Tube Lab #6 12AX7 Tube Rolling

[@voxpathfinder15r]

I have been looking at 12au7’s lately for my guitar amplifiers. Been looking at schematics and noticing that starting with the 2nd gain stage, 12ax7 tubes are really not necessary. Sure the 12au7 aren’t high gain - but they can swallow a huge signal on the grid the 12ax7 just can’t. I have a 17 volt peak to peak signal coming off the first gain stage of my Carvin Belair with a 150 mV input signal. I don’t need a 12ax7 for the 2nd stage. Just going to rework the plate and cathode resistors.

[@thomkopal1740]

Some additional considerations for your discussion of Mullard ECC83 tubes... - The etched code is almost always visible, at least in part, on the lower side of the glass. If you can't see it, try in full sunlight. If you still cannot see it, there are some additional tricks for distinguishing a British Mullard from nearly identical Philips-style construction on ECC83 from Matsushita (Japan) and BEL (India) - two lookalikes that rarely put an etched code on their ECC83s. - Startup flash is not a consistent indicator of Mullard/Blackburn origin. Not all the Blackburn Mullard ECC83 flash on startup. Nor does the startup flash necessarily indicate European origin. For example, some early-'60s US-made CBS 12AX7A also exhibit this flash. Look for those etched codes!

[@dustindario4569]

i dont mean to be offtopic but does anyone know of a trick to log back into an instagram account..? I was stupid lost my account password. I love any tips you can give me.

[@judsonfrancis3659]

@Dustin Dario Instablaster :)

[@dustindario4569]

@Judson Francis Thanks for your reply. I found the site on google and Im trying it out now. Seems to take quite some time so I will reply here later with my results.

[@dustindario4569]

@Judson Francis It worked and I now got access to my account again. I'm so happy:D Thanks so much you really help me out :D

[@judsonfrancis3659]

@Dustin Dario Happy to help :D

[@geraldmosley2195]

Hey, Mr Jim. Great video, but I have a question ❓ how do you find the number value on a tube, when the markings are rubbed off , can you share your tricks, please, thank you

[@tubelab194]

Sometimes a bright lite and some angling to catch a faint remant will work. But mostly we rely on our experience and it helps to have a large inventory to compare an unknown tube against. Charles is a genious when it comes to figuring out some difficult to identify tubes. If you are stuck, join a FB group dedicated to vintage tubes, post a couple of high res pictures and only ask about ONE tube at a time.

[@ecc8344]

Awesome! :)

[@lorencing]

The big question is does that filament flash deteriorate the material quality, it usually happens on one or two filaments, not on all, so I wonder how that affects the long term reliability of that tube as one or two filaments are exposed to much higher temps.

[@tubelab194]

Good question! In my experience some of the worst testing (Gm and noise) used vintage tubes are the Mullard miniature 9 pin types and these almost all have the flash. Now Mullard had a rep "back in the day" among repairmen for being noisy, so this may well be just another issue, seperate from the filament design. The problem of course is Mullard isn't making anymore of these wonderful sounding tubes, so we just need to carefully weed out the noisy ones and make good use of what's left to us.

[@shutupdog11]

Hey Jim , wats equivalent to a 824 tube for phono stage ?? Thanx in advance !! Id like to order those gold pin gold lion and try them ...

[@tubelab194]

I have no (zero) idea what 824 you are talking about. There is a cv824 which is a 7 pin transmitting pentode, definitely not a phono tube. Commonly used high gain tubes for a phono stage are 12ax7 and 6sl7.

[@shutupdog11]

@tubelab194 Yep ,2 , 7 pin came on a small phono stage preamp that I had purchased off Amazon . (Grin ) Fosi Audio is the maker of the preamp . I'm super new to tubes but very open minded so I tried this little piece and love it . The sound was what I would call crisp , spongy , (w guitars on a first press Lp ) I'm really digging the sounds it brought to my system . The 2 tubes it holds do have 7 pins . Thanx

[@DreidMusicalX]

Ive al;ways just played guitar and never really got into the nerdy part of my amps too much before. Can you use two different brands of tubes in your amp at the same time? Like say Mullards pre amp tube with Electro Harmonic power tubes as long as they match the specifications of the amp, instead of all just the same brand in the pre amp and power tube section?

[@tubelab194]

Absolutely of course you can mix and match different manufacturers. In fact in the various sets of tubes we offer for Schiit amps and the R8 we do exactly that, choosing the best sounding tubes for each slot.

