原帖由 llhu 于 2008-12-8 14:21:00 发表
决心搞两对TFK的CCa,看看能带来啥变化. |
不如来两对早期的Siemens CCa来的划算:
看下面的文章:
Best of 6DJ8 (( 摘錄 ))
There are 14 candidates chosen for the evaluation and they are divided into three groups :
Group 1 (5 types) - All Telefunken
Group 2 (5 types) - All UK made
Group 3 (4 types) - German/US made
Although I have 5 more types of 6DJ8 from Holland include the famous "Bugle Boy", none, in my opinion, can match the performance of the tubes above apart from maybe the square getter "Bugle Boy". But as I only have one such tube, it cannot make the match this time. Another noticeable omission is the Mullard "pinched bottle" 6922 made by Amperex/Philips Holland, which has been described as "Best of the best" by Audiophile. I have been looking for this tube around the world (through the net) for the last 6 months and still without any success. Would welcome if anyone can tell me where to find a pair of these.
The game rule we used is, firstly, to identify the best tube out of each of the three groups. The 3 winner will then be compared against each other to find out which one is the "Best of the best".
Blind testing is performed and all judges have no idea what tube is in which group and what is the order of each. Code name is used for each tube and the model/type is only disclosed after the completion of each group test.
A score sheet is used but it is more as a decision aid. Score is to be given for each tube on 5 categories :
- Treble
- Mid-range
- Bass
- Transience
- Resolution
At the request of the judges, we added another column for "Musicality". A total score is required from each tube but the judges are reminded that the sum of the score does not need to be equal to the sum of scores in the 6 categories. The goal is to identify the best tube in each group and the overall winner.
2 x each type of tubes are used. Most are matched pairs but this is actually not too critical in the testing setup which is as follows :
CD : Sony S7000 + Theta TLC + Adcom GDA 600 + WE93F
Pre-amp : ARC LS-7
Power Amp : 2 x Audion Sterling (in monoblock single EL34 mode)
Speaker : KEF LS3/5a (Piano)
Each pair of tube is used on the input buffer of the Audion Sterling. This is, in my opinion, the most sensitive to tube change compare to used in the pre-amp or as driver.
The Audion Sterling is with Valve Art EL34 and Raytheon square getter 5687 for the group test. Telefunken metal base EL34 were used for final.
There is significant shortcoming of this setup, namely, the lack of bass impact. But I think we still were able to distinguish the bass performance from one tube to the other.
Software used for the test are :
1. Jekyll and Hyde - 1st track
2. David Oistraich - 2nd track
3. Passion of Classics (HDCD version) - 2nd track
4. Cafe Blue - 3rd track
Group 1 - Telefunken
There are 5 types of tube in this group and they are all made by the famous Telefunken with <> marking at bottom :
1. ECC88
2. E88CC (gold pin)
3. E188CC (gold pin)
4. CCa (gold pin)
5. CCa (old type)
Some of you might know that there is also a E288CC from Telefunken. But this is, in fact, not made by Telefunken but Siemens. And it is represented in Group 3.
We are all surprised by the difference in performance with the tubes made by the same firm - Telefunken.
But the result is, in a way, not surprising at all. The most expensive ($1,500 each) of all these tubes, the E188CC won. The runner-up is the old type CCa. The winning margin from the rest of the group is VERY significant. According to some of the judges, it is like changing to a completely different set of hifi with this tube. We very nearly declare this to be the "best of the best" without testing the others.
Group 2 – Tubes from UK
The tubes in Group 2 are all made in UK. They are :
Mullard E88CC (wrinkle glass, "British Made")
Ediswan 6DJ8/CV5358 (a special low-noise 6DJ8 made by Mullard)
Brimar E88CC
GEC CV2492 (blue label)
GEC E88CC (light green label)
This proves to be a "bloody" match as they are much closer in performance. The greatest disappointment is with the wrinkle glass Mullard. This is an expensive tube (about $1,000) and was judged to be the "best of the best 6DJ8" by Audiophile before. But in terms of performance, it comes at the bottom of this group.
