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RE: OT: Thorsten, 2A3s, 45s and 300Bs.


I get a kick out of people comparing 45, 2A3 and 300B. Of course, with each type, we have differences.

Here I offer some explanation-- maybe this can help some of you a bit.

The common NOS 45's were built with decent plates, a decent grid set and a "W" or "M" filament configuration. Shaping the filament into a "W" or "M", while a cheap way to assemble tubes, creates all sorts of distortions and harmonics that ARE NOT THERE on the recording that is being played back. Despite this, some people like to listen to these tubes. What do they have going for them? FORCED to run LOWER PLATE CURRENT-- which GREATLY benefits output transformers! They are also EASY TO DRIVE-- which benefits the anp's driver stage operation.

The NOS 2A3 was built as a Single-Plate, and as a "biplate". The Single-Plate is rare, because it was too expensive to build for the Depression Era.... and was dropped from production. These were under RCA, FIVRE, CUNNINGHAM, etc. All were RCA. Raytheon also did a Single-Plate, but the construction was different. This is also rare. They sounded good, and were the most accurate reproducers of their day. Today, only EML has beaten them.

NOS 2A3 Biplates are a sandwich of two "45" plates, with appropriate grid and filament arrangements. There are two "W" or "M" type filaments in these, and they are connected together, as are the grids, and plate-sandwich.

They're powerful, reliable, euphonic, and have high distortion and timing-out-of-sequence problems. These sound good on non-revealing speakers, but sound trashy on transparent speakers. Today, cheapo tube makers still make them. Chinese varieties of these are even much worse. The best-sounding of the NOS Biplates are of old Sylvania manufacture-- with Spring-Tops tensioning the filaments. You will often find these in old Philco and Silvertone (Sears) boxes.

The 300B started life at Western Electric, and was a higher-power version of the W.E. 275 telephone repeater amplifier. They were fair-sounding, having a decent vacuum and decent materials. The "M" or "W" style filament structure created hot-spots in their radiation pattern, rendering them useless for accurate musical reproduction. The CHEAP filament system was used because these were designed for telephone-repeaters, not for the ultimate in High-Fidelity. Copies abound and they're generally even worse musically. The W.E. are more reliable than the copies.

Modern EML 45, 2A3 and 300B are all the SAME kind of tube-- all built correctly. Arguing over which one of THESE is best is pointless-- all are better than any of the other parts in your amp. Of course, the DICTUM still applies-- the lower plate currents sound best.

Some people prefer the "45" even in the case of EML-- all they are benefitting from here is being forced to run the lower plate current of the 45-- which is a GOOD THING! Actually, THE best tube of all of this discussion is EML's 2A3 Mesh-- run at almost (just a little higher) "45" specs.

---Dennis---



Edits: 07/15/12 07/15/12
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