mab1376
1000+ Head-Fier
Fellow 6n6p-ir owners, whats you date codes? Mine is 89@11
i'm going to buy a new set from 1983 or earlier.
i'm going to buy a new set from 1983 or earlier.
Little Dot Tube Amps: Vacuum Tube Rolling Guide
- Thread starter Dept_of_Alchemy
- Start date
siles1991
100+ Head-Fier
- Joined
- Apr 12, 2013
- Posts
- 213
- Likes
- 12
mine shows 02*pentagon*83 so I assume it's 1983 but not sure how to read the 02.
mab1376
1000+ Head-Fier
Should mean second week of the year.
I just ordered a pair with 12*pentagon*74, anything from 1983 and earlier supposedly was made in a factory with special materials that were renowned for quality.
One of these days i'll get the 6H30P-DR
mordy
Headphoneus Supremus
- Joined
- Aug 8, 2010
- Posts
- 7,709
- Likes
- 7,406
It is my impression that Russian tubes are date marked with the month/year. 02-74 would be February 1976. I have seen Russian tubes using Roman numerals for the month. April 1976 would be IV/76.
US tubes usually use year/week or some encryption. (Just got a pair of RCA 6CS6 tubes with date code MM. For this you need a chart. In this case it is Nov 1961.)
Strangely enough, I have not been able to find charts that decipher the encrypted date codes on Tung Sol and Sylvania tubes. One reason to keep the manufacturing dates secret was to ensure that people would not worry about buying older tubes since they could not figure out when they were made.
In retrospect this is also strange - we would rather buy older, 60 year old tubes than newer ones from the eighties since we now know that the earlier ones many times were better made.
US tubes usually use year/week or some encryption. (Just got a pair of RCA 6CS6 tubes with date code MM. For this you need a chart. In this case it is Nov 1961.)
Strangely enough, I have not been able to find charts that decipher the encrypted date codes on Tung Sol and Sylvania tubes. One reason to keep the manufacturing dates secret was to ensure that people would not worry about buying older tubes since they could not figure out when they were made.
In retrospect this is also strange - we would rather buy older, 60 year old tubes than newer ones from the eighties since we now know that the earlier ones many times were better made.
Quote:
Sylvania and Tung-Sol date codes must be some of the best kept secrets on this planet.
Sylvania and Tung-Sol date codes must be some of the best kept secrets on this planet.
mab1376
1000+ Head-Fier
Quote:
I'm curious to see how my new ones from 1974 compare to my current ones from 1989.
I'm curious to see how my new ones from 1974 compare to my current ones from 1989.
gibosi
Headphoneus Supremus
- Joined
- Oct 18, 2012
- Posts
- 6,431
- Likes
- 4,834
Quote:
After about 28 hours, these Tung Sol 6TD6 are some seriously good tubes. Going by memory, they remind me of the Tung-Sol 6485, with great bass, effortless treble detail and clear vocals that seem to be etched in space. I need to spend some time directly comparing them with the 6485, and further, since these can be strapped 1-7, I feel strongly that I should try them in that configuration too.... Thinking about how that might sound is very intriguing.....
After about 28 hours, these Tung Sol 6TD6 are some seriously good tubes. Going by memory, they remind me of the Tung-Sol 6485, with great bass, effortless treble detail and clear vocals that seem to be etched in space. I need to spend some time directly comparing them with the 6485, and further, since these can be strapped 1-7, I feel strongly that I should try them in that configuration too.... Thinking about how that might sound is very intriguing.....
Quote:
Quote:
We discussed this in PM and Mordy thought that I should repeat some of that in this thread, so here it is. This is the tube in question:
I don't think "noval" is a brand here, so EK must be the brand.
The branding is exactly like Ei's. Ei at some point had noval-sized and magnoval-sized boxes with those words printed on them:
Apparently "magnoval" boxes didn't always contain magnoval-based tubes:
Why not 7-pin tubes in "noval" boxes then?
Ei (Elektronska industrija) made tubes in Niš, Yugoslavia. These were also sold under other brands, including Siemens:
In conclusion, the EK-branded tube was – possibly – made by Ei – or maybe not.
