What tubes are best for an MP-2?

[Dante]

Yup, those are the ones I've seen - BTW: I am very close to Petaluma, CA - the home of Mesa, I see a lot of their gear (and ADA stuff) on craigslist

http://www.mesaboogie.com/tubes/pre-amp-tubes/SPAX7.html

[vansinn]

Research reveals the SPax7 to be Sovtek's or JJ's, tested for extra low noise and microphonics; else they're reportedly the same, though some of course say they sound better. as in cleaner then normal 12ax7's; who knows..
All using them seems to agree they are indeed lower noise, though I notice comments on whether or not they are less microphonic in nature.
They feature some sort of elastomer wrapped around them, likely being what reduces the microphonics.

[Harley Hexxe]

That's just labeled heat shrink tubing Sinn.

[vansinn]

That's just labeled heat shrink tubing Sinn.

Yeah, I should've referred correctly ;)
Question is if it has any effect on reducing microphonics?
I'm thinking that, in theory, the wrappings, due to having maybe some [elastomer-like mass], perhaps could act as a vibration dampener.. :dunno:

[Harley Hexxe]

Pure speculation here...

    It may be possible that the vibration may be dampened a little by it, but from what I've read in the description in the tube, they seem to suggest that the heat shrink tubing may also help augment the vacuum with the additional pressure from the outside of the bottle. But I'm not sure if I'm interpreting that correctly.

     Harley 8)

[rnolan]

Hard to say if the "condom" actually adds any value sonically, it sets them apart visually from the slightly cheaper STR 12AX7s and makes it's quite hard to view the internal construction of the tube. Probably helps with warm up speed and slower cool down  :dunno: .  Anyway they sound reasonable in an MP1 but not my tube of choice for the MP2.  In the MP2 they fart a bit and lack definition on the bottom E and are quite 2D.  When I swapped them out for the Mullard long plates it was like Ahhhh..... much more like it  :thumb-up:

[Harley Hexxe]

From the description you give Richard, it sounds like they are short plate tubes. and definitely not the choice I would want for the MP-2. Long plates seem to be much more agreeable for that preamp.
   Thanks for that review, that helps.

      Harley 8)

[MarshallJMP]

Pure speculation here...

    It may be possible that the vibration may be dampened a little by it, but from what I've read in the description in the tube, they seem to suggest that the heat shrink tubing may also help augment the vacuum with the additional pressure from the outside of the bottle. But I'm not sure if I'm interpreting that correctly.

     Harley 8)

That it could help a bit against microphonics, yes maybe somehow, but that it augments the vacuum that's really far fetched.

[vansinn]

Hard to say if the "condom" actually adds any value sonically...

It's a condome? Oh gosh, I gotta have an MP-2 with condomized tubes!
But wait! ADA prefers direct interfacing, so.. nope, I cannot condome the use of tubes in gift wrap..

[MarshallJMP]

so.. nope, I cannot condome the use of tubes in gift wrap..

Condome, hahaha great!

[Harley Hexxe]

Pure speculation here...

    It may be possible that the vibration may be dampened a little by it, but from what I've read in the description in the tube, they seem to suggest that the heat shrink tubing may also help augment the vacuum with the additional pressure from the outside of the bottle. But I'm not sure if I'm interpreting that correctly.

     Harley 8)

That it could help a bit against microphonics, yes maybe somehow, but that it augments the vacuum that's really far fetched.

     That seems to be the implication in the link Dante posted, but I agree with you. it sounds like bull :poop:

[rnolan]

Hey Harley, definitely short plates, the only visual difference with the STR 12AX7s and the SPAX7 (I have a bunch of each) seems to be the condom.  And I agree long plates seem the better option for the MP2.  That said though, the original short plate chinese bottles were great, albeit not quite as 3D as long plates.  One of my MP2s came with EH tubes, I found them very ordinary and changed them out asap.

[Harley Hexxe]

Richard,

    The original tubes in my MP-2's weren't short plates, they were in the middle kind of. In fact, I don't believe any of the ADA gear I have, ever had short plate tubes in them. They were all the same tubes.

[vansinn]

Now, don't go do this experiment, 'cause the MP-2 mains transformer can't supply enough juice..
Some years ago, I tried a 12BH7 quite long plate tube in pos #2, and had a really cool amp-like tone.
The 12BH7 is a low gain tube, so it worked with Voicing 8 only, as this one has the extra gain to compensate.

I refer this merely to add to the discussion on long plate tubes.
And remember: The tranny cannot really supply the extra 150 mA, going from the 12AX 300mA to the 12BH 450mA heaters.

[MarshallJMP]

The 12BH7 can't be used since it drawing double the heater current, (300mA vs 150 mA from a 12ax7) and the plate resistance is way to low which results in a µ of only 17.This baby needs current!!!