Whats on your turntable tonight?

Agreed, wouldn't do anything right now. 

I am wondering if the tube in the weak channel may not have been fully seated? If it was bad tube, it should have followed to the other speaker when you switched them.

I wouldn’t do anything more Brian just yet, keep an ear on it, maybe one of the sockets loose, pin bent, dirt, reinserted fixed it….hopefully for good. in future, i switch cables L to R to isolate to a component, you may have done that to arrive at phono preamp…. You have find decent B and K Tube testers for $75 - $100 ish also. w Tubes spares are your friend…

@noromance ya man, that’s where i got my copy from as well Brian. Enjoy…

i am toooooooo tired to spin vinyl tonight, work and early getups all week are a nasty combination….

That T. Rex "Greatest Hits" (according to the sleeve)  is actually Electric Warrior. Weird.