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

Post Subject: Hmmm, let me try this one again...Posted by floobydust on: 1/26/2009

Gee, now that I read my post again after yours.... that last bit didn't quite say what I was wanting to say (I hate when that happens). I was really referring to people being "brand specific" as my example of the 45 showed that you can't always go on what's printed on the base or glass as manufacturers frequently cross-sourced. So to simply state that a specific brand sounds best may not be an accurate statement.

I do agree that the internal structure makes a big difference... but, if the tube specs properly and has adequate immunity to mechanical induced interference, then you should not be able to discern any major difference in sound quality, at least not in well made NOS tubes as the industry had the same technology, materials and processes. If you look at almost any ST-glass 45, the plate, grid structure and filament is virtually identical. What varies is the mechanical structure that hold the pieces in place and supports the filament wires. There are also some differences in how they are "damped" to the glass envelope. The alignment accuracy also can vary depending on many factors from factory to factory. A more robust internal structure should hold up better over time against the internal forces at work, like the heating and cooling cycles over use and the forces exerted upon the tube elements from high current flow during normal usage.

This is why I've narrowed down my choices to a specific set of internal constructions for both 45 and 2A3 DHTs. It's also clear that Sylvania made the bulk of these higher quality versions (45 and 2A3). The Sylvania 5V4G on the other hand is not on my list while the RCA version is... again, it's the difference in the internal structure, and RCA had several changes over time.... generally not for the good as time went on.

The down side is that I don't have any pics with me as I'm in Germany till March... and my collection is in the States. I did do a few ebay searches and found one of the later RCA style here that is marked on the base as a Sylvania:

http://cgi.ebay.com/One-Awesome-SYLVANIA-2A3-Direct-Heat-Triode-Power-Tube_W0QQitemZ110341238567QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item110341238567&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A1|294%3A50

Here's a real Sylvania with the fishing rod top supports, they also have an additional vertical support on one side out from the anode structure:

http://cgi.ebay.com/Pair-of-Mint-Vintage-Sylvania-2A3-Tubes-Matched-Set-NR_W0QQitemZ250363760265QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item250363760265&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A2|294%3A50

Finally, here's the same thing with the coil spring supports:

http://cgi.ebay.com/Mint-Vintage-Sylvania-Engraved-Base-2A3-Tube-NR-Extra-1_W0QQitemZ260352917871QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item260352917871&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A2|294%3A50

I realize these pics won't be around for long... hopefully long enough. I'll make it a point to get some decent pics to post permanently once I get back.

In any case, you can see the difference in the older Sylvania dual-section 2A3 which uses a single anode structure. Better supports in general than the RCA and they measure better, perform better and I would easily suspect would last longer and be more reliable.

Regards, KM

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