I could use a little guidance as someone fairly new to tubes . I've built a guitar amp by copying a schematic but now I'm heading up the learning curve and trying to create something similar , a clean low -power amp , from bits of old radios etc. I have a 6p25 output valve and OT (same spec as Pen 45 only 6.3 volts heater) and the schematic for the radio it came from , now I want to add a different driver/preamp stage . However , it's hard to find information about matching preamp valves and output valves - can someone enlighten me or point me towards a link ? I have 12ax7 and EF86 available , but I'd like to know how you go about deciding which valve to use . Can you do it by basic valve data ?Or by lengthy calculations /Tubecad . From looking at schematics I never see 12ax7 with Pen45 type valves , so I presume there is some mis-match . Also , as an aside , I find a lot of stand-alone preamp designs , but not stand-alone power amp , is there a reason for this or have I just missed them?
Anything that can point me in the right direction much appreciated.
Anything that can point me in the right direction much appreciated.