From: xtrchessreal@gmail.com   
      
   On Wednesday, September 30, 2020 at 11:41:25 AM UTC-6, Big Bad Bob wrote:   
   > On 2020-08-29 01:50, Xtrchessreal wrote:   
   > > The question is simple: When it comes to schematics e.g. I see V1A and V1B   
   How do I know which triode this refers to is V1A Pins 123 and V1B 678. Most   
   data sheets indicate pins 123 to triode two and pins 678 to triode 1   
   > >   
   > > In the Philips data sheet for a 12AX7 they even have a remark stating pins   
   678 or triode 1 is a better triode with regard to hum.   
   > >   
   > > Some schematics actually show the pins for the specific triode but most   
   only show V1A V2B V3B etc. Its obviously most critical in the first pre-amp   
   stage unless there is a reason by the designer to have something a little   
   different.   
   > >   
   > > Can anyone explain this convention or lack there of?   
   > >   
   > yeah it's a little disturbing they're not being precise.   
   >   
   > Only other thing I would do is look at the GE tube manual for how they   
   > draw it, and maybe infer pin numbers and "which triode" from that.   
   >   
   > which tube is it, 12AX7 or ?   
   >   
   > The GE manual I'm looking at shows "section one" on pins 6,7,8 and   
   > "section two" on pins 1,2,3. So I'm guessing 'V1A' would be section   
   > one, and 'V1B' would be section two. If you look at the actual   
   > equpment, maybe you can trace a pin to a component to verify?   
   >   
   > assembly was often "by hand" back then with point-point wiring. The   
   > schematic could be "the other way" and it still got built right. I   
   > would expect they're all consistent within themselves, but when compared   
   > to other gear... who knows?   
      
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