12Axx/ECC8x vs industrials

[soundbrigade]

I had to get three ECC82/12AU7 for a preamp but bought 5693 (GE) instead. Not believing that numbers on a tube makes any difference, I still must confess that I am curious - is there any difference between "standard" audio tubes like 12AX/AT/AU... aka ECC81/82/83 ... and their respective "industrial" types?
Russian tubes can often be optain with an added -E or even -EV, which signals that the tubes are mechanically more stable, but can I expect something like this from the 5693?

[EWBrown]

From my own experience, I've found very good consistency wih the "industrial" tubes, 5693 is good, as is 6189, they are very close in operating characteristics to 12AU7 / ECC82. 12AU7 is actually more of an RF tube, though it is very common usage in audio. I found from testing a few 6189s in the Poseidon and ST70 drivers (with CCS long tail) that the 6189s showed better matching between the two triode sections, than did random 12AU7s. I have not tried 5693s in that application.
6CG7/6FQ7 are also very good, but they have the 6.3 V filament connections to pins 4 and 5, and 9 is either unused, or an internal shield. The 6CG7/6FQ7 is the 9 pin miniature version of the 6SN7, whichis an excellent audio tube. There are also 8 volt filament versions of the 6CG7/6FQ7 and 6SN7, I do not know if there is a European ECC-** equivalent for the 8V tubes
Tweak the circuit (resistance) values slightly, then you could use 12BH7A, 6GU7, 8GU7 and even 6350s, though the latter have a slightly different pinout.

/ed B in 73 degrees F (23C) sunny NC.

[EWBrown]

From my own experience, I've found very good consistency wih the "industrial" tubes, 5693 is good, as is 6189, they are very close in operating characteristics to 12AU7 / ECC82. 12AU7 is actually more of an RF tube, though it is very common usage in audio. I found from testing a few 6189s in the Poseidon and ST70 drivers (with CCS long tail) that the 6189s showed better matching between the two triode sections, than did random 12AU7s. I have not tried 5693s in that application.
6CG7/6FQ7 are also very good, but they have the 6.3 V filament connections to pins 4 and 5, and 9 is either unused, or an internal shield. The 6CG7/6FQ7 is the 9 pin miniature version of the 6SN7, whichis an excellent audio tube. There are also considerqably sions of the 6CG7/6FQ7 and 6SN7, I do not know if there is a European ECC-** equivalent for the 8V tubes
Tweak the circuit (resistance) values slightly, then you could use 12BH7A, 6GU7, 8GU7 and even 6350s, though the latter have a slightly different pinout.

/ed B in 73 degrees F (23C) sunny NC.

[soundbrigade]

The amp is almost done (and has been the last 5 years ... ... so I have no intention of swapping the 5693/ECC82 for anything else. By the way the amp is Rosenblit's Grounded Grid.

[soundbrigade]

Came to think of it, ECC83/12AX7 isn't the sharpest indian in the elevator (*), but I saw in good ol' Glass Audio that equivalents like 5751, 6681, 7729 and other were "better" that the standard ones, even though they ought to be equivalent.

I guess a military or industrial tube (= specially made for military or industrial use) may be a) more mechanical stable, meaning that the grids and stuff inside the tubes are heavier supported - no vibrations/no microphony and b) are better matched.




(*) Talking about persons with limitied intellectual capacity you use terms like "he hasn't got all indians in the canoe". or "he's not the sharpest knife in the kitchen drawer" or "the lift don't go all the way up", etc. I have an annoying tendency to mblend all these expression.

[EWBrown]

5963 has a mu of 21, the 12AU7 / ECC82 / 6189 / 5814 / 6680, etc have a mu of 17, they are all "close enough" to work properly, without any circuit changes.
Also there are 7 and 9V filament versions, 7AU7 and 9AU7.

Many of the "industrial" tubes were designed for computer usage, in which they operate in on-off logic states, and can remain in a cutoff condition for extended periods of time.



Then there are more colloquial sayings: "not the brightest light on the Christmas tree", and "the elevator doesn't go all the way to the top floor", and in really bad cases "the lights are on, but nobody is home"

/ed B

[Blair]

The 5963 is not bad at all, but VERY microphonic!! I have a few of them here and every one of them is microphonic to the point that dampers don't really help.

Blair

[kheper]

Speaking of the 5963, it has a max voltage rating of 250, not 300 as with the 12au7. 5963 RCA Clear Tops can be had for cheap on ebay, sometimes. I use them in the ST-70. They sound precise, rather than lively as some 12au7s do.

[Impmon]

The 5963 is not bad at all, but VERY microphonic!! I have a few of them here and every one of them is microphonic to the point that dampers don't really help.

Blair

You got stuck with some bad ones. 5963s are "computer" tubes, used to implement logic circuits, and you definitely don't want microphonic tubes in that application, sending false trigger signals to some other logic gates. That's even worse than the pops and crackles from microphonic TV tuner VTs whenever you change channels with those old timey click, click, click tuners.

[EWBrown]

I haven't seen any microphonic 5963s, yet, those I've tried are virtually noiseless.
I have had issues with microphonic WE396As, but then I discovered that they were oscillating at RF and using grid and plate stopper resistors (220 ohms and 47 ohms, respectively, cured the problem. Also, in SRPP usage, the filaments should be "biased" at 1/4 B+ voltage, that equalizes the absolute potential difference between the two cathodes, thissignificantly reduces any noise and hum issues.

I've also experienced some microphonic issues with 12AT7s, I just swapped them out with quieter ones.
/ed B