Quote:
We discussed this in PM and Mordy thought that I should repeat some of that in this thread, so here it is. This is the tube in question:
I don't think "noval" is a brand here, so EK must be the brand.
The branding is exactly like Ei's. Ei at some point had noval-sized and magnoval-sized boxes with those words printed on them:
- http://www.ebay.com.sg/itm/NOS-1-MATCHED-pair-exact-EI-PCC88-7DJ8-TUBES-similar-ECC88-6DJ8-Amplitrex-/251094753127
- http://www.tubes.rs/Tubes/NOS/Audio/OutPentodes/EL509_EL519_6KG6/PL519_40KG6_EI_Yugoslavia.html
Apparently "magnoval" boxes didn't always contain magnoval-based tubes:
- http://www.elektroncso.hu/kepek/kt90_ei.jpg
- http://www.jogis-roehrenbude.de/EL34-Story/EL34-Story-Seite5.htm
Why not 7-pin tubes in "noval" boxes then?
Ei (Elektronska industrija) made tubes in Niš, Yugoslavia. These were also sold under other brands, including Siemens:
In conclusion, the EK-branded tube was – possibly – made by Ei – or maybe not.
gibosi
Headphoneus Supremus
- Joined
- Oct 18, 2012
- Posts
- 6,431
- Likes
- 4,834
Quote:
Since I think I am the only one who has the 6HZ6 and 6DT6, I wanted to let people know that I have briefly tried the Tung-Sol in all four configurations: unstrapped EF95, unstrapped EF91/92, strapped 1-7 and strapped 2-7. I listened to just one song in each setting as my goal was to verify that each of these settings is valid. And indeed, there is no distortion or anything unusual, and therefore, it will require some time to understand the differences, and then, to decide which is best.
I have decided to start with the strapped 2-7 configuration as the RCA data sheet for the 6DT6 actually suggests two strapping options: (1) connecting grid 1 to the cathode and (2) connecting grid 3 to cathode. While connecting grid 1 to the cathode would require a specially built socket adapter, we can easily connect grid 3 to the cathode as has been routine with 6AU6 and 6AH6. Will report back when I know more.
I sure hope someone else will be getting some of these tubes shortly. It would be great to get a another opinion, or two.
Since I think I am the only one who has the 6HZ6 and 6DT6, I wanted to let people know that I have briefly tried the Tung-Sol in all four configurations: unstrapped EF95, unstrapped EF91/92, strapped 1-7 and strapped 2-7. I listened to just one song in each setting as my goal was to verify that each of these settings is valid. And indeed, there is no distortion or anything unusual, and therefore, it will require some time to understand the differences, and then, to decide which is best.
I have decided to start with the strapped 2-7 configuration as the RCA data sheet for the 6DT6 actually suggests two strapping options: (1) connecting grid 1 to the cathode and (2) connecting grid 3 to cathode. While connecting grid 1 to the cathode would require a specially built socket adapter, we can easily connect grid 3 to the cathode as has been routine with 6AU6 and 6AH6. Will report back when I know more.
I sure hope someone else will be getting some of these tubes shortly. It would be great to get a another opinion, or two.
kvtaco17
Headphoneus Supremus
- Joined
- Mar 29, 2013
- Posts
- 1,718
- Likes
- 247
- Joined
- Apr 12, 2012
- Posts
- 671
- Likes
- 75
Heptodes!
After a while of living with a few German, Dutch, English and Russian heptodes, here are my impressions.
I have ranked them in order to give the review a better structure. A priori, the level of these tubes is rather high, so you could easily live with the lowest of these tubes happily until the end of its tube life. However, you are likely to get more detail out of one of the better tubes. Ranking from 1 being the best to 4 being the worst within this review. Rank 2 is subdivided from (a) being the best down to (d).
The main differences affect tonality/signature and focus. If the signature as described suits you, you may prefer one lower ranked tube over a higher one. These are my impressions, all is IMHO and I understand that I am not agreeing in every point with former posts but there you go.
