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Has anybody tried the new JJ Tesla ECC83S tubes yet as a replacement to stock OEM ones?

I want to replace the tubes in my recently-acquired ART Pro MPA mic preamp. The only experience I've had in "tube rolling" (as the audiophiles refer to it) is replacing the stock tubes in my VTL TL2.5 stereo preamp with NOS Mullard 12AT7's and 12AU7's. BIG difference! Tighter, punchier bass, lowered noise floor, more detail in the treble, overall it was a terrific cost-effective upgrade for my audio system.

I also replaced the motley collection of tubes in my Ampeg SVT 3 Pro Bass head with new Electro Harmonix tubes and enjoyed a quieter amplifer, with less crispy overdrive and cleaner output.

I was thinking of trying the new JJ Tesla's as they are supposed to be a modern copy of the revered Telefunken 12AX7's. I was wondering if anybody had an opinion on these tubes or perhaps on another brand that you tried and liked in your ART Pro MPA.



CoyoteTrax Tue, 09/20/2005 - 14:08

I like the Tesla/JJ's alot in my Pro VLA. I liked the stock tubes the the Tesla's are a little smoother with more dimension. Very quiet, and the highs are better represented I think.

If you like the Mullards I may have to give them a try just for the heck of it. I've been a fan of the Tesla ECC83S for a lot of gear though and they do very well in my Pro VLA.

Hawkeye Thu, 09/22/2005 - 07:48

I see some 12AU7's and 12AT7's suggested here. Using my limited understanding of these things, don't the AU's and AT tubes have a lot less gain than a 12AX7?

If so, is there sufficient overall gain in the preamplifier to make them useful without a corresponding increase in noise?

As it is, I've ordered a couple of the JJ Tesla ECC83S but am interested in understanding what the effects of these different specification tubes would be.

While I'm thinking about it the ART Pro MPA is specified with 12AX7A tubes. I'm substituting 12AX7's (without the "A" suffix).


CoyoteTrax Thu, 09/22/2005 - 08:36

Right. AT7's put out around 70% of the gain as AX's; and AU's around 50% I think. That's what helps change the tone so dramatically but at the same time reduces noise.

The Tesla/JJ's are 12AX7's, they're just called ECC83S's. So you're getting the same gain levels with them a 12AX7 gives you, but smoother and more balanced (IMO). More of an audiophile-type performance.

jonyoung Thu, 09/22/2005 - 11:37


I haven't had any trouble using 12AX7's instead of 12AX7A's. Any AX7 category tube has a gain factor of 100, the DF7's and AT7's are 70. They're much easier to use on vocals due to the lower gain. It's almost impossible to drive one into distortion, as well as being warmer sounding.

Hawkeye Thu, 09/22/2005 - 13:01

Good info JY. I can see what you're saying about the 12AT7. To back up your story from the bass world, players who use Traynor's new YBA-200 all tube bass head are saying that replacing the 12AX7 with a 12AT7 gives them the opportunity to play cleaner and louder before the circuit distorts because of the lower gain.

With the ART Pro, I plan to experiment tracking Elec Bass Guitar and don't mind if I can get some overdrive on the sound, so for now I'll stay with 12AX7's. My Focusrite Trakmaster give me a pretty clean DI bass sound. I'll see if the ART can give me something different. I think it will.