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In Reply to: The 6DJ8 family posted by Bambi B on July 17, 2006 at 06:56:00:
"It's worthwhile to remember the 6DJ8 is usually thought to be the best sounding of the family."By Joe. Not necessarily by others. Please note that he emphasizes this point himself. One must be careful to help a newb keep an open mind. For an example of differing opinion, the 7308/E188CC has been king in pro audio circles for years, where it is used in some pretty famous preamps. I admit to being inclined the same way, and I have listened to most of what Joe has, save for the elusive CCa. Other folks like other tubes, and their opinion carries the same weight.
Tubes are like wine - you not only have to choose your favorite wines by trying them, you also have to pick a reviewer with the same taste as you. Joe's page is a wonderful survey, and a great labor of love. Use it to expand your horizons rather than to narrow them.
Follow Ups:
Doc B.,I'm not parroting Joe Rosen regarding the sonics of the 6DJ8 family. I use 17 in my 12 pieces of tube gear, have about 90 NOS of these types and have tried multiple versions of 6DJ8, 6922, and 7308.
I've tried:
6DJ8: [use: 4, 2, 8, 3]
Philips Miniwatt E188CC- Holland- NOS
Philips SQ E188CC- Holland -NOS- VR9
Valvo E188CC- Germany- NOS
Mullard E188CC- GB- NOS
Amperex CEP E188CC- US- NOS
Amperex Globe-ECC88 A frame-NOS
Siemens E188CC-Germany- Used
Siemens E88CC- NOS
RAM- ECC88 SA low noise Ampx A frame-NEW
RAM - A std- Ampx - A frm- NEW
RAM -AA std- Ampx A frm -NEW
Amperex White Logo ECC88 USED
Amperex Orange Globe ECC88 USED
Harma 6922- 6H23n-EB- NOS
Russian unbranded 6H23n-EB NOS
Russian unbranded 6H23n -NOS
Amperex Bugle Boy ECC88-USED-It has been my personal experience over 20 years- this is all in Audio Research SP10, SP8, D115- that the 6DJ8 is always more open and dynamic with a better soundstage than the same make 6922 or 7308. There are tradeoffs in some areas- the Siemens E88CC has the great bass. The 6DJ8 is also the most microphonic by far too ! However from a sonic stanpoint, if I had to name the best of the family it would be the older white labelled Amperex Holland 6DJ8, followed by the Bugle Boy, then the mid 60's Siemens E88CC (6922).
My main concern for our friend new to the type is that they have to first determine which type will survive in their equipment, then consider the sonics. And I believe Rosen's primer can help someone narrow down likely possibilities- it's a shortcut that will lead to fewer expensive experiments- like the probable $500-600 I spent buying 30 6DJ8s for sound before discovering the SP10 eats them in 10-100 hours. Anyway a lot of Rosen's favourites are unobtainable or $XXX! and our friend will have to choose from the more ordinary ones. I do agree completely with your final line, "Use it [Rosen's guide] to expand your horizons rather than to narrow them."
Cheers,
"this is all in Audio Research SP10, SP8, D115-"
Doc B.,Yes, certainly the context of judging tubes is in respect of the euqipment and systems it's used in. On the topic of judging 6DJ8s, I think the Audio Research SP10 is one of the two or three best choices to judge the 6DJ8 as preamp gain tube- in my view the SP10 was the 6DJ8's shining moment- no other preamp made it work for a living like that.
The SP10 uses 12 of them and these, run from a separate chassis, tube regulated power supply. The phono section uses 4- of the 6DJ8s followed by an 8 tube line stage to create 74dB of gain. This gain is enough for medium-low MC cartridges without a step up transformer- but at a cost: it accomplishes this apparently by pushing the gain tubes to the limits- and beyond. The phono tubes have to be just perfect- no detectable noise, non-microphonic, and capable of taking a fairly high current.
Then, the sound of the SP10 is so very revealing- the level of detail and natural timbre istill amazes me- but it also tells you how poor the recordings and your turntable arm are- or o how noisy the tubes are. In short, the SP10 is about as close to a testing device for 6DJ8s as can be- it' pushes them to their highest specification performance and also reveals with intense clarity, whether the tubes are noisy or microphonic, or not very good sounding. I think there is a disconnect between specification and good sound- in my experience, the toughest ones usually do not sound as good as the lower rated.
