Bogus 12ax7 tubes.

[AlNewman]

I just saw a video from Mr. Carlson's Lab, where he mentioned a lot of modern tubes labeled 12ax7 are actually 6dj8 tubes with different filaments.  Anybody experience this?  Which manufacturers are doing this?

[PRR]

Same reason McDonalds hamburgers are not made with worms. True 6DJ8 are more valuable than 12AX7. Even fake 6DJ8 have gone up in price. Also the amp-factor is enuff lower, and the heater drain enuff higher, to matter.

There's a Russian tube that the youth of today use "like" a 12AX7. Don't recall the type.
--

6N2P, (Russian: 6Н2П), also sometimes spelled in English "6H2Pi"
https://en.wikipedia.org/wiki/6N2P
http://www.r-type.org/exhib/abn0001.htm

[mresistor]

Some interesting information on the subject for those inclined    https://en.wikipedia.org/wiki/6N2P

[kagliostro]

Russian Seller say

6Н2П (6N2P) are same of 12AX7 only 6.3v heaters

6H23П(6N23P) and 6H1П  (6N1P) are same of 6DJ8 (E88CC or ECC88)

Here you can do search and find correspondent tubes

https://tubes-store.com

Franco

[AlNewman]

Same reason McDonalds hamburgers are not made with worms. True 6DJ8 are more valuable than 12AX7. Even fake 6DJ8 have gone up in price. Also the amp-factor is enuff lower, and the heater drain enuff higher, to matter.

There's a Russian tube that the youth of today use "like" a 12AX7. Don't recall the type.
--

6N2P, (Russian: 6Н2П), also sometimes spelled in English "6H2Pi"
https://en.wikipedia.org/wiki/6N2P
http://www.r-type.org/exhib/abn0001.htm

I think the jury is still out on Mcdonald's.
If a company were to say rebrand the 6n2p as 12ax7 and modify the pinout, it probably wouldn't bother me much as they are identical in nearly every way besides a slightly higher heater current.  But to rebrand a 6dj8 is something else entirely, they have 20% higher heater current, about 60% less maximum plate voltage and about 60% less amplification factor.  Doesn't matter if they are worth more or not, they aren't designed for the same circuit.

[AlNewman]

I bought a few of these a couple months ago from a well known supplier.  They look a little dodgy to me, and they certainly have a different sound, but  I just assumed it was the brand and not the type of tube.  Would this be a 6dj8?

[tubeswell]

I bought a few of these a couple months ago from a well known supplier.  They look a little dodgy to me, and they certainly have a different sound, but  I just assumed it was the brand and not the type of tube.  Would this be a 6dj8?

Hard to tell with JJ. Quite a few of their tubes have 'different' electrode cages e.g., the '6V6S'

[AlNewman]

Well, also look at the wiring to the pins.  Kind of a dog's breakfast.

[kagliostro]

... slightly higher heater current ...

Philips ECC88 require 365mA for filament

http://www.r-type.org/pdfs/ecc88.pdf

6DJ8 is indicated as to be an ECC88

http://tdsl.duncanamps.com/dcigna/tubes/sheets/amperex/6dj8-1h.gif

so not all the tubes that are indicated as substitutes require 300mA (as the 6922)

http://frank.yueksel.org/sheets/049/6/6922.pdf

Franco

[AlNewman]

... slightly higher heater current ...

Philips ECC88 require 365mA for filament

http://www.r-type.org/pdfs/ecc88.pdf

Yes, the ECC88 does.  The 6n2P I think is somewhere around 330ma.  It's still 10% high.  And that's probably enough as to why it probably shouldn't be branded as a ECC83

http://tdsl.duncanamps.com/dcigna/tubes/sheets/amperex/6dj8-1h.gif

so not all the tubes that are indicated as substitutes require 300mA (as the 6922)

http://frank.yueksel.org/sheets/049/6/6922.pdf

Franco

I get that, but I think you may be missing the point.  If a tube is labeled 12ax7, it should be close to the

[bmccowan]

Kind of a dog's breakfast

I like that.
Anyways, it might be interesting to check what you are seeing there against the drawings here:
https://www.amplifiedparts.com/tech-articles/12ax7-comparison-current-made-tubes
BTW of the JJ 12AX7 types, I like the 5751 the best, it has a softer edge to it - less brittle IMO.

[PRR]

Kind of a dog's breakfast

I like that. ....

That phrase is not common in the US, and probably not where Franco is. I know the phrase from the writings of A Bertram Chandler, but never had a clear explanation.

