Month=third and fifth digits=08=August Year=fourth digit is the year, 8=1968. Genuine Telefunken Germany (Berlin and Ulm) made tubes have a diamond mark molded into the glass between the pins.
The bottom line for buying tubes for your amp: we list types together that will work in your amp without problems. As mentioned in the answer to the previous question, some types (usually the popular ones) are referred to by different numbering systems.
There are many different tube substitution possibilities for those wishing to push the limits in the quest for unique performance, but our site is straightforward for those who just want to re-tube their amp without any extra concerns.
5751), or are some combination of numbers and letters (12AX7, ECC83, CV4004). If you aren't sure why some weird tube is in the clearly labelled socket of the amp you just bought, ask us or pick up a handbook and check for yourself. Also, much like vintage amplifiers and guitars (or vintage tuners and stereos), certain items achieve anointed status and their demand is even higher than usual, which also pushes the price higher. Most modern amps are designed around current production tubes for the good reason that they know you will be able to re-tube your amp in the future, and so these modern designs tend to sound best with current tubes. A simple guide is to replace the power tubes twice as often as the preamp tubes, because they wear out more quickly. If you're desperate, send us an email and we'll see if we can find it for you. Do you have brands like Siemens, Telefunken, or Mullard? Many of these types are impossible to find in large enough quantities to do tube matching, but we do get them occasionally.
These different numbering systems may be from the American or British military, or from American or European industrial or consumer use, and then of course there are many strange exceptions. There are thousands of tubes with identical basing, and the vast majority of them won't work in your amp. An amp that is used every day should expect to replace its power tubes every one or two years. If you see them available on our site, they usually won't be in stock for long!
Here is an example of a tube box and tube guarantee from Telefunken in 1938.
No doubt, radio tubes back then still cost upwards of a day's wages!
These are all European made tubes (except the Russian fake). Bugle Boy - 4 seams on top - note the 50s logo on the box.
In the last years of Amperex the tubes were mostly General Electric.
a A 1-46 a B 2-46 ab 4-31 ac 1-49 ad 7-44 ae 4-32 af 2-49 ag 5-32 ah 7-47 ai 5-31? ao 3-49 ap 1-45 aq 1-55 ar 1-39 as 2-55 at 3-55 au 6-31?