Vacuum Tubes: Episode 8 - 24V Vacuum Tube Shootout (Triodes, Pentodes, and Pentodes as Triodes) 

I’m absolutely loving playing with these old tubes! I do actually have a few 6J6 tubes! Interestingly, IBM also used the 6J6 (or whatever the ruggedized equivalent of it was) in some of the tube computer designs. Since IBM designed their inverters with the cathode tied to ground, it worked out quite well to have a dual triode with a shared cathode. I have done a bit of testing with them at low voltage, and they’re a little too linear for just 24V. I imagine they make quite good audio tubes! In my testing at 24V, you really gotta bring the grid voltage pretty high in order to get the tube all the way into saturation. I have indeed seen some of the old car tubes that were designed for 12 volts, but I haven’t gotten my hands on any of them yet. I’d love to play around with them and see how they perform versus a high voltage equivalent like a 12AU7. Weirdly, aside from my most recent little low voltage audio amplifier, I’ve only played with tubes in digital circuits, which is a pretty unconventional way to be messing with them, haha. But, you are definitely right in that they look way better than little black IC chips!

Thank you so much!

The classic multivibrator is one of the greatest designs! It's super easy to implement and make a nice oscillation! Though, I'm a bit more fond of the Hartley oscillator if I'm honest.

I got lucky on eBay once and got a lot of 600 tubes for mega cheap. I'll never use all of them, but the two days it took to sort them all was so relaxing, I keep an eye out for big lots of tubes just so I can sort them again! Keep me updated on your low voltage adventures for sure!

Thank you so much for the support! Good catch on the LED! I filmed that last outro a few times and then spliced some video and audio together. It all went together really smoothly, except the LED. I’d like to chalk it up to ghosts, but I think I can safely blame it on the human and DaVinci Resolve instead, haha. I actually split the overall data collection up across two days because I was running out of time on the first day. About 2/3 the way through the time lapse, the camera position changes slightly and that’s actually the beginning of the second day of testing. Even though I split it up across two days, in total, it was maybe four hours of testing, so it could have been done in a single day. Not too bad, but definitely not a quick test! Your wondering about stability is definitely not unfounded. My personal projects are a bit further along than what we’ve built in videos, and there are some definite issues when stacking multiple gates back to back. If we were running 150V on the plate, like IBM with the 604, we’d have a much easier time. With that much voltage, a 5V discrepancy due to tube age or even not getting the values of the resistors picture perfect doesn’t really affect much. At 24V, a 5V discrepancy can cause huge issues! But, these are all problems we’ll tackle as we get deeper and deeper into building more complex stuff. Thanks for the compliments on the new logo! I wanted to bring this channel closer inline with my other hobby/channel, Usagi Motors (usagimotors.com/). I’m super pleased with how the vacuum tube eared bunny logo turned out though, haha.

@@UsagiElectric OOhh I see. Thanks a lot for the link, I'll check that for sure ! Therefore, I'm waiting for the next videos to see all of this ! See ya ;-)

@@antoinestevan5310 Thanks for checking it out! Editing the next video up now, it should be a fun one!

If I had to venture a guess, I would say it was due to size. A lot of octal tubes got replaced with smaller, heptal or noval tubes to miniaturize components as much as possible. Even the venerable 6SN7GT got miniaturized into a noval package and labeled the 6CG7/6FQ7. I suppose with the advent of new cathode and anode technologies, and improved construction techniques, this made sense as tubes could be made smaller without sacrificing too much in the way of power or sound. Having said that, a properly set up amp with a suite of good octal tubes still sounds absolutely sublime!

Haha, I like that as a slogan - "Who wants to be in their right mind?" I think I'll have to make a shirt with that on it! Thanks for the kind words on the videos!

Interesting, the PCC88 is like a 6DJ8 with a 7V filament. That would make for some interesting connections when running the heaters in series. Here in the US though, they seem to be going for about the same cost as the 6DJ8. Most likely they weren't a popular tube here and that makes them fairly rare. Either that or I'm terrible at finding the cheapest places to shop for tubes, haha.

@@UsagiElectric to bad your not in holland we have a guy that has amazing prices www.electrontubes.nl/Voorraad/voorraadset.htm

The word he was looking for was probably "ubiquitous", but then one of the associative neurons misfired...

These data are of interest _because_ his B+ rail is ~24VDC. Further, he does not need linearity as needed in Class A amps; he needs more of a step function.

"nobody can process".. you mean "you can't process". I have no problem with it at all. It's just how he's used to saying it, and that's perfectly fine for me. Remember that he makes videos for you to watch for free. You don't have to watch them if it's too difficult for you.

Seriously. Just change “thousand” to “kilo-“ in your head. It’s not that hard considering how common “kilo-ohm” resistors are.