Can you tell something about these different GE 12ax7's (+tungsram el84) Pics

[Mit]

Just received these 5 GE 12ax7's. And one nos Tungsram el84.

I'd like to know if anyone can tell me anything about the GE's. Can you recognise which ones I have. Are they considered good/bad, characteristics etc. What is 12ax7A?

I appear to have 3 types (out of 5). The color of the plate is lighter / more grey in reality than on pics.

Firstly 1 of these: Called 12ax7A. Short-plate. Color of plate is not as dark as on pic though slighly darker than other 4 tubes. Getter is round. The insulating spacer is thicker than the others. Extra code: 78-48 188-5

Then 2 of these: 12ax7. Short-plate. Apart from color, the plate looks the same as picture above. Getter is round. (Seems to have no extra code or unreadable)

Then 2 of these: 12ax7. Long-plate (17mm). Plate is different then the ones above. D-getter. Extra code: 57-82 188-4 and unreadable on the other tube.

And for fun the Tungsram el 84:

 

[Mit]

1st pic shows the plates from the side, not upfront. It looks the same as the 2nd pic, just a bit darker.

Maybe I can describe it if something's not clear, th pics are no all that good.

 

[cap47]

12AX7A is low noise equivalent to 7025.

 

[DaveKS]

The one say has a 57-82 code, 57 is year but 82 doesn't make sense, that string is week of production, there are only 52 weeks in a year. Blowing it up almost looks like a 20 to me.

All the 188-4or5 indicated production Owensboro, KY plant. You don't see a whole lot of 188-4.

The others are 1978 short plates. The older 1957 long plate if still strong and not microphonic will probably be the shining star tone wise.

 

[Mit]

Hey, cool info guys! Starting to understand what I have here, I'm a beginner tube-wise.

You're right dave, I somehow made a mistake, it says 57-26.
I have two of those long plate's, no idea if the other one is a 57 but it looks the same. I can only make out 188 on that one.

If they are still in good working order I think I got a pretty good deal. Got them used from an audio-guy. He says they "still test good". For 15 euro for the five.

 

[Mit]

First I tried the '57 longplate in my bugera v5 combo. Honestly it sounded about the same as the stock tube to me. Then I put in a short plate and the tone got definately brighter, clearer, more top end, what I needed.

Then I put in the tungsram el84 and it rattled like crazy. I'm not sure if this can be considered a faulty tube or not (if you have comments on that please see my other thread).

 

[DaveKS]

Well the "tested good" comment can cover a wide range. In little simple emission testers if you look pics of meters on them you'll see good range goes from 65%-100%. So technically a tube that tests 70% could be good, but that's ready for trash bin to me. Good ANOS should test 90% or higher. 85% is my cut off point.

Next time you talk to guy, find out what tester he's using, he may not even be using a tester, but really for less than $4US per tube I would bet that he's not really doing anything other than sticking them in preamp/amp and seeing if sound comes out the other end.

But at that price you usually take your lumps and move on when you get duds. People who have and use real testers and do real screening will likely be charging at least double what you paid for vintage glass.

Be very cautious of buying power tubes from these types, a shorted tube tube can be bad news when takes out a fuse and worst case takes a resistor in your amp with it. I wouldn't.

 

[Mit]

Hmm yes haha. Thanks for the insight.

The main part of the deal was the nos tungsram and I got really unlucky with that. He won't replace it. I know "blue strat" may have his reservations (being a seller as well). I'm sure 99,5% of the time these tube are good but this tube is bad. I can't conlude any other way. (The sound minus the rattle is very sweet, but I can't use this tube #%¥£*).