Tubes Asylum

Question on JJ 2A3-40 vs JJ 300B

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drlowmu

M

Hello,
I've never seen a JJ 300B of recent manufacture .
I own JJ 2A3-40s, and they have a LARGE cathode structure, harp-like, with about eight filament wires comprising the cathode, with a LINEAR spacing of the filament string, between the single plate walls. ( Most triodes have less-linearly spaced "V" or "W" shaped / small filament structures.)
My question is, ....... does the latest JJ 300B have the same "linear" harp-like filament / cathode structure as the JJ 2A3-40, OR, .......does the JJ 300B use the old fashioned " V " and " W " filament structure ???
Who has eye-balled both JJ type filament structures, and can tell us ???
Thanks !!
Jeff Medwin

Edits: 03/30/15

Follow Ups:

RE: Question on JJ 2A3-40 vs JJ 300B - Alpha Al 15:07:09 03/30/15 (3)
I have some JJ 300B's on the bench now. They have four "inverted v's" for a filament. Each V is hung from the center with a spring for tension. These may be several years old. I'm not sure if they are the current version or not.
- RE: Question on JJ 2A3-40 vs JJ 300B - Tre' 08:17:48 03/31/15 (0)
  It's my understand that "harp" filaments run vertical, side by side. Like the ones in this picture.
  Not Vs or Ws like the one you showed.
  In the end I don't think it matters much. The electrons do not leave the filament and go directly to the plate.
  They instead leave the filament and go to replenish the "cloud" and then leave the cloud for the plate. This, IMO, makes the orientation of the filament wires much less critical because it's the cloud's orientation that's important and in a healthy tube the cloud is large, filling in all the spaces between the filament wires, etc.
  So the symmetry of the cloud (WRT the plate) matters , not the symmetry of the filament wires (WRT the plate).
  Tre'
  Have Fun and Enjoy the Music
  "Still Working the Problem"
  
  Edits: 03/31/15 03/31/15
- RE: Question on JJ 2A3-40 vs JJ 300B - drlowmu 15:14:32 03/30/15 (1)
  THANKS,
  
  That answers it, my 2A3-40s, two years old, look identical !!! Nice filament rack !!
  Thank you very much.
  Q. : How do people like the 300Bs from JJ, consensus-wise, versus others ??
  Such filaments in these two JJs is not the same as, but it "approaches" what AVVT and Emission Labs might do.
  The JJ 2A3-40s are really great for the $$$$$$.
  Jeff Medwin
  
  Edits: 03/30/15
  - RE: Question on JJ 2A3-40 vs JJ 300B - vinnie2 03:31:12 03/31/15 (0)
    Can't compare them to anything else because I have used the JJ 300B exclusively in several iterations of my amp and in my bread boarded 91A. I have been very happy with it and never saw any reason to change. Must admit though that I would like to try a WE one of these days if I could borrow a pair for comparison. : )

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