"dog's breakfast
"dog's breakfast," which has been British slang for "a complete mess" since at least the 1930s. While no one took the time to write down the exact origin of the phrase, the allusion involved seems to be to a failed culinary effort, perhaps a burned or botched omelet, fit only for consumption by the mouth of last resort, Fido. As a vivid figure of speech meaning something so fouled up as to be utterly useless, "dog's breakfast" can cover anything from a play plagued by collapsing scenery to a space mission ruined by a mathematical error. "Dog's dinner," which seems to have appeared around the same time, means exactly the same sort of disaster, but has the advantage of being attractively alliterative. Both phrases are heard occasionally in the U.S., but are more common in the U.K. and Commonwealth countries."  https://www.urbandictionary.com/define.php?term=dog%27s%20breakfast

[isaac_teller]

https://vacuumtubesinc.com/index.php/hallofshame

[AlNewman]

I would think a dog's breakfast is all the leftovers from the previous (events).

Served lovingly to a loving (and likely ignorant) parade of hounds, who enjoy a quick treat.

(likely very quick.)

[glass54]

In Aussie "dog's breakfast" implies a real mess 
Possibly comes from residue on dining (room) floor, after a party of excesses, left for the dog to consume.
Relating to our interests/hobbies, dry joints, burnt insulation from sloppy soldering iron placement, incorrect lead dress, poorly fitted screws/nuts on transformers, swarf left in chassis and all those nightmare items.
 

[AlNewman]

In Canadian a dog's breakfast is just leftovers of everybody's shit they'd rather not deal with.  Solder joints don't matter much when you're swapping tubes.

[bmccowan]

Well going forward, a dog's breakfast will be the term I use to describe the wiring in early Gibson amps. I love their tone, but damn what a dog's breakfast to work on.

[mresistor]

"fit only for consumption by the mouth of last resort, Fido"   


I'd have to disagree with that statement. Throw out some mis-prepared foodstuff around here and watch what abundace of creatures appear to appetize themselves..   might even be human.

[HotBluePlates]

I just saw a video from Mr. Carlson's Lab, where he mentioned a lot of modern tubes labeled 12ax7 are actually 6dj8 tubes with different filaments. ...

Link?  Because context is important.

... a lot of modern tubes labeled 12ax7 are actually 6dj8 tubes with different filaments. ...

I bought a few of these a couple months ago from a well known supplier.  They look a little dodgy to me ...  Would this be a 6dj8?

Your photo shows a JJ ECC83S.

Once upon a time, Tesla made tubes in Eastern Europe.  They even made a 6DJ8/ECC88.



After the breakup of Czechoslovakia, the Tesla factory shut down and was re-opened under the name "JJ."  Today, JJ makes the ECC83S whose plate and internal structure greatly resembles what Tesla once used in the ECC88/6DJ8 tubes.



Things like the plate structure & getter support appear to have been borrowed from the old Tesla tubes.





However, if you pop a JJ ECC83S into a tube tester, it will exhibit the (higher) gain & (very much lower) transconductance of a 12AX7.  It will not test like a 6DJ8/ECC88.

Which is why I wanted a like to Carlson's video.  I've never seen him make a false statement, so presume what he said required the viewer to have a little background to apply the proper context.

[AlNewman]

I just saw a video from Mr. Carlson's Lab, where he mentioned a lot of modern tubes labeled 12ax7 are actually 6dj8 tubes with different filaments. ...

Link?  Because context is important.

Approximately 8:15, but the whole video is worth watching.  The guy's a wizard.

He begins by explaining how they rebranded tubes in the old days, but makes a specific point to mention modern 12ax7 tubes....without throwing anyone in particular under a bus. 

[HotBluePlates]

Approximately 8:15 ... makes a specific point to mention modern 12ax7 tubes....without throwing anyone in particular under a bus.

I'll wait to see whether he puts out a video supporting his statement.  I say that because a lot of 12AX7s today are all over the map, with most being weaker than "12AX7 spec."  But when you understand that a tube is a balance among Amplification Factor, Transconductance, and Internal Plate Resistance then you also see that a 6DJ8 won't fly as a "substitute 12AX7."

But his original example was about 6V6 being relabeled "6K6."  He spends a lot of time talking about "pentode" and "beam tetrode" to explain how one can identify a real 6K6.  Except the 6K6 was a 7w tube, while a 6V6 was a 12w tube with nearly the same heater requirements.  So if someone gave you a 6V6 marked as "6K6" you actually more than you paid for.

Now it could be the 6K6 was used in a part of the receiver where the 6V6's extra transconductance & output for the same drive signal upset the radio's alignment (probably not, but  ).  6V6 probably would have been just fine in the receiver.  And as for modern 12AX7s... we'll see if he elaborates on his comments.