I have strapped the tubes as well, but used the unstrapped EF95 mode as the basic mode of operation.
Gear used: Foobar with WASAPI plugin, Audiolab M-DAC (Optimized Spectrum filter), UPOCC RCA cable, LD MKIII run via the regular input mode, Sennheiser HD800
Tubes tested in alphabetical order: Amperex E91H (6687), Brimar CV4012 (KB/AD), Lorenz SEL EK90, Siemens EH90 (foreign), Siemens EK90 (saucer getter), Telefunken EH90 (Ulm, Made in Germany), Telefunken EH900S (Ulm, Made in Germany, gold pins).
Starting from the bottom:
Rank 4
Svetlana 6A2P (6A2П) - 6BE6
October 1967
Firstly, you notice the refined character of the tube and the slightly warm signature. The tube has a refined treble, a bit too laid back for me. The mids are well presented. The strongest side of the tube is the bass. It is well articulated and presented with good weight. You cannot get tired listening to the 6A2P. Listening is quite engaging with good PRaT. However, the tube is not the most transparent one, which also leads to not the best focus. It lacks ambient impression and the stage is not very deep. Overall, an enjoyable tube especially if you are more on the bass head side.
1/7- and 2/7-strapping give similar results. The tube sounds more defined, brighter (“touch of triode”), not as bright as the Lorenz SEL EK90 and the treble is not as clean.
Rank 3
Siemens EH90 No logo, backside says EH90 in dark brown and “foreign” – 6CS6
678 indicates June 1978 (?)
Now, this is a difficult one. It sounds so good! Open, very good detail and focus, even toe tapping. The bass is punchy as well but lacks a bit in weight. The mids are a bit too hard for my liking. The signature is more on the cooler side and the tube is inclined towards the treble. Voices are well defined but a bit thin. I can imagine this tube to shine in the right system because it is of very good quality, which is also seen in the excellent instrument separation. Listening to it over a greater length of time makes me feel that I am missing some bass and warmth. Also, it becomes earlier fatiguing than any of the other tubes.
Rank 2 (d)
Amperex E91H (6687, Made in Holland) – 6BY6
Manufacturing code 42G5 – my interpretation: Venolanda SA in Venezuela, 5th week of July 1962
This would be the opposite of fatiguing: very refined sound, round treble. The Amperex delivers lots of detail, good instrument separation and resolution, all on a very wide and deep stage. The sound really is “out of your face”. J For me it sounds a bit too polite though, hence it loses the right kick. Although the bass goes deep and is of good weight, it lacks some punch. Mostly the treble is too laid back here.
Strapping! OK, this tubes gains with strapping 1/7 sounds more forward and makes it more engaging. More treble! More punch! 1/7 is a wetter version of the 2/7 strap. 2/7 strap makes it sound most forward with most definition. There is great gain in treble and bass punch. It loses some warmth, “organic and natural” part of the sound, which is better preserved in the 1/7-setting. With 1/7-strapping or 2/7, dependent on liking, it sounds better than the unstrapped Telefunken EH900S.
Recommended strapping: 1/7 > 2/7 > NS
Rank 2 (c)
Telefunken EH900S (Made in Germany, Gold pins) – 6BY6
Ulm, tube 1 from 24/10/1976 (U4206104), tube 2 from 09/11/1974 (U9014104F), tubes are supposedly matched.
Focus! Very good instrument separation. This is another one of the quite refined sounding tubes. This tube has a good tonality and with a slight warmth. It is more engaging than the unstrapped Amperex E91H and comes close to the 1/7-strapped Amperex. The bass weight is quite impressive and it goes deeeep (bass monster), which is lesser pronounced after the tube is fully burnt in. In comparison to the Siemens EK90, the bass is not as “clean” and overall it does not have the same dynamic presentation. For me, the TF EH900S does not sound too forward. I quite enjoy listening for longer spaces of time.
1/7-strapping defines the bass better, it becomes punchier. The tube sounds opener and brighter, a bit more forward as well but not fatigung. The balance is still good. This sounds better than unstrapped to me, in line with the Amperex impressions. Both are 6BY6 tubes of special quality. 2/7-strapping works even better. More punch, definition and some more “treble energy” making it sound more open, still with good ambient impression, not as forward as with the Amperex E91H. Quite engaging.
