A weak RCA 12AX7A vs. new production

2tones

Member
Messages
34
Tried a little experiment. Took a weak testing RCA 12AX7A (32/36 min 32) and compared it to several new production tubes in V1 of a silverface Vibro Champ. Even at close to the end of it's life, the RCA seemed to have more clarity than a JJ, GT (Russia), or Ruby (China) that was fresh out of the box.

Kind of goes against what I was expecting from a weak tube. Or is a weak preamp tube less noticeable than a weak output tube?
 

Lonely Raven

Member
Messages
1,003
Nope, just as noticeable.

This experiment speaks volumes.

Agreed. The output on many of these new tubes are surprisingly low. I was testing some new EH on my tube tester, just to get a reference point when compared to older tubes...and I was shocked to find that the EH tested just as week as used vintage tubes! :jo

Most of the JJ tubes I had tested way over most everything else.
 

Blue Strat

Member
Messages
30,722
Agreed. The output on many of these new tubes are surprisingly low. I was testing some new EH on my tube tester, just to get a reference point when compared to older tubes...and I was shocked to find that the EH tested just as week as used vintage tubes! :jo

Most of the JJ tubes I had tested way over most everything else.

I gave up on JJ ECC83s a few years ago when I got a batch of 100 and more than half were WAY below anything else.
 

Swarty

Member
Messages
1,130
I've had bad experiences with JJ preamp tubes also. I've had a couple dead or noisey amps come in for servicing and the problem was a bad preamp tube and each case the owner said he had just replaced the preamp tubes and in each case it was JJs. They also seem to be quite dark sounding. FWIW, I think their power tubes are among the best (current production).
 

recto-robbie

Member
Messages
2,322
I havent had any bad luck with the jjecc83s but on the other hand those RCA 12ax7a's have become some of my favorite NOS tubes I have found.
Ive had better luck with those JJ's when using them with an overly bright amp like my stiletto deuce I used to own.
Theres just something about those RCA's though. They add warmth and smoothness. I like them a lot and always keep at least one in my amp all the time.
 

Guinness Lad

Member
Messages
15,853
I ordered some KT77's from Bob Pleka last week and they kick butt. While I had Bob on the phone I asked him when JJ was going to make a better 12ax7, I said something that sounds like an old RCA. Basically, it's not going to happen. I do agree their Power tubes, EL84, 6V6 and KT77 are really nice but their preamp tubes need work, actually all new production preamp tubes are lacking.

I have 14 or 15 RCA's which I love but I will tell you if I load up my whole amp with them they sometimes become too much of a good thing.
 




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