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In Reply to: RE: 2A3 Options posted by 91derlust on December 22, 2016 at 12:30:02
Do us all a favor, and ask Jac what his favorite dissipation level is on his EML 2A3s, where it lasts long and sounds good to him.
I will be surprised if its 15 Watts plate dissipation. At such high dissipations, near the maximum dissipation rating, the 2A3 always sounds stressed there, because they are stressed, thermally stressed.
Post up here his response.
If anyone has to run the 2A3 that hard, for it to sound good, a DIYer likely has multiple problems elsewhere in his DIY gem / amp, typically in this order, power supply, wiring, layout, parts choices.
Be cool to hear Jac's response. Jeff Medwin
Follow Ups:
It's loafing, should last a good long time, and sound pretty darn nice at 15W. If it doesn't, the recommended use and 28W rating would be misleading.
I'm well aware of how Jac likes his tubes used - I've communicated with him several times and he outlines it on the EML site. I wouldn't be suggesting it if I did not have some understanding. For example, I would not run the 17W 2A3-M at 15W... more like 10W.Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Edits: 12/23/16 12/23/16
So it looks like there are a couple choices of 2A3 for 'high power' (two watts or so) operation. This is good news as I intend to re-build my DIY-HIFI Supply 'Billies" which already accommodate the 2.5V mesh plate 300B's from China (microphonic). WE-300B's from Kansas are getting to be close to 15 years old and have no getter left but still play well.
Link below:
According to Dennis Fraker, any 2A3 from China is inferior, "trash", due to poor metallurgy. It MAY possibly sound OK when new, but it will soon turn to trash over time, due to poor metallurgy.
The best two 2A3s to use are the JJ 2A3-40, and the EMLs, period.
The JJ is, by far, the best value of the two, and what Dennis designs for and supplies in his 2A3 amps in 2016. He ran JJs at RMAF this year, see Herbie Reichert's reviews for Stereophile, of his listening experience.
Jeff
I didn't say that it USED them.
The early TJ Globe 300B's were micro-phonic, later ones not so much. I have an early pair but they have not been in the amps for about 12 years.
"The JJ ...and what Dennis designs for and supplies in his 2A3 amps in 2016."To clarify, Dennis prefers EML 2A3-M for best sonics. Read down to the last couple of paras of the attached link.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Edits: 12/23/16
Yes, I was fully aware of that post. Here is a link to "the" most recent regarding this discussion.
Merry Christmas !!
Jeff
A person could make themselves dizzy tying to follow... Thankfully, I have (only) a passing curiosity.
Have a great Christmas Jeff!
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Dennis said " First of all, most NOS 45's, 2A3, 300B, etc., have a rectangular
plate structure, and usually a rectangular grid structure.
So far, so good. Now, what happens when we insert a non-symmetrical
part into this desirable arrangement-- we place into it a filament structure that is made like a cheap toaster-- a folded-up filament
mess that is "M" or "W" shaped. "
My question is,
What is the shape of the electron cloud?
Just because the filament is "a non-symmetrical part" doesn't mean the cloud is "non-symmetrical" and keep in mind the electrons do not go from the filament to the plate. They go from the electron cloud to the plate.
If the electron cloud fills the space between the filament and the grid in an even way then the fact that the filament is "a non-symmetrical
part" won't matter.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The point that is fundamentally misunderstood by many is that the filament shape determines the effective anode area.
dave
It is my understanding the coated filament of the 45, 2a3 and 300b produces a much more generous electron cloud than that of a thoriated tungsten filament.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The article I pulled those from was from 1929 which is the era of the 50.
dave
Page 11 shows the "M" filament of a 211 utilizing almost the entire plate.It's to bad that the book doesn't show the "effective anode area" for a coated filament tube.
Thanks for the link.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 12/25/16
I think we may be interjecting a bit too much into the accuracy of the sketches. It does appear clear that the anode area is directly related to the filament structure. In the drawings I referenced there are curves around the corner which seems slightly more plausible than the sharp angles shown for the 211. I do strongly suspect that the edges are much more softly defined and and the "boxiness" of the drawings represents the average behavior over an area.
The point I was trying to put forth was that the filament appears to define the "active" plate area and while 100% "anode activity" may be achievable, I am not convinced it is a figure of merit that we should solely base out tube choice decisions on.
dave
Can't help but suggest a serious consideration as to why some of us prefer the sound of 'round plated' tubes?
well.... since you are asking for wild ass hypothesis...
a typical "box plate" is planar about the cathode and has a grid and plate structure on either side effectively creating two distinct tubes in parallel. The Cylindrical model doesn't have the two discrete structures but a single one.
Now one can argue that in the planes in the "box plate" versions may (can) not be perfectly parallel leading to differing characteristics along the planes surface and the same goes true for the cylindrical version but the big difference I see is that the box plate model still has two distinct structures when viewed from the top and the cylindrical model will only have gradual change over the surface.
dave
;-)
A lot of these arguments fall apart for this very reason. The biplate 2A3 is bad because it is essentially two discrete tubes in parallel like the 152TL. By that same logic, the 45 is bad because it is also two tubes in parallel. The thing that finally sold me on this was comparing the EC8010 to the EC 8020. Both have the same Mu but the EC8020 has double the gm which translates to 1/2 the Rp. If you look at the tubes the EC8010 is simply an EC8020 with only one plate rather than a plate on either side of the cathode / grid structure so it can be argured that the EC8020 is simply a pair of EC8010's in parallel :-)
dave
Nice Dave, Nice.
Jeff, with an EIMAC 35T on my desk as I type this.
"I am not convinced it is a figure of merit that we should solely base out tube choice decisions on."
I agree and was just trying to point out that the electron cloud is much larger than the filament itself.
Some seem to think that the filament itself needs to cover the whole plate area or the tube won't sound good (or something like that).
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Thanks for the Christmas wishes!! It means something to me now-a-days.
I got saved, at a local Southern Baptist church in September 2015, so this, at my age, is only my second Christmas as a true believer in Christ.
Amen Bro'.
Jeff Medwin
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