SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ SET Asylum ]

---

[ Alert Moderator ]

---

RE: EML 2a3 mesh and JJ 2a3-40

Posted by tube wrangler (M) on July 11, 2012 at 12:21:44

In Reply to: RE: EML 2a3 mesh and JJ 2a3-40 posted by andy evans on July 11, 2012 at 11:22:03:

Let's put a little finer point on things, Andy.

(1) You can get JJ 2A3-40 in singles-- if you buy 4 or more-- for about $125 USD each.

(2) This tube is large and rugged. Run it at 12.5 watts total dissipation each. If using EML Mesh, run at 11.8, if running old AVVT Mesh, run at 10.5.

(3) NOS 2A3s. A FEW of NOS (old RCA Single-Plate, Sylvania Spring-Top Biplate) sound good on most music-- but not GREAT like EML Mesh.

The WORST of these old Biplates are RCAs-- which are just plain distorted. We used to toss 'em at trash cans. Also W.E. 300B tubes. I serviced many a theatre-- these always went into Dumpsters. The "M" and "W" shaped filaments (CHEAP! or it that CHEEPIE!?) that these, and most 45 tubes used made them sickenly euphonic and decidedly inaccurate music-wise.

The Studios all knew it-- not only did they trash the W.E. gear-- they got it OUT of their theatres, and put in ALTEC. That was a MONUMENTAL improvement!

Amps got better also. I actually ran some theatres from McIntosh KT-88) amps-- and did fine with them. Today, that's not so great with me-- but in those days, when you needed a reliable amp that sounded OK-- you could go with them, and run them for years. You STARTED with new capacitors, of course. The old electrolytics would be another trash-can item.

NOS Biplate 2A3s possess a kind of musical euphony-- but not as bad as one might think. These things were two 45 tubes sandwiched together, with appropriate filament, grid and other wiring changes.

This caused two things-- (1) they were not as transparent as the 45 because the tube now had a lot of junk in it-- we got more distortion and less transparency. (2) They LOST a lot of musical detail (compared to 45).... or a GOOD 2A3 (RCA Single-Plate at that time).

The problem was the same as with the 45-- the filament assembly was JUNK-- and still is. Had they built a welded, waterfall kind of filament structure like they had in their-- too expensive to produce-- Single-Plate RCA, the sandwich 2A3 and the 45 would have been accurate music reproducers. Well, they're NOT!

Today, the only output tubes made in the world that are actually built right are EML.

JJ 2A3-40 is an orphan-- also produced by the same people. The filament structure in the EML consists of vertically-hung, welded sections just like the old RCA Single Plate-- but better, and with far better modern materials. The filament structure, grid set, and plate all line-up with each other, and we get a uniform radiation pattern-- we don't have euphonic "hot" and "cold" spots messing with our music like the NOS tubes do!

The JJ is a well-engineered cheapie. The filament is long and strung-out just like a W.E. 300B, BUT it's not draped-in like a @##$%%Mart Toaster-- it doesn't form the DREADED "M" or "W" shape that RUINS MUSIC. Instead, they simply run the whole thing up and down and across the tube's top and bottom spacers, but they were smart enough to run some filament across both the top and bottom of the spacer plates-- and got---Tah Dah!!!---- VERTICAL filament strings. Now, the radiation pattern between this structure, and the plate is the SAME SHAPE-- and now the tube works! La, La! Music! Really!

What's wrong compared to the EML? Instead of 8 equal vertical filament sections welded onto bars at the top and bottom of the tube, we have only ONE long filament.

This ONE long filament means that one end of it is at 2.5 volts, the other end is at zero. All along the filament length, we have a different bias at any given point than at another given point. The radiation pattern is not totally uniform, but it's certainly better than mis-shaping the thing as well! The other thing is that the long filament can get looser easier-- but there are a few nice, thoughtful touches done to minimize that-- somewhat.

The tube is made from really good glass, is rugged, heavy and-- for the price-- a great performer.

Can it compete with PERFECT (almost!) filaments and a Mesh Window (EML)? Nope! But, then, it's only $125 bucks, and it lasts a long time, and sounds really good in a good amp.

What's not to like on the JJ 2A3-40? Nothing-- at the price.

---Dennis---

Edits: 07/11/12

This post is made possible by the generous support of people like you and our sponsors:

Parts Connexion

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---