From: lcargill99@comcast.com   
      
   I'd like to "design" and implement a simple 12AX7-based   
   buffer for musical instrument DI purposes. I'd like the   
   output to be balanced for ... no good reason at all   
   beyond having balanced inputs to play with.   
      
   My questions are:   
      
   - Do I really need 300V for this? What's the trade here?   
   - Is there a nice single-package, preferably   
   switchmode power supply that does 300V and 12.6V   
   heater, or am I in purely linear PS territory?   
   - Can I use both halves of the 12AX7 in triode to   
   achieve balanced output?   
   - Do I need an op amp for balancing, or can I do it   
   with just the 12AX7?   
   - How hard is it to add switches to make the circuit single-ended   
   and the output unbalanced?   
      
   The input will be unbalanced and potentially hi-Z. I can afford   
   to buy a nice tube DI but I haven't built anything in a long time.   
      
   Thank you for any responses that follow.   
      
   --   
   Les Cargill   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)