ECC83 Telefunken 12AX7 Types
My regular job does not have any connections with vacuum tubes, except for the music endlessly playing on my tube amplifiers. One day, in the middle of work time, a colleague entered my office to ask something and from the corner of my eye I glimpsed a man who was staring like hypnotized into an amplifier. While she was leaving, I called her out to leave the door ajar.
The modest man in mid-fifties was turning and gazing like a little kid around a new toy. I went out to get to know him and have a chat. Another tube freak and a new instant friendship. Word by word, and an invitation followed to visit him to review his system and listen to some tracks.
I visited him a few days later. The wine was poured and, with the music and the first impressions of the system, his story began about a dream system that he had pursued for decades and that was still missing a nuance to reach the sonic nirvana. As a final point, he proudly showed me a couple of freshly purchased vacuum tubes, recounting all he was through and the thorny paths that led him to a pair of original balanced Telefunken NOS ECC83.
The fresh, strong print on them and a quick look at the getter – in a split second, everything was clear as day to me. I did not mean to be rude, so I told him that it seemed to me that maybe they were not original. He smiled winningly and turned off the preamplifier, poured more wine, carefully took out the tubes, turned them and pointed to the diamond bottom with a smile from tooth to tooth.
Usually people are pretty cheer after the second bottle of an excellent wine. This time it was not the case. After my short explanation why they were not genuine, supported by irrefutable facts, my host looked sunken. A serious man with a serious business was seriously nervous. I felt a little sorry for him, so a few days later I invited him for a coffee near my company and gave him as a gift a pair of genuine DB (Diamond Bottom) – not NOS, but a low noise, balanced pair with lot of life. A SMS arrived few days later –“Finally nirvana!”
The fact is that all my life I have watched the world of tube music magic from a slightly different angle than most audiophiles. I have never been interested in sound just as sound, but in how the differences in the construction of vacuum tubes affect it. Examining all the details of internal construction of different tubes for the past 30-ish years, I acquired a routine to assess in a few seconds the type and the manufacturer in question. For most of other audiophiles, especially those with not-so-long path into tube rolling, that is a real enigma. The enigma turns into a nightmare as soon as they become proud owners of a “genuine” Telefunken ECC83 DB. Since several years ago, there is a cheap way to fake TFK embossed logo on the base of the tube using laser machines. (Of course, the faking does not end at the ECC83, there is a plenty of room for other preamplifier dual triodes and output tubes and I will try to write specific articles for most of them when I find free time.)
Telefunken is really the biggest brand among European tube manufacturers and, along with the Western Electric, the biggest one in the world. Their ECC83 is the most famous ECC83 / 12AX7 ever. Still today, the market for ECC83 is huge, with more than 2 million pieces sold yearly, mostly for guitar amplifiers, but also a good part for Hi Fi amplifiers and phono RIAAs made ever since the early 1950’s. Therefore, all the fame that accompanies DB ECC83 is understandable, and why they are so in demand even half a century after the end of production in Berlin and Ulm.
The variations in types and many tiny details, the early outsourcing of Telefunken, a great similarity with EI ECC83 tubes and the soaring demand for these real gems open a huge space for manipulation of resourceful resellers. The reputation of Telefunken ECC83 as a “dream tube” opened them an easy way to earn nicely on fake rebranded tubes in a relatively short period, selling through eBay and other digital platforms. All this, plus the painful experience of my new friend, prompted me to write this page about the types of Telefunken’s ECC83. If you want to buy something that has not been produced for half a century, something that has not even been talked about until 15-20 years ago, you have to make a little effort and learn something before bidding and buying.
The facts about ECC83 and a short type classification
All Tele’s ECC83 / 12AX7 are long (17 mm) plates vs. normal short (14 mm) plates.
Telefunken ECC83 long (17mm) smooth plates (on the left); EI ECC83K, well known among audiophiles as “short (14mm) smooth plate ECC83”, an extremely rare and surprisingly well sounding ECC83 / 12AX7 (right)
There are two main types: smooth plates and ribbed plates.