In judging 6DJ8s, I'm lucky that the SP10 is the performance master in terms of use as gain tubes, then the SP8 uses two as cathode followers, and the D115 power amplifer uses three in the way power amplifers use them. As these three pieces of gear use the 6DJ8 in most ways they're used in audio, since 1985, I've had a kind of 17-6DJ8 test lab !
I once bought a big pile of unbranded Russian 6DJ8s- half were the ordinary rating equal to a 6DJ8, and the other 12 or so were the "-EB" suffix- the equivalent of the 6922- more rugged and rated for 5,000 hours instead of 2,500. These were I think around $4-5 each. I had just gone through a lot of tube fuss with the SP10- the Vice-President of Gold-Aero came to my house and went through 80- that's eight zero- tubes before he was satisfied with the two leading phono Amperex 7308s. Buying the cheap Russian ones was my way to see just what the range of this difficult tube might be. And, in the SP10, the difference from tube to tube was impossibly wide, there was one tube of the 24 or so that was as good as the 2 selected from 80 already selected 7308's, there was another 2 tubes that were acceptable but needed serious damping rings, there were 6 tubes that were so microphonic I could shout at them and my voice would be reproduced in the speakers- literally microphones, and the rest were just far too noisy. Sound quality was pretty terrible, even if the tubes was behaving in other ways.*** I learned again- the 6DJ8 family is just a crazy one -unpredictable, inconsistent, and generally chaos on wheels.
*** -I'm going to put these on Ebay someday for $65 each labelled "NOS/NIB ultra-rare Bambi B 'Trumpet Lad' 7308SL / ECC188SS".
The frame grid tubes must be difficult to make, the frame grid is almost microscopically fine and a floppy thing prone to reasonance. I've heard it said they were not an audio tube, they were actually intended for high frequency stuff- radar and test equipment like oscilloscopes. Today, there's lots of NOS and used 6DJ8s from old oscilloscopes or marked for use in test equipment.
Because of my troubles with the 6DJ8, I was forced to study this big subject, and just when I thought I figured out something about them, the audio world gave up on new production 6DJ8s and is turning to the 6H30. Who knows if new euipment is not using the 6DJ8 will that end efforts to improve new production? I notice the frenzied prices now for the premium ones- and it may be that people intending to keep their 6DJ8 stuff want a lifetime supply at hand of the ones they like. There's millions around but getting the 12 good ones is a long road paved by you throwing gold on the ground in front of you.
Cheers,
Hi Bambi;Thanks for the great inside and info.
I do have a headphone amp that also uses the 6DJ7 and 6922 tubes. Some people have suggested that a 6BZ7 could be used.
Capt. Z.,Actually, I don't know the 6BZ7 or 6BQ7A types. As I've had to deal with some new types recently, I checked into the duncanamps tube data page on Triode Electronics:
http://tdsl.duncanamps.com/show.php?des=6BZ7
- and learned almost nothing except the pinout appears the same, but the Va of the 6922 is 90 while the 6BZ7 is 150. It appears the 6BZ7 and 6BQ7A are not listed as direct substitutes for 6DJ7- (perhaps you mean 6DJ8) or 6922. The two types seem electrically different in some ways,..
On Ebay there are a pile for sale at very modest prices:,
http://search.ebay.com/search/search.dll?from=R40&satitle=6bz7
-so if it works electrically in your headphone amp- and good ones were made, it might be interesting -these are $4 tubes rather than the $35 you might spend for a good 6922.
I bought a McIntosh MR67 recently and it has some types not used very often so I could buy NOS Telefunken, Mullard or Amperex for very reasonable prices- thanks to their not being commonly used. When a Telefunken anything is $10 NOS in the box- it's very comforting in one way- and disconcerting to learn that there will never be anymore of that type made! Even though I may not keep the MR67, I already have at least 2 NOS of any type that isn't made any longer.
I'm always a bit nervous about types and substitutions- I've never heard of the 6BZ7 as a substitute for 6922- and over the 20+ years I've been fussing with the 6DJ8 family, I've heard of people looking for any alternative that will allow them to use something else- preferably less expensive- 7DJ8s, PCC88s had a fad, and people often ask if the 6FQ7 will go.
The preamp tube fad now seems to be the 5751 substitute for 12AX7.
I would make sure- ask the maker - what tubes the preamp can use. Some kinds of gear- and their makers- seem to be more flexible than others for substitutions.
Cheers,
Sorry, I did mean 6DJ8
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