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Help with tube specs

I will be getting a pair of EML 300b "mesh pate" tubes in a few days.

EML warns that the meshes should be run between 22-28 watts of dissipation with the closer to 22 the better and 28 MAX.

The amp I will be using them in is fine but I have another amp I'm not sure of. It's a Welborne 300b DRD. I was able to find this much:

">>>I have a Welborne manual for the 300B DRD and there are no voltages given in the manual. However, the original owner wrote his voltages on the schematic after he built the amps. He shows 505V on the plate and 190V on the cathode for a plate voltage of 315V. He also shows a cathode current of 65mA. So that means you have a plate dissipation of 20.5W.<<<

I also got this:

" The 300b mesh will not tolerate 500v on the plate. Even with a reduced dissipation on the tube, the tube won't last!"

I also read that with the tube drawing 1.4 amps at 5 volts (7 watts) you would add this to the 20.5W for a total of 27.5W. At least that keeps me in the 22-28 realm.

Can anyone help me sift thru this info? Opinions as to "how safe" it would be would be appreciated.

In the meantime, I will only run it in the safe amp for warranty purposes but would eventually like to try it in the DRD and would hate to eat the money if it's a mismatch.

Thanks.
onemug
onemug OP
784 posts
 
Isochronism,

I love the 45 also. I had Fi 2a3 monos that could use the 45 with a rectifier sub but never felt I got the full experience of a true 45 amp. Right now I'm using another 2a3 amp that also can use the 45 tube but use this amp in an active x/o system for the tweeter and with it seeing only 2.8k and above, I don't hear much difference between the 2a3 and 45 so I just use the 2a3 in it.

I have a pair of almost NOS Tung-Sol 45's and a pair of Sophia Meshplate 45's that are gathering dust. If you ever think about letting go of your extra set of RP's, let me know and maybe I could use these 45's as a partial trade for them. I would dust them off first. :-)

btw, I did order a pair of the EML 2a3 meshes along with the 300b's meshes. I figure whatever the mesh does, might as well have the blend at the x/o be as good as possible.

I have tried using 2 300b amps in this bi-amp system (nice on paper having the same type amps) but the 2a3 (and 45) just do the highs better for me.

isochronism
2,893 posts
 
I recall in past posts of your general system set-up, which I always felt was excellent. In fact, I do plan to do similar as I have a pair of JBL 4550s with original HF driver/fiber horn etc, which I have had for years put away.
I am in a small apartment and will move someday and plan to also employ active xo. Your's must sound really nice!! The 45 amps came with TJs and RCA/Cunningham which I am currently using. The EML Globe limited looks very interesting.
I just switch back and forth from 300B to 45 amps every couple weeks. Sure do like them both. Using Beauhorn Virtuosos, btw.
isochronism
2,893 posts
 
Mesh on top and bottom!! Very nice indeed!!
I have heard/read nothing but good reports concerning EML.
larryi
4,033 posts
 
I run EML meshplate 2a3s in my Audionote Kageki amps. A friend runs meshplate 300bs. We have both found that the EML tubes are reasonably reliable and long lasting, but, they seem to be quite touchy about being pushed beyond specifications. When I tried the meshplates in a different amp (unknown dissipation and plate voltage), I got flashing on the plate and distortion after a few minutes of operation (conditions I did not experience with any other 2a3). I think that EMLs restrictions must be respected.

Operated properly, the meshplates are quite special. They deliver the most enveloping soundstage I have heard. If someone were to characterize this sound as "phasey," I can see why, except that image placement is very specific.

If you have any questions, I suggest contacting George Lenz at TubesUSA (US distributor of EML tubes). He is terrific when it comes to prompt replies and gives very good advice--he will not steer you wrong.
onemug OP
784 posts
 
Got my tubes. Put 4 hours on them yesterday and about the same today. They were great right out of the box and have continued to improve.

Larryi, I did get them from George. He was a pleasure to do business with.

I didn't expect any issues with my my main amp, I'm easily within the 22 watt dissipation. I went over this with George beforehand. I did get an email back from the Welborne site and they said the DRD was ran at 350 volts and 60 mA bias so that comes out to 21 watts dis. I should be fine if I choose to try them in there.
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