Tube newbie question of the day: why are (good) older tubes better? There was a wider use of valves then, leading to more efficient production with economies of scale? The Lord Sauron stole the recipe?
Thank you for all this good advice - Ebay sounds a bit risky, though... still, in for a penny, in for a couple of hundred dollars.
Transistors came along. Then integrated circuits (IC's). Most (but not all) tubes became obsolete. That's why. In the 80's and 90's I spent some time working at a company that made some of the last remaining vacuum tubes on the planet, so I know a little about them. There aren't many people wandering the planet these days who can tell you much about tubes. The folks on Head-fi are probably one of the best remaining resources.
The recipe was lost, is probably a good analogy. More to the point, no one cared any more. The economies of scale just aren't there for a relatively small handful of audiophiles, who still want tubes. The Chinese and Russian folks who bought the rights to make Tung-Sol tubes for example, apparently didn't also buy some of the arcane knowledge that has since been lost to time.
The remaining tubes made today are for things like satellites, radar, etc, and they're insanely expensive. They also don't resemble audio tubes, but the general principle is the same.
When it comes to hand-made things like audio tubes (and the stuff I worked on), there a lot of things about the process that just weren't written down. The folks who really know what to do, retired, passed away, etc before documenting what they knew. Metallurgy was probably part of it, but that's surely not all of it. People become subject matter experts in their little parts of the world, that made pieces of this tube or that. For whatever reason, they chose not to share what they knew before they moved on. Speaking from direct experience, I know that there are undocumented parts of the process. Sadly this is true in a lot of fields where manufacturing is involved.
Today, I am a big fan of documenting things that haven't been written down, and this is one of the reasons why. Any time there is too much "Tribal knowledge" involved in any process, the company making (whatever it is) loses out when the folks who don't document what they know, leave the company, retire, die in a car accident, etc. It doesn't help when the technology you're working on becomes obsolete. People and companies lose interest. The art of making Really Good Tubes is gone.
As for ebay being risky, yes, it is. But it's less so today than when I first started using it in the 90s. You do need to keep your eyes open, and know a lot about what you're looking for. I've had a couple expensive deals in the last 8 months or so, but most of the people I've dealt with on ebay are good folks, who honestly describe what they sell. I've even run into a few Really Good Deals (like old Mullard's for under $10 or $20 bucks), but those are usually unbalanced/test low and are quite rare. However, there are lots of good old American tubes for sale cheaply (I bought a Raytheon long black plate 12AU7 not long ago for under $12 shipped). The best deal I found was a man selling 5963 tubes for $2.50 each (I bought a half dozen lol). Best thing to do is buy from someone with a 100% positive feedback. The people who are highly rated don't usually risk that rating on one bad deal.
. Second, I have not heard the Audiolab DAC hence I cannot be of any value add in terms of comparison. To my ears, the Bifrost/Lyr is a great combination and the Uber upgrades the Bifrost to (almost) the Gungnir.
