Mullard 12AX7 Reissue

[iknowjohnny]

I think he meant cathode follower, not PI.

[Bob-I]

If you ran it in the PI position in a D-clone and it survived, it's not an LPS. They croak with more than 30 or 40V on the cathode, not designed for anything but V1 really, I think.

That hasn't been my experience. I'm running LPS' in the PI 2 of my main amps for at least 2 years now without a failure.

The Mullard's I bought look like the LPS but don't sound the same at all. The Mullard has more lows and low mids than the LPS and they seem to have a tad less gain as well.

[ToneMerc]

If you ran it in the PI position in a D-clone and it survived, it's not an LPS. They croak with more than 30 or 40V on the cathode, not designed for anything but V1 really, I think.

It's the Tung-Sol reissue that can have this problem, not necessary the Sovtek LPS in a Dumble application. IMHO, you have to keep the tube in context with the exact application. I have built three Dumble like amps and I've had no failures. However, when I built a Dumblelator and my recent JTM45, I chose not you use the LPS in the CF position.


YMMV

TM

[David Root]

CF for sure too, but when I bought the two LPS I have from Lord Valve he counseled not to use them in any application that exceeded 30V on the cathode as he said they would poop out.

I did briefly put one in a PI at ~50V Vk and it didn't immediately pop, but I decided not to push my luck.

This was right after they were released some years ago. Perhaps they were toughened up after that?

Funnily enough I have used a Tungsol RI 12AX7 in a Marshall type CF at ~200V Vk without poop out.

[iknowjohnny]

I think i read the LPS has the same problem as the tung sol, but again, NOT in the PI, but in the CF position. The PI should be no different than any other gain stage as far as this issue.
Anyways, the Mullard RI has a sound thats similar to the tung sol in that they both have an extrordinary degree of harmonic complexity compared to other current prod tubes. they sound very different, but in that way they both deliver. i prefer the mullard RI and even if i didn't, 3 out of 4 failures with the tung sol put me off of them for good. I should mention however when i say "failures" i don't mean they died, but 3 of 4 had the loud hum that many tung sol customers have complained of. Oddly, the mullard RI also has a hum issue which seems to be with all of them, but it's not a issue unless your run more than 1 in the amp because the hum is very low if you run just 1. It's cumulative and if you run say 3 of them like i tried, the hum may be problematic depending on your ability to deal with it. But like i said, i find it only takes one in V1 and any more than that doesn't sound good to me anyways, so the hum is not an issue for me.

[dehughes]

Is the consensus, then, that the Mullard RI is fine in the V2 spot in a JTM-45? I'd like to try one in that spot, but don't want to cook it....

[selloutrr]

it's fine

[Colossal]

I was under the impression that the LPS was one of the tubes specifically reccomended for the PI.

Yes, Dr. Z uses the LPS in the PI position in some of his builds. I have one in a Rocket type build and am pleased with it. Nicely balanced.

David Root, 30-40V on the cathode for the Mullard reissues??. I have them in a client's Marshall build in V1-V3 and they seem to be tolerating the abuse and sound quite good. The cathode follower cathode is seeing some high voltage and surviving so far (fingers crossed).