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In the Forum: Melquiades Amplifier
In the Thread: Single-stage Melquiades vs. DHT amps

Post Subject: Are NOS and new manufacture comparing oranges to oranges?Posted by floobydust on: 2/13/2009

Adrian,

Thanks for a most interesting post. I can't fully respond to this as I don't have the new tube brands you have. I posted earlier regarding my personal findings with the EML 45 solid-plate versus NOS however. Ultimately I found that my Sylvania made 45 NOS tubes to perform better and preferred them, especially in light of the mechanical sensitivity I experienced with the EMLs. The latter will certainly cause audible distortions induced from the sound itself modulating the internals. As a result I found the (known good) NOS 45 to provide a more neutral and accurate sound.

Some of your comments do cause me to wonder about some things... mainly the conditions of your tests. It's unclear (at least to me) what amplifier you are using as a test subject and what are the specifics regarding it. Things like circuit topology, biasing points, loading, driver stage details. In some cases, new amplifiers and/or DIY amplifiers have been customized for a specific tube. As I found previously the EML 45 needs additional bias current to perform it's best when compared to NOS 45 tubes. So if the amplifier used was biased specifically for the Kron 2A3 (just an example) then perhaps the NOS 2A3 was no longer running in an optimal setup. Of course, I'm only guessing here... but did you measure the operating points and performance of each tube in the amplifier or only listening tests? In my humble view, if you don't verify proper operation of each set of tubes, then the overall test is somewhat suspect.

I also have to question if many of the new manufactured tubes with old tube types (ala 45 and 2A3) even qualify as being a "true replacement" or is really a different design with "planned specification adherence" to the original. Case in point, I've read that a certain new 2A3 tube is identical to their 300B tube with a different filament voltage. I've also seen heavily extended ratings for some 2A3 tubes with plate dissipation well beyond 50% of the original. My case (again with the EML 45, as it's the only one I can truly comment on) makes it pretty clear that the new manufactured version is in no way, shape or form a true 45 DHT as there is nothing in common with the original right down to every internal component. Not to mean it's not a good tube, but to point out that is not a true version of the original.

Based on my experience with the EML 45, I would not be inclined to purchase a pair of their 2A3 tubes... but the Kron tube seems intriguing and I may look into their 2A3. In any case, again, thanks for the candid review/comparison. As for the 45... I couldn't possibly agree on selling my NOS versions for a pair of the new manufactured ones... no way!

Regards, KM

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