run parallel sections. Its not a high power tube.

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