Originally Posted by Grumus
I have a question. I just ordered all the parts for the 19J6 build because I got two tubes for 12 dollars. But if they don't work or I need to replace them in the future I might have to rebuild it for 12AU7 if I can't find any 19J6s. Will the mounting holes for the tube sockets line up between the 9pin and 7pin? I don't want to wreck the case if the mounting holes aren't the same. Should I just buy the parts for 12AU7 and then drill and build everything according to that from the start?
A 9-pin socket is bigger than a 7-pin one. So no, the mounting holes will not line up. If you are simply punching holes for the tubes in the top of the case, as in with a PCB- or perfboard-mounted sockets, then the same hole that the tube pokes through can very easily accomodate a 9-pin tube. 1" is a good diameter that will work for both.
If you're mounting the sockets to the case, you won't have an issue, either. Drilling out the hole to accomodate a 9-pin tube socket will "clear out" the 7-pin socket's mounting bracket holes. This is easily shown comparing the dimensions of the most-used new-manufacture ceramic sockets:
(7-pin socket pic from vacuumtubesinc.com)
and this one:
(9-pin socket pic from vacuumtubesinc.com)
Here are the comparative dimensions:
28mm on-center mounting holes (2)
22.5mm on-center mounting holes (2)
As you can see, drilling out the hole for the 9-pin socket in the future would leave 1/4mm of the 7-pin bracket mounting holes on either side of the socket hole (22mm hole for the 9-pin socket vs. 22.5mm on-center mounting holes for the 7-pin). That's not enough to even worry about. You will also have to drill new mounting holes for the 9-pin socket, but the socket's top rim, bracket, etc. will cover any overage.
Edited by tomb - 3/8/13 at 7:01am