Recommended strapping: 2/7 > 1/7 > NS
Rank 2 (b)
Telefunken EH90 (Made in Germany) – 6CS6
Both tubes U6206922, which I interpret as Ulm, produced on the 26th of September 1979 (or 69?)
Very good separation, focus and transparency. Punchy and impactful bass, engaging, toe tapping, you know the words. It does sound great. Interestingly, the tube combines a few features not commonly coming together with heptodes: Treble is great - extended, but not overly refined as with the EH900S, yet the tube is quite dry for a heptode and relatively forward. More forward than the EH900S. The tonal balance is good. The signature is rather neutral. Fortunately, listening does not get fatiguing easily. I would have wished a bit more spatial information, hence the stage is presented rather flat. In summary, this tube is perfectly enjoyable as long as you don’t request an experience of ambience, which I am missing a bit.
2/7-strapping yields an intersting effect: The tube sounds wetter compensating out some of the flat stage. A bit of the focus gets lost though. With 1/7, the effect is weaker.
Depending on preference, I suggest non-strapped or 2/7. I just use non-strapped, which makes this tube sounding special in its own way.
Rank 2 (b)
Lorenz SEL EK90 – 6BE6
Labelled with 082 and BWB940 with eagle indicating that it was produced for the German Army
Now, this is quite a tube. Very good tonal balance. Sounds “fatter” than the Telefunken EH900S (and Amperex). After powering and listening, you immediately start to tap your toes. It has good dynamics, non-strapped good treble, refined but not rolled off. The bass hits hard with a good weight as well. The signature is slightly warm and very pleasing. The stage is well extended in width and sufficiently in depth with a very good ambient perception. You kind of have to like this tube. Its weakness is on the resolution side. It does not deliver the last word in terms of definition and instrument separation. Here, the Telefunken 2/7-strapped offers more. If your gear does resolve well, then you can extract more detail with better tubes. In summary, it is an engaging all round tube most people would appreciate.
Rank 2 (a)
Brimar CV4012 KB/AD (5750, 6BE6W) (= Haltron CV4012 (?)) - 6BE6
Haltron code: 1AB/3975
These tubes sound basically identical to my ears and look identical from the outside but one tiny bridge under the halo getter.
Now, I might out myself with this ranking but to me these are like the Lorenz with a slightly more refined treble and better resolution / definition. Their imaging is really good, instrument separation goes along very well and they are toe tapping. For me it is like: “yes, please more of this”. Very good PRaT. The bass, very good weight and presence. It is not the most punchy bass every heard, which may be the weaker side of the tube but is not overpowering in my setup. It still is rather well defined. Possibly, this is a good match for the HD800 though, which is not a bass monster but very punchy. I really like the treble as well. It is refined as for most of the tubes, extended, non-fatiguing and with a sufficiently good presence.
I can imagine that on a treble weaker system, this treble could become underrepresented. It works for me though. The stage and instrument separation are not as impressive as with the Siemens EK90.
Non-strapped: In my ears this sounds clean with the blackest background and natural at the same time. My favourite.
1/7-strapping improves bass puch and treble presence, whilst keeping ambience. It somewhat sounds wetter but it unfortunately also blurs the imaging slightly. If you cannot resolve the difference, then 1/7-strapping may be an option.
2/7 sounds brighter than NS with better instrument separation, imaging is similar but signature is drier
Recommended strapping: NS > 2/7 > 1/7
Rank 1
Aug 10, 2013 at 6:39 PM
Post #2,293 of 13,432
Aug 10, 2013 at 10:33 PM
Post #2,294 of 13,432
Aug 10, 2013 at 10:46 PM
Post #2,295 of 13,432
Siemens EK90 (no logo, saucer getter, black bottom) - 6BE6
933 with eagle on the side indicates that it was produced for the German Army. 278 on the side indicates Feb 1978 (?)
