GoodSoundClub - Romy the Cat's Audio Site

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

Post Subject: Interesting analogyPosted by floobydust on: 1/26/2009

Thanks Adrian,

Have you also had a chance to listen to some NOS 2A3? I'd be interested to see how they compare to the new issues. I've managed to collect quite a number of NOS 2A3 tubes over the years, brands I have include RCA, Sylvania, Philco, Ken-Rad and Zenith. In most cases, Zenith tubes were sourced from Sylvania (remember that RCA was the enemy... they also made TVs). I'm prettysure Philco sourced from both RCA and Sylvania and I'm not completely certain Tung-Sol made any 2A3 tubes, at least I've never seen one to date (but that doesn't prove squat).

In any case, the last version of the RCA 2A3 is only fair at best.... many cost reductions... and it shows. Overall, there are only two variations of the American made NOS 2A3 I actually like, both made by Sylvania and both are dual-section with a common anode structure. The earlier one has four coil springs on the top mica as filament supports. The anode structure is quite robust, heavily spot-welded and has thick vertical wire supports which are riveted to thick mica supports. They also have tension wires from the top mica to the glass. The latter version was the same but the four coil springs were replaced with four "fishing rod" support wires.

One other intersting brand was the Ken-Rad, usually in smoked glass. These are generally excellent as well, are true dual triodes (separate anodes) which are paralleled. It's tough to see this due to the smoked glass and these usually have a "fishing rod" filament support arrangement on the top mica. These are difficult to come by... I have one pair which is very nice.

I'm sure there are some other ones out there as well.... I have a quartet that are marked as are in Sylvania green boxes... but these really look funky inside... they look similar to the latter RCA versions but the plates are an funny color that looked stained. All four display odd colors... bluish-green on the top mica when operating and changing patterns with changing current. They seem to spec okay, but they are just plain odd.... they don't sound good either.

In any case, I'm not a huge beleiver in the fact that certain brands have a certain sonic signature. Even moreso when you consider the fact that tube manufacturers frequently sourced from each other due to the sheer cost of gearing up the line for a particular tube type. I also have a perfect example of this... a pair of RCA 45 NOS tubes with matching date codes on the bases and in identical boxes... truly new. Problem is, one is an authentic RCA made 45 (which I don't really like) and the other is most definitely a Sylvania made 45. The internal structure gives it away. In my not so humble view, if the tube adheres to it's specifications tightly, has low-noise, good insulation from the heater-to-cathode (IHT types) and is immune to mechanical excitation, there is little to prevent it from sounding clean and neutral. I have measured some differences in distortion with certain brands which is consistent, but if they bias the same and have no mechanical issues then there should not be any real sonic difference.

Regards, KM

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