Here is a chart I made in response to a question about direct 12ax7 substitutions. There are more than most people realize. The RCA manual designates the pinout as "9A", so I've included all "9A" pinout tubes here.
I've included all the industrial and military designations of these tubes also (where applicable), and arranged them in order of amplification factor. I did not include European designations like ECC83, etc. Hope this helps someone with their experimentation. As for which of these will work in certain applications, you'll have to do more research and conduct your own experiments. Generally, if a 12ax7 is called for in a certain position in one of your amps, probably any of these tubes will work as a drop-in substitute. The lower the amp factor, the less gain you'll get from that stage, which might be desirable. If the stage is a cathode follower and calls for a 12AT7 or 12AU7, subbing a 12AX7 or another of these tubes might create issues. I encourage you to experiment. This would actually make for a nice video comparing as many of these as possible. I think I have most of them in my tube collection already. If you'd like to see a video like that, let me know.
Drive around with me trash picking while talking current events and personal philosophy.
This is a clip that I normally just discard at the end of a project. It's an extended and unedited jam session from which I took all the guitar clips for the recent D'Angelico Double Cut demo. Originally recorded in 4k, the full clip is 16gb large, which explains why I don't usually save these clips once a project is complete. Saving all the clips from these video would mean I'd eat up hard drive space in no time, so I always just delete them. This time, for giggles, I figured I'd reduce this down from 4k to 1080 and upload it here to preserve it. It's just raw camera mic footage, but it's fun to see how much stuff gets discarded when I edit this stuff down. It might also be fun for some of you to see how I usually go about recording demos. As you can see, I just start jamming and see what comes out. Some of it gets used and most of it hits the cutting room floor. This was the first time in about 6 weeks that I had picked up a guitar after my back injury, so it felt really good to ...
A few years back I saw a 412 cabinet at my local Music Go Round. It was built by a company I didn't recognize, but I did a little research and found out the cabinet was from the early 70s and, if the speakers were original, would contain 4x Celestion Green Backs. I borrowed a screw driver from the guy at the counter and opened the cab. Sure enough, there were 4x early 70s Celestion Green Backs. I traded them to a guy in Asia for a half ounce Canadian Gold Maple Leaf. I paid $100 for the cabinet. Today, gold hit a near all time high close to $3000/ounce. I sold that half ounce bullion round for $1500. THAT is how you score at the music store, my friends.
