[Johlke]

Do all Telefunken tubes have the diamond (i.e., "<>") on the bottom between the pins?  I've heard that the way to identify fake Telefunken tubes is to see if they have the diamond imprint on the bottom but it seems to me that any counterfeiter could easily reproduce it also.  I was digging around in my box of old tubes and found a couple of 12ax7s without the diamond and it got me wondering.

[JerryM]

Do all Telefunken tubes have the diamond (i.e., "<>") on the bottom between the pins?

Yes, all of them.

Counterfeiters don't make tubes; they silkscreen logos onto inexpensive tubes.

[jules]

Yes, I think all Telefunkens have the diamond. Fakes usually have slightly different looking internals so if you can compare a genuine item [or a good resolution photo] with a possible fake you might find the truth. I can't speak for the differences you might find in a 12ax7 though.

Do your tubes have the white printing on the outside of the tube and how does that look?

[LeeH]

My experience is that Telefunkens have the diamond on the base of the tube in between the pins

[Ericus Rex]

Lack of a diamond doesn't necessarily mean counterfeit.  Like with most NOS manufacturers, when they ran out of stock and couldn't fill a large order they would buy tubes from their competitors and rebrand them.  I think many of these non-diamond Teles are actually Mullards.  But, as mentioned before, all Tele made tubes have the diamond.  Post a pic of the innards and we'll have a better idea of what you have.

[Johlke]

Thanks to everyone for the helpful information.  Yes, it does appear that the non-diamond bottom Teles I have are re-branded tubes from another manufacturer and that all "real" Teles do indeed have the the diamond bottom.  FYI: an interesting hint I got from Steve Hoffman's website is to buy Dynaco or Fisher branded tubes as they are almost certainly authentic Telefunken 12ax7s.

Cheers and happy listening!

[Hank]

H.H. Scott also used Telefunken's.  There in my Scott LK-48B that I built when I was about 16.