Tubes Asylum

12au7 to 12bh7

178.85.164.155

ianvanniele@gmail.com

Proud owner of unison research little italy amp.I would love to know if it is possible to change de 12au7 tube for a 12bh7 tube without any damage to the amp

Follow Ups:

RE: 12au7 to 12bh7 - TubeAcolyte 12:34:06 06/21/17 (4)
Hmm, well, a 12BH7 draws 0.6A @ 6.3V for the heater, twice that of a 12AU7. Save for that, the other specs are close enough that it's almost a drop-in replacement altogether.
Looking up the amp and breezing through the manual, there are no mentions of transformer's heater winding specs, so it's tough to say.
There are four suggestions I can offer:
-Ask the manufacturer directly.
-Try to source out the part# and manufacturer of the power transformer. If you can get a datasheet, you'll likely find your answer.
-If you have the experience and don't mind voiding the warranty, you can measure the heater voltage before and after. If it drops below 6.3V with 12BH7s in the place of the 12AU7s. If it does, don't use them, and flip back to the 12AU7s.
-EDITED FOR POSTERITY (after Jim's correction): There may be a noticeable/measurable difference in the heat produced by the transformer.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
May your tubes be lively, warm, and long-lasting. Holy be thy heater.

Edits: 06/21/17
- RE: 12au7 to 12bh7 - Jim McShane 15:02:42 06/21/17 (3)
  -Lastly, measure the power transformer's temperatures before and after the installation of the 12BH7s. I'm not sure what the maximum rating would be (especially for your case), but from my understanding anything hot to the touch is a no-no. Warm is fine, but not on the verge of burning.
  Not true! Even cheap trafos are rated for much higher than the 130 F or so temps that makes it too hot to leave your hand on more than a few seconds.
  Your post had a lot of good advice - but a power trafo at 150 F is just loafing.
  Edited to fix typo...
  
  Edits: 06/22/17
  - RE: 12au7 to 12bh7 - TubeAcolyte 15:35:46 06/21/17 (2)
    Hmm, I didn't know! Thanks Jim! 130-150f... Or 55-65 Celstickles for us Canucks xD
    I haven't really gone out of my way to touch at those ranges lately, but I imagine it would be a kind of heat that you could actually rest you palm on for a few seconds. Coffee warmer, by the sounds of it!
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    May your tubes be lively, warm, and long-lasting. Holy be thy heater.
    
    Edits: 06/21/17
    - Temperature Scale Conversions - Eli Duttman 16:53:35 06/21/17 (1)
      F ^o = (9/5 C ^o ) + 32
      
      C ^o = (F ^o - 32) (5/9)
      
      It's pretty darned easy. BTW, Fahrenheit is better for weather, as few measurements are outside the 0 to 100 range.
      
      Try doing industrial problems with Rankine temperatures. ;> ) Rankine is an absolute temperature scale employing the Fahrenheit degree.
      
      Eli D.
      - or - Ross 18:57:13 06/23/17 (0)
        
        In Reply to: RE: Temperature Scale Conversions posted by Eli Duttman on June 21, 2017 at 16:53:35
        
        C x 1.8 + 32 = F
        
        F - 32 / 1.8 = C
        
        Decimal math is easier to do your head (at least in my head).

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