That was easy! Ok .. moving on.. Wait.. What’s that you say? You want to know why? Really?
Well, alright.. if you are that bored.
As we saw before there is little variability out there for the output tube in these amps. 6V6 and 6BQ5 are very different tubes but they are rated roughly the same. I dug through a lot of low power tubes looking for, a) low power and b) availability and proven use. Didn’t really find much. 6G6 and stuff like that looked promising enough, but I had an epiphany that led me to the 6AQ5: I have a box, with the right sized Iron for 6AQ5s, with a socket in place, and all the room I need.
I’ll talk about the tube at length later, but since I am converting an amp that had two of them in P-P, I know I have the heater current, source voltages and OT ability to run one and then some. When I realized that this made some sense, I grabbed the 6AQ5c – EL90 Datasheet to see what kind of power the thing puts out. I knew the amp ran 8-10 watts in P-P so I figured the tube would be a little louder than I was hoping for. In fact it’s maximum signal output power is 4.5 watts @250V and 2 Watts @180V. The 6v6 is almost exactly the same tube but it can take a higher voltage on the plate (315V) and push 5.5 watts. Both Fender and Gibson SE amps of the 50’s pushed near 315V on a 6V6.
So, I would have liked to have used a tube with less output (so I can drive it hard at low volumes) but this will do nicely as everything is already set up for me.