[rustneversleeps]

I bought a set of 4 EH 12AT7 as spare for my AVA 500 from VintageElectrons. They were tested barely in the good range on my Jackson tube tester.

I returned them and got a replacement set of 4 (I didn't mark the tubes before I returned them, so assuming that they sent me a different set, they claim they always check their defective returns with their equipment, also they said they check their tubes before they sent them out).

Anyways, the new replacement set tested the same, had only little life left in them, I ended up keep them because I don't want to keep paying for the return shipping fee.

My past experience with the EH 12AT7 is once they were barely into the "bad" range on my Jackson tube tester, and used in the AVA 500, there were noticeable high frequency roll off. And yes, I have some strong 12AT7 tubes to compare with.

My conclusion is eithter VintageElectrons bought a batch of bad EH 12AT7s, or that's how EH make their 12AT7s, only give it a little life, so you will just keep buying.

Oh, with that little life in the EH 12AT7, again from the past experience (I always check the tubes before I put them in the amp), they will last approx. a year, if the amp's being used once a week for about 5 hours, it works out to be about 265 service hours.

[Wayner]

I think Frank offers these tubes on his website. I'm pretty sure he checks them and makes sure they are matched sets. Might save you some money in the long run.

Wayner 

[avahifi]

We have only been using JJ 12AT7 and 12AX7 tubes for over 2 years now, and of course the Sovtec 6N1P tubes in newest Ultra and T8 preamp line sections and DACs.

Frank

[Listens2tubes]

Maybe it's time to clean the sockets and calibrate your Jackson.

[BrianM]

Maybe it's time to clean the sockets and calibrate your Jackson.

I was told it's better to "calibrate your Jackson" before you "clean the sockets."  Bada bing!

[martyo]

I was told it's better to "calibrate your Jackson" before you "clean the sockets."  Bada bing!

  Just what I needed this morning 

[aln]

Anyone try the gold pin JJ 12at7's? 

[mark funk]

JJ Gold pin 12AT7s. It is the same tube with gold pins! I don't think you need gold pin on a tube that may last two years maybe.

[rustneversleeps]

I can see why Frank got frustrated during the early days of his Audio Basic when some of the readers didn't read his publication carefully.

If some of you Bozos here read my post carefully, you would have noticed I said, I do have some strong tubes to compare with. I used the same tube tester to find bad tubes in the used Super Pas4i that I bought from Frank, Frank verified the tubes were bad with his scope and square wave generator, and gave me a new set.

So that means, some of you Bozos, neither the tube sockets need to be cleaned, or the Jackson needs to be calibrated. Oh, in case some of you Bozos don't know, the Jackson only has one tube and 1 cap inside that need to be replaced once every great while. Therefore, no calibration needed.

[Tom Alverson]

Hey Rusty:

What would you consider a good reading for  a 12AX7 on your Jacskson?  I have a Jackson Model 648a "Dynamic Tube Tester" and the meter shows 0 to 70% as "BAD" and 70 to 130% as "GOOD".  I'm testing the old Jolida tubes from my "vintage" Fet-valve stuff (the original Fet-Valve line) and they are looking pretty weak so far.

Tom

[rustneversleeps]

Anywhere from 90 to 110 is considered good, I think when it's above 130, it's considered "unknown". When I measured the 12ax7 in the Super Pas 4, they all read between 65 and 70. Frank put the tubes back in then fed a square wave through the inputs and measure the output with a scope, the gain was pretty low.  Frank put a new set of tube in and measured the gain again, and it was correct. Then I measured the new tubes with my Jackson 648, they all read about 95. My Jackson tube tester belonged to the president of a ham radio club in Ohio, it's in exetremely good condition, these guys know their tubes.

[Tom Alverson]

Rusty:

I tested all of  the 12ax7's I could find and here are the results:

Brand   Triode1   Triode2
Amperex Holland   85   92
Amperex West Germany   89   95
Amperex West Germany   98   100
Dynaco West Germany   97   104
Dynaco West Germany   111   112
Dynaco West Germany   110   111
Dynaco West Germany   112   111
Gold Aero Frosted   98   93
Gold Aero Frosted   95   99
Jolida   66   68
Jolida   55   76
Jolida   65   90
Jolida   56   79
Jolida   78   75
Jolida   75   85
Jolida   65   73
Jolida   60   85
Jolida   53   50
Jolida   44   35
Raytheon USA   82   82
RCA USA   94   95
RCA USA   65   75
Telefunken West Germany   98   119

The "Dynaco" tubes came out of an old stock factory assembled PAS-3 I have laying around.  The Jolida's are from all of my Fet-Valve stuff.  They measured the  worst, but they are over 15 years old and have  more  hours on them than any of the other tubes. 

Tom

[rustneversleeps]

I too, pulled my original dyna tube off my stock ST-70 and put them away, they are bugle boy and dynaco brand, they all measured up to about 100. I replaced them with EH EL34 tubes, they measure 80 to 85 new, just a little into the "good" area. I measured various new Electro-Harmonic tubes, they all measured low.

In your case, if the Jolida tubes have had 15 years of usage, maybe they should be measured low. In most cases, the good vintage tubes all measured from 90 to 110 on my Jackson.

[rustneversleeps]

The new Electro Harmonic 12AT7 measured 70 to 75, almost "bad".