From: info@turneraudio.com.au   
      
   On Tuesday, 19 January 2016 05:52:28 UTC+11, tub...@gmail.com  wrote:   
   > Hello!   
   > Which tube is equivalent to 1/2 12BH7?   
   >    
   > Thanks!   
      
   Quite a few comments on 12BH7.   
   Its about equal to having two 12AU7 in parallel.   
   The Ra for 1/2 12BH7 is half the value for 1/2 12AU7, but µ is nearly equal,   
   so BH7 has higher Gm.    
      
   This means that for a given B+, RLa and Ea and Ia, BH7 can swing a wider   
   voltage before Ea swing is limited by Ra curve for Eg1 = 0V. The lower Ra   
   means F response extends to higher F. Because it swings wide, its an ideal   
   driver for output stages needing    
   high Ea swing, such as in McIntosh amps.   
   I've used BH7 often for rebuilds when I found I had them around - its a very   
   good driver, IMHO.   
      
   The only equal tube I know is 6BL7, but that's an octal tube, but then a quite   
   fabulous twin triode with fabulous reputation same as 6SN7, or big plate 6CG7   
   which are 9 pinnie versions of 6SN7s.   
      
   When I first built a decent preamp in 1994, I tried SRPP and I could not tell   
   any difference in sound between 12BH7, 12AU7 or 12AT7 in a line stage amp; you   
   can build the SRPP to suit all 3 without changing Rk. IN SRPP, there is no   
   RLa, the tubes are in    
   series with no anode resistor. But signal is less than 1Vrms, so no matter   
   what you use, it works, and you only have to worry about gain.    
      
   Patrick Turner   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)