well I can tell you thats not a 6V6, its entirely too big. I can make out "GC", so I'm going with 6L6GC. If those are the tubes that came with it, solid guess they are installed for a reason.
Single tube, probably good for ~6 watts or so, depending on exactly how its biased. Its a homebrew of some description but probably not a very complicated circuit. Single ended amps almost can't be complex, there just aren't enough parts in there. Should be easy enough to draw up a schematic..
Pinout wise most of the power tubes are the same, the big difference is how it biases and the voltage applied. Without those values its impossible to say if a 6V6 or a 6L6 makes more sense. A 6L6 will plug in and usually function where a 6V6 does, but a 6V6 at 6L6GC voltages and current will not survive. "
Similar with that first tube, all of the 12a*7 use the same pinout, but work into different loading. The 12ax7 tends to work with the smallest cathode resistors and largest plate resistors in that group since it has the highest gain but runs at the lowest amount of current and bias voltage.
