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24.19.48.62
In Reply to: RE: EML vs. Sophia Meshplate 2A3 posted by tube wrangler on July 18, 2012 at 19:39:10
Also look into the startup transient voltages. Some amps - especially, some direct-coupled amps - drive the output tube grid positive during that transient, which is never good and the EMLs are especially sensitive to this. There are extensive comments on the EML web page - read them!
Since Dennis uses them and is a stickler for longevity, it's safe to assume his amps do not have this problem.
Follow Ups:
Hello Paul! Funny thing today-- coincidence? I've been working on irrigation systems today.
I have a guest here who has my whole system in his home State-- Wash.
He's developing a small stand-up coax. speaker-- an 8", and wished to use my shops and in general, get some development work done. He's got a great lady with him who is a master carpenter!
Well, I just came in-- soaked and muddy. They were on the Emissions Lab website! Looking at using the 5U4G they make-- maybe. It's a Mesh.
I took another look at it-- I've looked before. Today, I re-read the cautions about transformer DCR-- and other items on their website.
As you no doubt know-- I have the greatest respect for these guys who make these great Mesh-Plate tubes for us. I almost consider it a privilege to be able to buy them!
However, running a High-DCR primary transformer is a good way to get that soggy, syrupy, sweet old-fashioned sound-- NOT High Fidelity. Even worse, running high-henry, low-DCR chokes kind of deletes most of the fun that is in music.
And Cap-Input? Guys, please! I love your tubes- "smack"-- and I love you for making them-- but Cap-Input? NEVER!
Gotta have a choke on that rectifier-- even a little R.F. one-- something-- please! (I love the sound...other things too-- don't get me started!).
So how does one get those fabulous Mesh-Plate EMLs to live with me?
It isn't so bad-- I just soft-startup the power trans primary.
I want that device closed after warmup so the amp can get dynamic swings from the A.C. line. You can hear that, so a soft-startup device must be pretty well shorted after amp warmup.
---Dennis---
Well, Jac wants his tubes to live a long time. We want our amps to sound great. Fortunately those are not entirely conflicting desires ... :^)
But he does say, right at the beginning, it's the peak current through the rectifier that should be limited. A choke at the input is one way to do that, if it's big enough.
So true! Necessity, however, never sleeps!
---Dennis---
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