The smooth plates are more desired by audiophiles. They have been made in quite more versions than ribbed plates; hence, much greater attention is paid to them.
Smooth plate types
There are even five different types of smooth plates ECC83 12AX7 Telefunken:
- No holes (actually, there are two semi holes at the end of the plates, but this type is well known among audiophiles like „no holes“)
- Two holes (most produced type)
- Two holes – centered or two small holes
- Three holes
- Four holes
This type is very rare; it is also recognizable by the specific stop mica.
In more than 20 years of production of ECC83 in Berlin and Ulm tube manufacturing plants, this was the most common type.
Two holes centered
This was also a very common type produced until the end of production. Be careful, almost all properly faked ECC83 are of this kind!
Not so common.
This type has the same internal plate construction as the two centered holes type, with the additional semi holes at the end of the plates.
Smooth plate variations
Almost every of these types has been made in few variations, depending on how plate crimps were oriented and which of three different stop micas were used. There are also variations on the bottom and top micas. In addition, there are further variations with grid posts; they can be of same length (symmetric) or of different lengths (asymmetric). Almost all Telefunken’s ECC83 have nickel grid posts, but there are copper grid posts, too (very rare!). If you add the way the plate ears are bent (or not), type of bulb and where the getter is attached to the plate ear, the number of all possible variations surpasses one hundred.
- Inside – inside
- Inside – outside
- Outside – outside
Another variation is the top stop mica.
You can see that the no holes version and the two holes centered version have a different stop mica, which does not cover the full surface of the top mica. Bottom micas are also different.
The length of grid posts can be different, too. The two holes centered – asymmetric grid posts on the left vs. the symmetric grid posts on the right
The ribbed plates have always been made with the same types of plates. There are copper grid post and nickel grid post versions. Furthermore, the grid posts can be symmetric or asymmetric. The mica spacers can also cover the full surface or a part of the top mica.
Here is shown the difference in length on one side of grid posts.
Telefunken thick ring getter (The crucial fact for the end!)
Look carefully at this photo. If we ignore the etched tube codes, these two tubes seem identical. Actually, they are: both are with long smooth plates, two holes centered, and the mica spacers are identical. Just one tiny detail is different: the getter and the joint point where the getter arm is welded to the ring getter. All genuine Telefunken tubes have this type of getter.
It is better visible on the following photo of ECC83 with broken bulbs. The one with ribbed plates was used as it was at hand, but the same applies to those with smooth plates too. It is not a perfect circle, – it has a previously punctated point where the getter arm needs to be welded, and that is why it looks different from any other getter. This is the crucial detail to pay attention to if you want to be sure what you are buying.
A bit about codes. There are so many pages and articles about Telefunken date codes, but with all those facts, it still cannot be determined for sure in which period which type was produced and in which factory – Berlin or Ulm. In addition, it is not possible to know which type is in question only according to the code, as at Philips. Another confusing moment is that after 1963 a lot of Telefunken’s ECC83 have been made in EI factory in Niš, Serbia. Despite the fact that all of them have been coded and printed in Germany, there are many anomalies in codes and I cannot figure out which algorithm to use. During the last 30 years, I have collected more than 1400 codes of different types of Telefunken’s ECC83 from Berlin and Ulm plants, and it seems that I need more to get a perfect algorithm. If you are reading this and wish to contribute, please take a photo of your ECC83 with still visible codes and send it to my email.
Meanwhile, you can use this simple algorithm for most of Tele’s ECC83 production:
– B or U – Berlin or Ulm plant (mostly Berlin),
– First two digits in reverse order – day of month,
– Third and fourth digit – month,
– Fifth digit – year of production
– Sixth and seventh digits are always 01 – type code for ECC83,
– Sixth and seventh digits are always 01 – type code for ECC83.
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