12AX7's Long Plate vs. Short Plate + Need a test plan

Jim C · #1 12-29-2010, 07:54 AM

Been a while since I've done any tube rolling and thought I'd experiment over the weekend. In the past I have generally liked the sound of old Mullards more so than Groove Tube, Sovtek, RCA branded units made in Yugoslavia, Raytheon (Japan), & NOS Nationals & Sylvania's.
This go round I also have some old Phillips (US), Dynaco W. Germany (possibly Telefunken?) and Amperex tubes.
The reality is that their are just too many to choose from before sonic fatigue and boredom sets in.

Pretty sure that I may have the same brand of tube both in long plate and short plate variants. As I recall, the audiophiles liked the long plate's better although I'm not sure what was "better" about it.

I'm looking to you guys for opinions and perhaps a test plan as to a decent way to start this process.
Amp in question is a Mesa Walkabout (reported to be responsive to tube swaps) that uses 1 tube in the preamp stage and 1 tube to drive the Mosfet power section.

BuzzKing · #2 12-29-2010, 09:35 AM

I am certainly no tube expert. I went through this exercise a few years ago. I bought a bunch of tubes and just let my ears tell me what I liked. Here are some resources that I used:

Talkbass Thread: 12AX7 bass preamp tubes Favorites and Lifespan

Joe's Tube Lore: http://www.audioasylum.com/audio/faq/joes-tubes.html

IIRC, I ended up with Westinghouse Long Plate in my Fender TBP-1, JJ short plate in my Eden WT-600, and Sovtek in my Aguilar DB659.

BK

twinfallsbass · #3 12-29-2010, 10:57 AM

I opened a thread about this very same topic a while ago, do a search and you will find a bunch of info about this. I do know that long plate 12ax7's are supposed to be more prone to microphonics, but people also say they sound better and are more sought after as well. I personally use Telefunken and Amperex in my amps

BurningSkies · #4 12-29-2010, 11:23 AM

A ways back I got a batch of Ei tubes (no longer made

) and it was interesting, because even though they were sold as the 'same' 12AX7 they showed up in both long plate and short plate versions, as well as smooth versus non-smooth plate. I found that I could not tell the difference from long/short plate in an amp. The real trick with Ei's was that they had a high failure rate right out of the box, so you had to buy a bunch just to get a couple that weren't microphonic...but the good ones sounded REALLY good to my ears.

I also have some vintage Mullards (which sound good in my 65 vibrochamp), RCA black plate, Sylvania, and a few unmarked vintage tubes as well as EH, etc. I really find that old tubes sound great in old amps, modern amps seem to be tuned to modern tubes and using some of the vintage tubes in them leave them sounding soft, undefined and dark to me.

CopperheadLXXIX · #5 12-29-2010, 11:26 AM

I can only speak for one brand, but I tried the JJ Gold Pin both short & long plate in my Marshall MB450. Both sounded really good, but I found the long plate to be deeper in the bass. In fact, so much so that when on the tube/classic channel, even with the bass knob turned all the way down there seems to be little to no low end attenunation.

steamthief · #6 12-29-2010, 11:31 AM

I tried a bunch of brands of NOS valves in my TB-600 and the Telefunkens sounded SO much better than all the others, it wasn't even close.

Seans · #7 12-29-2010, 01:02 PM

Mullards and Telefunken always seem to come out best, I did a test with Mullards and Brimars, I had approx 20 mullards and 5 Brimars. All results came back with a top 5 which were astonishing and I mean awesome, the next 10 were great sounding and the last 10 were just good, but way ahead of the normal cooking valves like our new ones available today.
The results, the 5 best ( and I still use these today) were all Mullard short plate, the next 10 were a couple of long Mullards and the rest short mullards and the last 10 were long Mullards and the Brimars.
The 20 Mullards/Brimars, I gave to a HiFi mad friend and said find me 3 of the best of this bunch, 3 Mullard Long plates came back.
I think HiFi is all about the whole spectrum the soundstage, the overall, with Guitars and Bass its more the frequencies or the certain ones that we look for, and the long plates just didn't quite do it for me.

Jim C · #8 12-29-2010, 03:54 PM

Quote:

Originally Posted by BuzzKing

I am certainly no tube expert. I went through this exercise a few years ago. I bought a bunch of tubes and just let my ears tell me what I liked. Here are some resources that I used:

Talkbass Thread: 12AX7 bass preamp tubes Favorites and Lifespan

Joe's Tube Lore: http://www.audioasylum.com/audio/faq/joes-tubes.html

IIRC, I ended up with Westinghouse Long Plate in my Fender TBP-1, JJ short plate in my Eden WT-600, and Sovtek in my Aguilar DB659.

BK

Great thread; thanks to all who have offered wisdom on this issue. Am thinking I'll do this over a few days with Day 1 being the European heavy hitters and Day 2 challenging the winner of Day 1. Might spring for a JAN tube as it seems many do like these as well. Best part is that time spent on the front end of this test will pay off in the long run as these tubes have such a long life span when treated properly.
Any other thoughts or insights are greatly appreciated.

audiomitch · #9 12-29-2010, 04:07 PM

Quote:

Originally Posted by twinfallsbass

I do know that long plate 12ax7's are supposed to be more prone to microphonics,...

That's what I understood too. I was looking at some new production preamp tubes for my Fender Twin. The JJ ECC803s long plates weren't recommended for combo amps because of possible microphonics. I would imagine that the vibrations from a bass amp would be even more intense? I don't know that for a fact, though.