Looks like theres 2 mods one is this by AFB :
Yes, basically you are trying to use only the first triode in the tube, so all the leftover pins need to be neutralized or at least out of the way. So, pins 1, 2, 3 & 9 of the 6BQ7A need to be bent or cut, while pins 4, 5, 6, 7 & 8 can be inserted in a sequence into the socket hole 3, 4, 5, 6 & 7 of your adapter. Next, you just have to link/solder pin 6 to pin 1, and pin 7 to pin 2 on the adapter (with pins 6 & 7 disconnected at the base), and voila! You get a single 7-pin triode!
And on post #3145 at the bottom gibosi speaks of a wiring harness that is linked to another socket with no tube this mod using the 2 triodes of the tube instead of one if i am not mistaken in the first mod. One thing thats not clear in 2nd mod is the ground part is that settled ? Thats what i think i know am i correct ? A complete procedure would be great in time when everything is settled and clear.
I tried to use both triodes in the tube, plugging the tube into the left socket and connecting the second triode - cathode, grid and plate - to the appropriate pins in a socket adapter plugged into the right socket.
However, there was a very strong ground hum from the empty socket on the right. As this ground hum is totally independent of the volume, I suspect that there is some kind of grounding problem relative to the two sockets. My suspicion is that it might be a result of the fact that both cathodes, left and right, are being heated through the left socket. The only idea I have had to date is to connect pin 9, a shield grid, to a chassis ground. However, as I do not have much hope that this will actually work, I haven't gotten around to giving it a try....