From: pallison49@gmail.com   
      
   Les Cargill wrote:   
      
   >   
   > 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.   
   >   
   >   
      
   ** When you wake up from your dreaming, consider building something practical   
   and affordable like a JFET input DI - plus hum and noise free.   
      
   At the bottom of his page is the schem for one I designed:   
      
   https://www.talkbass.com/threads/have-an-h4n-recorder-do-i-need-   
   -di-box-to-connect-a-bass-di-schematic.1331245/   
      
   It use the "48V phantom" supply included in the vast majority of mixing desks,   
   even budget ones.   
      
   The output transformer is a 10K to 600ohms type and not expensive.   
      
      
   .....    Phil   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)