Here comes my favourite tube. Definition, ambience, wetness and a large stage. The stage is really nice, wide and deep. Black background. Wow. The tube sounds neutral with a warm hint. The bass is punchy and well articulated and goes deep. The treble is refined but not as much as for the special quality 6BY6 tubes. This makes the Siemens sound more dynamic and interesting. The mids are not forward but slightly laid back. The balance throughout the spectrum is good. This tube combines the best of almost all aspects. It is engaging and toe-tapping with great imaging. It sounds also analytical, so you will get all the details from your recording. Unstrapped is here clearly my preferred setting.
Shame this tube is not more easily available.
MIKELAP
Headphoneus Supremus
Thanks Acapella11 these reviews will be great adding them to page 77
mordy
Headphoneus Supremus
- Joined
- Aug 8, 2010
- Posts
- 7,709
- Likes
- 7,406
Hi Acapella11,
Congratulations on your extensive review! Very nice work. I must say that I admire your ability to express all the different nuances in how the tubes sound.
From wearing myself in reviewing heptodes I recognize the tremendous brain exercise involved to keep track of all the impressions from the various settings and then remember how the tubes sound, and after wards ranking them.
There is a publication in the US (I am sure there i a British counterpart) called Consumer Reports. They review a lot of stuff, including cars. My personal conclusion is that in rating cars there is a single rating that sort of is all inclusive. They ask owners if they would buy the same car again, and the percentages of people who would buy the same car again correlate well with the highest ranked cars in terms of functionality and reliability (with a few exceptions).
Now, my tongue in cheek proposal is to rate the tubes with a toe tapping index. On a scale of 1 to 5, (5 being the highest) how would you rate the tube?
I'll bet the best tubes are a 5....
Happy tube rolling!
Congratulations on your extensive review! Very nice work. I must say that I admire your ability to express all the different nuances in how the tubes sound.
From wearing myself in reviewing heptodes I recognize the tremendous brain exercise involved to keep track of all the impressions from the various settings and then remember how the tubes sound, and after wards ranking them.
There is a publication in the US (I am sure there i a British counterpart) called Consumer Reports. They review a lot of stuff, including cars. My personal conclusion is that in rating cars there is a single rating that sort of is all inclusive. They ask owners if they would buy the same car again, and the percentages of people who would buy the same car again correlate well with the highest ranked cars in terms of functionality and reliability (with a few exceptions).
Now, my tongue in cheek proposal is to rate the tubes with a toe tapping index. On a scale of 1 to 5, (5 being the highest) how would you rate the tube?
I'll bet the best tubes are a 5....
Happy tube rolling!
gibosi
Headphoneus Supremus
- Joined
- Oct 18, 2012
- Posts
- 6,431
- Likes
- 4,834
Quote:
Heptodes!
Tubes tested in alphabetical order: Amperex E91H (6687), Brimar CV4012 (KB/AD), Lorenz SEL EK90, Siemens EH90 (foreign), Siemens EK90 (saucer getter), Telefunken EH90 (Ulm, Made in Germany), Telefunken EH900S (Ulm, Made in Germany, gold pins).
Great job! I can appreciate how much time and energy it takes to audition 7 different heptodes (strapped and unstrapped), wrap your mind around each of them, and then present your results in a clear and easy to read fashion. And I have never tried to rank them, which makes such a project at least another order of magnitude more difficult!
The biggest surprise for me is the Brimar CV4012. I remember being less than impressed, but that was a couple of months ago, so I think I need to get them out for another listen. And regarding the "foreign" Siemens EH90, can I assume you tried 1-7 and 2-7 and came to the conclusion that unstrapped was the best setting?
Quote:Rank 1
Siemens EK90 (no logo, saucer getter, black bottom) - 6BE6
933 with eagle on the side indicates that it was produced for the German Army. 278 on the side indicates Feb 1978 (?)
Shame this tube is not more easily available.
It is obvious to me that only one pair of these tubes exist today, and with a huge bit of luck, you are the guy who has them. I would like to suggest that you consider sending them round robin to each of us so we can hear them too! lolUsers who are viewing this thread