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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
larryi
4,080 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.
charles1dad's avatar
charles1dad
10,250 posts
 
Onemug,That`s excellent news!I`m glad you took the chance and it worked out.I`d like to try these EML meshplates someday.Wished we lived near one another and could swap these with the Takatsuki 300b.
Regards,
onemug OP
784 posts
 
Charles, Thanks. Agree, a closer proximity would be nice.

Having 3 systems and having to pick one as your favorite is like having 3 children and picking the best. You could say one child has "achieved" more and that is what I would say about my bi-amp/active crossover system.

With the EML meshes top and bottom, this system has achieved the highest level of enjoyment so far but I still love my other 2 kids. :-)

A tricky thing with bi-amping is getting the "blend" right. I read all over the net about "I use a behemoth ss amp for the woofer and a sweet tube amp for the tweeter". No doubt that system would have a great low end and top end. I would question the middle though, where you are hearing ss and tube producing the same frequencies at the same time (x/o point and its slopes) but if it makes you happy, that's all that counts.
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