12au7 vs 12au7/ecc82 or 5840 vs 5840/6225

[fatfoohy]

what is the difference between a plain 12au7 tube and a 12au7/ecc82 or a ecc802/12au7? or even a 5840 and a 5840/6225? are these just different names for different countries, or do they mean that the tube will behave differently, or would they be interchangeable?  If anyone has any insight it would be greatly appreciated.

[tubelectron]

Hi,

The 12AU7 is the US reference of the European double-triode ECC82 : this is the same tube. In our audio applications, they're fully interchangeable. There is also a russian cyrillic name for the 82, but I don't remember it on the spot...

Improved versions are E82CC, ECC802, ECC802S (Germany); ECC82***** (France); 12AU7WA, 6189, 12AU7A (military / industrial); B339, CV4003 (England), to name the most common. Improvements are usually on the microphonics, stability and compliance to the datasheet, life expectancy, etc...

Sometimes a different name is only a manufacturer's gimmick. Look at the Groove Tube's designations, amongst others : cabalistics 12AU7RRCTWZHA3GLLOQNOSUSA and so on. Each year there's a new one, nothing to do with the vintage official designations...

The 5840 is a VHF subminiature pentode, as is the 6225 - I didn't have the time to compare datasheets, sorry, so I can't tell you if these are equivalent.

A+!

[fatfoohy]

wow! thank you so much for your help! I couldn't have asked for it any more clearly.  I will compare the datasheets later today and see what i find out in case anyone else has the same question. thank again for sharing your knowledge

[fatfoohy]

The only large difference seems to be in the plate resistance, for the 6225 it is 175k, and the 5840 it is 260K. Here are the datasheets
6225- http://www.nj7p.org/Tube4.php?tube=6225
5840- http://www.nj7p.org/Tube4.php?tube=5840
My only question is, does this mean that the 6225 is not a direct replacement for the 5840? or is that not a big deal?

[panterafanatic]

The difference between the ECC82 and ECC802 is I believe the ECC802 is a long plate version. Otherwise they are the same, the difference is nomenclature (they're both 12AU7)

http://www.tubesandmore.com/scripts/foxweb.dll/moreinfo@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?item=T-12AU7-JJ
http://www.tubesandmore.com/scripts/foxweb.dll/moreinfo@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?item=T-ECC802-S-JJ

http://tubedata.tigahost.com/tubedata/sheets/127/5/5840.pdf
http://www.nj7p.org/Tube4.php?tube=6225

The heater current is slightly different. 1 requires 150mA, the other 175mA. So that's basically negligible. Interelectrode capacitances are basically the same. The transconductance is a little different, 5000 usiemens  the 5840, and 4500 usiemens  for the 6225. So the headroom will be a little different. But I would say that the screen voltage has a much bigger play on the headroom.

Edit, it's a good bit higher of an internal plate resistance, but that may not be a large role depending on the circuit, if it's followed by a buffer or something for use as a pedal, it still should work.