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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
charles1dad's avatar
charles1dad
10,250 posts
 
Hi Onemug,
I hope these mesh plate 300b work out well for you.If that`s the case I`d be interested to read your impressions.I`ve not heard this particular tube but it has a very good reputation for excellent sound quality.This is a true mesh plate design as opposed to a'perforated' plate copy.
Regards,
onemug OP
784 posts
 
Al, thanks so much. I take responsibility for whatever happens but armed with your knowledge it feels pretty safe.

Charles, will do.
isochronism
2,893 posts
 
Hi Onemug,
I always agree with Al's and Charles's opinions wholeheartedly.
I am also a devote of the 300b as is Charles, and with his take on his Tak's, I believe!!
I currently use a pair of RP's with a secondary pair in the waiting as I got a nice deal on a quad set.
Starting fresh, I would go with your choice of EML true Mesh Plate. Very interesting.
I also have a pair of 45 amps which need more immediate attention on power tube replacement. EML is where I will go.
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.
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