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In Reply to: RE: Dennis talks 2A3... post-RMAF 2016 posted by dave slagle on December 25, 2016 at 09:23:26
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: 12/25/16Follow Ups:
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"
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