There is quite a lot being written about how "they just don't make them like they used to"; and when you think about it, all high end audio gear in the 1950's and most of the 60's was tube gear - so there was the cutting edge R & D technology and corporate global muscle driving the quality of the manufacturing. Not so today, although there is a niche market. It appears that as a result, the vintage tubes were made to withstand more hours of hard use than the new tubes. Aside from the tone differences, I'm not sure the durability factor alone of the vintage tubes will warrant the cost differential with the new tubes - except for maybe strong vintage RCA tubes picked up at a really good price in lots for $10 each.

So, if like me, you also want to try the "higher end" 12AX7 tubes from the 50's and 60's, you may may need to go on eBay to find them; as there is a global presence there. You also may get a much price on eBay than from Brent Jesse, the Tube Depot, or other top audio dealers. It can get a bit risky with vintage gear, as you really don't know how it was treated over 40 or 50 years; but if you stick to sellers with 98+ feedback that post tube tester measurements, you can get some very good deals. You may have to lose quite a few auctions to get a good tube at a low price; and it pays to "snipe" a bid at the end, if you arrange to be there when the auction ends.

Here's what to look for, IMO:

1) For all round balanced performance on the mid-rangy side and nice shimmer: Phillips (Amperex, Bugle Boy) tubes branded with three or four digit date codes, all beginning with a Delta symbol for the Heerlen, Holland plant. The three digit tubes are from the '50s; the four digit tubes are from the '60's - the number following the delta is the last digit of the year, and the third digit is the letter corresponding to the month (A=Jan, B=Feb, etc). Look particularly for the 17mm long plate tubes with foil D-getters and copper grid posts, or the triple-mica Phillips SQ tubes. Expect to pay $80 - $125 for the Bugle Boy D-getter tubes, and $40 - $80 for the long plate Halo, or round getter tubes with copper grid posts. Short plate 14 mm halo getter Bugle Boy tubes go for $30 - $50. Skip the Orange Globes and really short plate versions.

2) For a warmer tone than the Dutch tubes, but also a lot of presence and mid-range: Mullard tubes branded with three or four digit date codes from the 50's and 60's (like the above) beginning either with a B for the Blackburn, England plant, or an R for the Mitcham plant. Brimar (British Marconi) tubes are also just as good, but have their own idisyncratic date codes. Look particularly for the box plate CV4004 or M8137 tubes, the long-plate square or D-getter tubes with copper grid posts, and the Brimar 6057 tubes. Expect to pay $80 - $125 for the square getter tubes, and $60 - $100 for the box plate tubes. Long plate halo getter tubes with copper grid posts go for $50 - $100, and the 14mm short plate tubes $40 - $80. Also the gold colored Mullard shield 14mm plate tubes appear to have a higher gain than the white shield Mullards at the same price; and the 10M tubes (10,000 hour life) tubes with 14mm plates go for $100 - $200 per tube, depending on the condition. Skip the newer IEC labeled tubes with really short plates.

3) For even and accurate tone and linear presentation: Telefunken, Siemens and Valvo tubes. The date and manufacturing codes are confusing with the Telefunken tubes - but look for Siemens and Valvo tubes that have date codes beginning with a D for the Hamburg plant, or the vertical ++ symbol for the Munich plant. Telefunken tubes should have a diamond or square shape <> embossed in the bottom glass. The tubes will always have a halo getter, but look for the 17mm long plate tubes. Valvo tubes may have a halo getter welded to the plates at a 45 degree angle, which is highly sought after. Expect to pay $40 - $80 for the most German tubes, and the sloped halo getter Valvo's go for $80 - $120. The Telefunken ECC803S with the dual-support halo getter, thick box plates and gold pins is possibly the longest lasting 12AX7, and the most expensive at $300 - $800, depending on the condition. If you can find the older Siemens D-getter tubes, snatch them up. Skip the East German RTF tubes.

4) I have only had experience with RCA and GE vintage tubes made in the USA, and all I can say is that the RCA long black plate tube with a square getter, and the RCA 7025's and the triple-mica 5751 are great tubes - I think better than the GE versions. I was not thrilled with the lower gain 5751 in my rigs though. A CBS 7729 with gold pins was also tried, but that sounded too sterile and flat for my taste, although it was a quiet tube. Expect to pay $20 - $40 for the RCA long black plates, and $15 - $30 for the 5751's and the 7025's.

Some note on the condition of tubes:

1) Collectors in Asia pay a premium price for tubes with clear and pretty silk-screened logos. These easily wear off. That means you can get high-performance tubes with faint or even no logos at really bargain prices. Expect to pay on the lower end of the ranges above for a no-logo tube.

2) Look for high mutual conductance test readings if possible. The seller should provide readings for each of the two tube triodes, and the closer they are together, the better the tube will perform. Also the higher the values, the better the condition is and life expectancy of the tube will be. Make sure the seller divulges what the reference values are with his tester, for either a good or a new tube. Be suspicious of a used tube from the '50's tests "better than NOS" (new Old Stock). That seller is most likely either not using the tester correctly, using a poorly calibrated tester, or is outright lying. Now, I have a Hickok 800 that I can set up so that a reading of 1250 micromhos is an average new tube; but I can also set the tester up so that 1250 is a minimum good reading. A tube that measures over 1000 on each triode, when set up for 1250 = new, is a pretty strong tube. That same tube will read 1900 or better, when the tester is set up for 1250 = minimum good. Tube output in mA is not as good a measurement as ones in micromhos, because the tube can have a high output now, but a short life span ahead.

3) There are some tubes on the market that were specially selected by the manufacturers for being low-noise and sensitive for critical medical and scientific applications. The German scientific and medical selected tubes typically have a red enameled tip. The Phillips Bugle Boys with the treble clef logo next to the tube cartoon were also singled out at the factory for musical applications. The Brimar "T" tubes had a special coating inside to reduce microphonics and the like.

Well now you have my tube dissertation. I hope I wasn't too boring. Happy tube hunting, and I would like to hear your comments and / or questions!