Thanks. Noise testing wasn’t mentioned on the pages I was looking at (primarily 12au7, 6550, 5ar4) so I wonder why he’s offering it for specific tubes. I wonder why he’s charging for it at all - if I buy a tube and it’s noisy then I’m sending it back and asking for a refund. I don’t feel the need to pay up front for that test, other than avoiding the PITA to return it.
That is peculiar. Maybe there are some sensitive applications for those tubes where you might want extra clean ones. Or maybe they’re more prone to noise. I hadn’t seen that service offering either.
Generally I would think that selling a noisy tube isn’t good for business. A lot of vendors up charge for matching, low micro phonics, high gain so to charge for the testing isn’t unheard of. Tapping a tube may be what he does to get a better measurement if he finds them noisy.
I’ve never had a bad tube from him but his measurement practices can be different than what others do.
I hope it works out for you! Not sure how common this experience is, but I had this crackling happen to a used Sylvania bad boy tube (one of a pair), and the tapping fixed/improved it for a while, but it eventually just died altogether. Was about a week or two.
Having read @Wes_S ’ advice, maybe that’s what did it. I was tapping while hot. Whoops…
The most I’ve ever done with a tube while hot is gently nudge it if I was getting static, just to reseat it in the socket.
I’ve got one tube that is staticky that is likely due to grid current, I doubt tapping would fix it but what the hell, I should try it. It’s the first tube that’s gone squirrelly on me. Too bad too, cause I liked it.
Tapping on your tubes is not a good idea unless you are trying to clear stuck debris attached to the cathode. Kind of a last resort exercise.
True, and I still only do that while the tube is cool, and definitely not hot or while running in amp.
Does anybody have suggestions for tube literature that might get me beyond tube basics, but that doesn’t require an electrical engineering PhD to understand? I feel like I’ve gotten through the baby steps of learning the difference between a rectifier, input, and power tube, some of the interchangeability, and so forth, but I’d like to try to get to more of the “why” and “how”. I’m guessing someone has written a book or textbook somewhere, and wanted to throw out the question to the experts.
Did some digging on YouTube, and this wasn’t a bad start: https://youtu.be/oHjZs0bNwEs
I have found this guy helpful. Now he’s more focused on guitar amps, but the tube theory is still the same. He also has a bunch of videos on how other parts of the amp works, like the psu, capacitors, overall amp designs etc.
Here are a couple of vintage black & white videos that may not be what you’re looking for, but I found interesting:
The first is an instructional video on how a tube works. The second was made by Mullard to explain how their tubes were made.
Below are some resources:
Posted some tube rolling impressions in the Euforia thread, thought it might fit in with this thread as well.
Super cool. Never really understood how tubes worked. Really amazing.
Hi everyone, haven’t been on here in a long time do to health issues,
Wanted to post this information for the owner of Tubemonger
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Nice to see you back @jb77.
Hi everyone, I am listening some of my 12au7 tubes for sale
- Mullard Blackburn goal post getter ECC82
- Brimar CV491/12AU7/ECC82 Long Plate Square Getter England 1958
- Valvo 12AU7 ECC82 Germany, Hamburg Made Tubes (GfO D9E), SlantedGetters
- Amperex 12AU7 BugleBoy
Hi everyone, I am listening some of my 12at7 tubes for sale
- Valvo Hamburg Pinched Waist 6201 double post O getter 1959 blue label
- Mullard Blackburn ECC81 56/57 square getter
- Mullard Mitcham ECC81 1956 square getter
- Heerlen E180CC/7062 1957 PW
Also listing my Hagerman Audio Labs Tuba (Tube amp) for sale