Core, I have bought all my tubes from either ebay or Decware members. On ebay it's important to look at feedback...if people are not satisfied they are likely to leave negative feedback, more so than positive when happy with the transaction. I sometimes read the negatives if it's a new seller to me. Also, I usually, but not always require test results, the name of the tester and the minimum good value and NOS value for the tester used. Photos are key...so you can look for yourself for characteristics that should be seen. Also, sometimes the tube described is not really what you see...ie... a date is given that isn't confirmed by date codes on the tube or when labeling is worn the seller may have erroneously listed the wrong brand. Also ask if you have questions...sometimes the best deals are where the seller has done a poor job describing and listing the tube. If a seller is unwilling to reply to your question...take a pass.
For a long time I didn't buy from foreign sellers but have relaxed this a bit. I've bought Russian tubes from Russian/Eastern European sellers that have high feedback scores and other Decware members have bought from without incident. Normally shipping is so much higher it's not worth buying anywhere except the USA...provided that's where you live.
There are numerous blogs and sites where helpful info can be obtained...two that helped me were Joe's Tube Lore and Brent Jesse's site but there are many more sites...just do google searches. The Decware site has lots of impressions on tubes used in Decware Gear and lots of helpful Audio Nuts that have already gone through the journey you're starting. Again do searches.
I have copied some info on counterfeits from both sites and given you the links below. There are often deals on nice strong tubes if you are patient. For example, the pair of good testing 1965 Amperex Bugle Boys I bought last summer cost $30...a great deal. But you can always buy from a reputable dealer for a lot more and not have to go through the hassles of learning about what you're buying. I actually enjoy the search and especially finding a gem that others have overlooked. Good Luck, if you have other questions, I'll try to answer. Mark.
http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html#6DJ8Danger Will Robinson!
Be careful when you chase these guys. The reputation of Siemens & Amperexes precedes them and they are frequent targets for counterfeiters. How do you know if a tube in question is the genuine article? Well, fortunately there are a few basic checks you can perform to differentiate true Siemens & Amperexes from relabeled Sylvanias and Tungsrams.
First, check the top of the tube in question. Siemens & Amperexes always have small ridges in the surface of the glass on top of the tube radiating outward from the nipple. These tubes will have 4 ridges, though sometimes only two of them are easily visible. The concept here is to look down on the top of the tube. The 2 or 4 ridges should divide the circular silver top of the tube in half or into quarters. No ridges? No genuine article pass on it.
Second, check the metal shield above the upper mica spacer. On Siemens & Amperexes it’s circular with two raised rectangular sections on opposite edges of the shield. On most fakes that shield is a perfectly flat disc.
Third, about 90% of Siemens tubes have a 1 or 2 digit number molded into the inside bottom of the tube glass centered between the pins. It can sometimes be very hard to see but it’s usually there. Remember, not all Siemens have it, but if your tube passes test one & two and has the number(s), it's a Siemens.
Fourth, familiarize yourself with the shape of the glass bottle on your stock Sovteks. Note that the top is smooth (no ridges) and rather rounded and the tube is short & large in diameter these traits are common to all Russian tubes in this family. Siemens & Amperexes are only about 80 to 85% of the diameter of the Russian versions and tend to have squarer shoulders on top rather than the rounded top of the Sovtek. You should be able to spot the difference between a Russian and a genuine NOS tube just by the shape & diameter of the glass pretty easily. One warning though Sovteks often (always?) have a number molded into the bottom of the tube between the pins like a Siemens, so know all the checks and don’t depend on just one to verify the tubes origins.
Fifth, if it’s a Siemens or Amperex 6922 or 7308 it will always have gold pins. So will some cheap counterfeits, so gold is no guarantee. But if they aren’t gold its not a Siemens or Amperex, so pass on it.
http://www.audiotubes.com/6dj8.htmA Note About Amperex 6922 and Bugle Boy Tubes:
Because the trade names of "Amperex" and "Bugle Boy" have been sold to a USA electronics firm, there is much confusion in the tube world about Bugle Boy tubes. I will try to clear up the confusion as briefly as possible. This company bought the rights to the name Amperex, the name Bugle Boy, and the rights to the cartoon tube logo. This new owner is NOT Dutch Philips or North American Philips, who originally owned Amperex and made the 1950s to 1970s vintage tubes that audiophiles want. When I mention "Amperex Holland" or "Amperex USA", I refer to the original Dutch and North Amperican Philips owned companies (now defunct) that made the vintage tubes, now in demand by audiophiles, up until the late 1970s. There are 6922 tubes being sold today under the name Amperex Bugle Boy, and they even come in a green and yellow box like the original Amperex tubes. THESE ARE NOT AMPEREX TUBES AT ALL, AND THEY ARE NOT NOS. They are either relabeled new Chinese or late production JAN Sylvania tubes. These fakes contain several errors:
1. Genuine NOS Amperex Holland or Amperex USA NEVER used the words "Bugle Boy" on their tubes or boxes.
2. Genuine NOS Amperex tubes NEVER had the cartoon Bugle Boy printed on the tube box.
3. Philips/Amperex Holland or North American Philips/Amperex USA NEVER made a 6922 (E88CC) tube with the Bugle Boy cartoon on the box. They also NEVER made a 7308 or E188CC with the Bugle Boy on the box OR glass. In this family of tubes, only the 6DJ8 had the cartoon tube on the glass, but again, never on the box.
4. Again, there IS NO SUCH THING as a genuine NOS Amperex "Bugle Boy" 6922 or 7308 tube. This bears repeating!
5. We stock the real NOS 1960s and 1970s Amperex (Holland and USA made) 6922 and 7308 tubes. They either used the white label or the orange (or later green) globe logo label, with either the PQ (premium quality) logo, or were military USN/CEP or JAN labeled. We also stock the real NOS Holland 6DJ8 Bugle Boy tubes from the 1960s. Amperex did not make these in the USA. These DO have the cartoon boy on the label, but NEVER had the words "Bugle Boy" printed on the box or the tube glass.
6. Nearly all of the NOS 1960s and 1970s real Amperex tubes have the factory date codes on the side of the glass. The fakes do not.
7. Some knowledgeable sources have reported seeing recently some Amperex HOLLAND made 6922 gold pin tubes with the Bugle Boy cartoon on the glass. They were only Holland made and only 6922 type. It appears there were so few made in the early 1960s that it is unlikely any will turn up anywhere outside of The Netherlands or neighboring countries in Europe. Determining if they are real by the date code and other construction factors requires some skill. Since they are so scarce, it is advisable to treat any "Bugle Boy" 6922 tube as a fake.