Some of you might ask why the Brimar E88CC is included as this tube is not particularly well known and costs only $250. Well, the reason is because this tube is completely identical to the GEC CV2492, which is selling for $1,500 in Hong Kong at present! I am sure no one can tell the difference between the internal and external structure of these two tubes even when looking through a microscope. I am sure the GEC CV2492 was, in fact, made by Brimar. But the result is quite a revelation to me…
The GEC CV2492 came out as the winner of this group where the Brimar was rated as the second worst in the group. This proves that selection is a far more important factor than the construction of the tube itself. And the tube market is actually rather efficient in term of pricing.
Having said that, the GEC 2492 actually beat the GEC E88CC (light green label), which is actually more expensive (around $2,000 each), even though it is only by a very very narrow margin.
Although the GEC 6DJ8 has proved to be one of the best such tube in the world, I would like to warn any person who is looking to buy this tube as there are more than 6 types of GEC 6DJ8/6922 that I have seen and that are all different. The price of them is from $200 to $2000 each. The reason is because GEC has never made a 6DJ8/6922 and was buying from Mullard, Brimar and other tube makers over the years. So they are all different and the performance varies a great deal. If you really want to look for this GEC CV2492 that won the UK group test, you would probably need to buy a Brimar E88CC first and look for a GEC CV2492 with internal structure that look exactly the same.
Group 3 – Germany/USA
3 of the tubes from Group 3 are made by Siemens and the last one is from USA :
Siemens E288CC/8223 (old type)
Siemens E188CC/7308
Siemens CCa (old type)
Amperex 7308 "PQ"
I think some of you might know that the E288CC/8223 is the highest spec in the 6DJ8 family. But it proves to be the worst sounding tube in this group. Bear in mind that this is already the old version of the E288CC which cost over $600 each.
The Amperex gave a very good performance and proved to be a best-buy given its price is only around $400. But it still came second after the Siemens CCa, which came out as a clear winner of this group.
BEST OF THE BEST
After over 4 hours of testing, we finally came to the Grand Final – of finding out which one is indeed, the BEST OF THE BEST 6DJ8 in the world.
In order to erase previous memory of which tube is which by the sound, I have change the output tube to the Telefunken metal base EL34, one of the best EL34 ever made, and put the Telefunken E188CC, GEC CV2492 and Siemens CCa to the final test.
Same test is used but we change one of the test track, Passion of Classics-2nd track, to the piano music of Chopin – Naum Starkman – 2nd track..
The final proved to be extremely close and we actually have to retest the first tube again to try to determine the result (by eliminating the disadvantage of testing it when the Telefunken EL34 was at its lowest temperature).
The result was actually so close that the overall winner won by, literally, decimal point over the other two. And we also found out each of the 3 finalist has at least one strength that is better than the other two, and they are :
Telefunken E188CC - Best Transience
GEC CV2492 - Best Dynamics
Siemens CCa - Best Resolution
At the end of the day, we concluded that the Siemens CCa is the overall winner and won the title of "BEST OF THE BEST 6DJ8 IN THE WORLD". It has the highest resolution power of all of the 14 tubes and also the best total score when everything is counted.
But before you rush out to the nearest tube shop and buy every Siemens CCa in sight. Another word of warning :
The overall winner is the "early type" of Siemens CCa. The later production types are much worse and nowhere near any of the 14 tubes tested here. The early type of CCa has a slightly different structure compare to the later types. If you look at the plates between the two plate insulators, make sure every plate is grey with NO shiny metal plate on the two sides support the upper structure. The box should be in yellow/blue color instead of white/orange/blue or orange/blue. The price varies by a huge amount. I bought a pair with no box for $300 each but another NIB I saw in another shop is selling for $1,600 each.
