Why are older tubes so much sought after

if you speak to many manufacturers of tube amps, tube cd players and tube preamps, in production today, you will be told that replacing the tube with nos varieties will have a mimimal sonic effect. bat and mcintosh are two examples of this.

i have found that many current poroduction tube components are relatively insensitive to changes in tubes.

Mrtennis, all I can say in response to your last post is, bullshit!

Every single tube component from my stable as well as those that I owned in the past benefited from tube rolling. Selected NOS tubes were always my preferences. There ar some nice new stock tubes like JJ or GE 211 among few others but in general, NOS rules. Only my opinion.

P.S
I spoke to more then few designers and in all cases the NOS were recommended and prefered over the new stock. Lowering the production costs and difficulties in finding the right source are just some of the reasons to choose new stock over NOS.

Well designed electronics OUGHT TO BE insensitive to minor variations of components, including tubes. Perhaps this design objective is not met in some audio equipment. All things equal, an old tube should be inferior to a new one because of gas infiltration over time. Maybe gassy tubes sound good...more of that tube sound.

My guess is that, when tubes were used in everything, there were a lot of manufacturers competing, and this competition resulted in superior product. Also, we tend to now collect and praise the very best of the old lot, and in that sense, older tubes have been cherry-picked (the crap models having long ago been trashed).

In some cases, key elements are just no longer manufactured, either because the scale of manufacturing is no longer there, or the product is now deemed hazardous. There is some speculation that the Chinese have recently stopped manufacturing the 845 tube because they were relying on old stock of Thoriated Tungsten filaments that are no longer available. I have also heard that key parts of the currently manufactured Western Electric tubes are also "old stock" and manufacturing will cease when those parts run out.

Some preference for old tubes is just a matter of personal taste and system matching. For example, a lot of people covet red-base 5692s. In my system, and for my taste, they are NOT right (I like Tungsol roundplate 6sn7s). The much larger variety of older tubes (again the result of ubiquity of tube use) means a greater chance of finding the right match amoung older varieties than the limited choices of new tubes.

I personally have found a few new tubes to be very good. I am a BIG fan of EML meshplate 2a3s. These are the best sounding 2a3s I've heard, though they MUST be driven gently to survive.

As for the comment above that well designed components ought to be insensitive to variations in tubes, that make so sense at all. With good equipment, minor differences in any component, including tubes, SHOULD be discernable --if you can't hear the difference it is because detail is being lost in the muddle of crappy reproduction.

Also, the suggestion that people who like old tubes might be enjoying "gassy" tubes is completely unsupported. Where is the evidence that all older tubes are gassier than new tubes because of infiltration? Sure, some may go bad over time, but, on what basis does one conclude that those are the ones coveted by those who favor older varieties? I have a tube tester that measures for this condition. The older tubes I use are NOT gassy. As far as 6sn7s are concerned, it is actually some currently manufactured 6sn7 that measure as gassy.