[@stevenhifi2188]

Hi I have mullard M8137 CV4004 KB/D military spac. What's different is?

[@tubelab194]

CV4004 is just the UK military designation for the 12AX7, CV stands for common valve. Was the tube any different, maybe, but in many cases the tube was the same one the manufacturer sold domestically and labelled as a 12AX7 / ECC83. Unfortunately data sheets aren't always available to compare the two, but go ahead and try and find them both with a Google search, then you can compare them.

[@wmk0100]

Hi Jim, Have you ever tried the 6N2P ? They say with the adaptor it can directly replace the 12AX7. For about $15 I bought 8 tubes and an adaptor to play around with. We shall see.

[@tubelab194]

Hmmm I doubt the adapter will work, main difference is heater voltage, the adapter probably says for 6v heated 12ax7, most today are set at 12v, won't work if your heaters are 12v. Take a look for my 6n2p video, I talk about these issues in detail.

[@tubelab194]

kzbin.info/www/bejne/pGK2XnV6i6-Khac

[@wmk0100]

@@tubelab194 All the amps I build get 4-5 jumped so I power the tubes with 6.3v, I'll have the check the pinout on the converter to see if it takes filament voltage between 4,5 and 9 or just between 4 and 5.

[@cal629195]

A second hand Telefunken 12ax7 costs only usd50 and sounds much better than any other European ones .

[@Furax02]

How do you feel about real Telefunken 12AX7s?

[@tubelab194]

I don't get a lot of Telefunken 12ax7's in, one of my wholesalers had 4 up for sale a while back and I couldn't bring myself to pay what he wanted. Now I regret not buying them - prices having continued to go up at a crazy rate! My main focus is finding excellent - affordable tubes for my customers.

[@thomkopal1740]

Real Telefunken 12AX7s are one of the most commonly counterfeited tubes, with re-labeled Ei/Yugoslavia ECC83 often being the true origin. Look at the glass between the pins for a nearly-square "diamond" shape embossed in the glass for one way to assure you are considering the real Telefunken. There is another great way to spot a true Telefunken, by looking at the point where the getter ring connects to its support rod, but that is a little complicated to convey verbally. Also note that there are "smooth-plate" Telefunken ECC83, as well as "ribbed-plate" Telefunken ECC83. The smooth-plate gets all the attention, because it has a unique sonic character. Those smooth-plate TF ECC83 have a response peak in upper midrange frequencies that no other ECC83/12AX7 has. The low frequencies are not very prominent, and they are very well-defined. And there is actually a roll-off of treble with the smooth-plate version. These characteristics are relative to other 12AX7 types. The ribbed-plate Telefunken ECC83, by comparison, allows a more extended range of frequencies to pass - with deeper lows, and more prominent treble. I actually prefer the ribbed-plate myself, but many home audio enthusiasts enjoy what the upper-mid peak of the smooth-plate Telefunken ECC83 does to the human voice, so there is no "best" choice (only personal preferences).

[@Furax02]

@@thomkopal1740 I have both legit Telefunken and vintage Ei ECC83 tubes, and sonics are clearly different.

[@ColocasiaCorm]

Kevin spacey

[@hgim82]

Please don’t shake the tube while talking!

[@tubelab194]

Yes, i've noticed that I get excited sometimes and the shaking gets worse! These vids are scripted, but get taken in the "one take" format, no editing, so if I have a minor issue, I just keep going! Watch on friday and let me know if i've improved!

[@tubelab194]

Thanks for your input!

[@hgim82]

@@tubelab194 It’s a good informative video. I enjoy it. Can you show exactly what the D-getters and O-getters etc. are? Cheers!

[@tubelab194]

@@hgim82 in a future Tube Lab for sure, I'll watch for tubes that have distinctive getters or maybe an entire episode on tube characteristics, though that may put most viewers to sleep! Cheers, Jim

[@mns8732]

Thank you Biden for hampering American rockers to rock out.( by issuing sanctions on Russian tubes) Rock and Roll: the only American export everyone loves. More rock and roll, less bombs.(

[@MichaelScottPerkins]

Uhm... really? 🙄

[@nichesound]

so invading another country is fine though...moron

[@falconquest2068]

It's amazing to me how many people wear their politics on their sleeve. And it always seems to be "those" types.