I am attaching the text on 6DJ8 family of tubes from "Joe's Tube Lore" (
http://www.audioasylum.com/audio/scr...ubes.html#6DJ8), a well-known and often cited source for good information on tubes. Joe is just a regular poster at audioasylum, but his experience is extensive. These opinions are his alone.
This should help Melos tube-rollers make some choices. Bear in mind that prices he mentions are way out of date. Enjoy.
The 6DJ8, 6922, 7308 Saga - Part 1
Posted by Joe S on March 29, 1999 at 19:59:08:
Well this time I?ll be reviewing substitutes for the ubiquitous Sovtek 6922. That means it is time for 6DJ8s, 6922s, 7308s and a few other odds & sods thrown in for good measure. Once again all the usual caveats apply, so here we go!
A Note on Numbers
The 6DJ8 family was originally developed by Amperex. The first tube in the family was the steel pinned 6DJ8 followed by the gold pinned 6922 and 7308. These latter two were premium versions rated as 10,000 hour life tubes. The 6922 was a premium industrial version and the 7308 was the top of the line guaranteed low noise version. Frankly, I?ve measured & listened to a lot of these and there is no correlation between model # and sound quality. Some of the best sounding tubes in this family are 6DJ8s and some of the worst are 6922s & 7308s. So take each tube on it?s own individual merits rather than judging it by its model number or pin material (gold pins do not necessarily = better sound). The Europeans used different model numbers to identify these tubes, by the way. In their numbering system the 6DJ8 was an ECC88, the 6922 was an E88CC and the 7308 was an E188CC. Oh, by the way, a 7DJ8 is basically a 6DJ8 with a 7 volt heater voltage rather than the 6DJ8?s 6 volt rating. What does 6H23N mean? Who the hell knows! I sure don?t.
Physical Structure:
The late 1950?s and early to mid ?60s tubes in this family had a unique internal structure. Starting at the bottom of the tube and working our way up, first we find the wiring leading up from the pins to the tube?s internal structures. Next is the lower mica spacer it?s a horizontal round disc of mica. This can be round with a serrated or scalloped edge (like a Siemens), or kind of a smooth edge disc with a slightly square shape with rounded corners (like on an Amperex or Sovtek). On top of this are the two vertically oriented plate structures. In this tube type the plates always seem to be painted grey. On top of the plates is the upper mica spacer its just like the lower mica spacer. Up to this point I?ve just described 90% of the 9 pin miniature triodes in the world it?s above this point that things differ. The next structure up is the unique one it?s a horizontal, circular, metal disc supported by two metal bars. I?ve seen & heard this referred to as a shield or a splatter shield. Which name is correct & what is the purpose of this structure? I don?t know, but most all early 6DJ8 family tubes have it. Above this is the getter halo. The halo is usually a metal ring supported by a single metal bar. On some tubes, like very early Amperexes, the getter halo isn?t a ring but instead is a two part metal structure made from wire in the trough shape of the letter D. Tubes with this type getter halo are commonly referred to as D getters. Go figure.
You will often find a different internal structure in what are apparently late production 6DJ8 family tubes from the mid/late ?60s through the ?70s. These tubes sometimes had a simplified internal structure that eliminated the splatter shield / getter halo arrangement. In these tubes two metal bars angle up from the upper mica spacer, almost to a point, with a small metal disc on top. Viewed from the side this metal structure on top of the upper mica spacer looks a bit like the letter A hence the nickname A frame. The other exceptions are some late Siemens 6922s & 7308s that just have a single metal rod rising above the upper mica spacer with a ring shaped getter halo on top a practice copied in the Russian 6922s and 6H23Ns.
Das Toobs:
Enough prologue, on to the tubes! This time out I?m not going to group tubes by quality, instead I?ll take them one at a time by brand & give a brief capsule on each. It had been a while since I listened to some of these guys so I pulled & reviewed my old listening notes, reassembled all the tubes and spent an evening swapping and listening to each pair in my Thor DAC.
Sovtek 6922 (polished steel pins) A bit sterile and lifeless, lacks a bit in dynamics, rolls the deep bass just a trifle and can occasionally sound a bit hollow in the mids. In short Yawn...
Russian 6H23N (steel pins) A Russian tube imported by the good folks at Lamm Audio. It came stock in my amps & is a slight improvement on the Sovtek. While basically similar to that tube, it has a bit more jump, slightly improved deep bass and slightly more palpable mids. The differences are not huge however, so whether or not its worth it to you is an individual decision....
Edicron 7DJ8 (with shield, steel pins) A bit livelier NOS kind of sound than either of the above tubes. A little thin though compared to my favorite Amperexes & Siemens. While this tube represents an improvement over current production tubes I couldn?t live with it (but then I don?t use and AI preamp, so I can run any 6DJ8 I want without worrying about tube life sorry guys!) Ultimately, if I were limited to the first three tubes, this would be my choice.... Also, the source of this tube is a bit questionable. See the Valvo 6DJ8 below for more comments.
Siemens E288CC (with shield, gold pins) More transparent & dimensional with better bass than the Edicron. Also has more palpable vocals and a more lively, real sounding presentation than any of the above. But it?s not even close to Siemens best in this family. Expensive and hard to find too. But the best so far....
Siemens 6922 / E88CC (with shield, gold pins) Now things are getting more interesting. It?s lively, has a palpable & real quality to individual performers with greater dimensionality than any of the above tubes. Warm, lively & transparent with an extended high end. This is a classic tube and an excellent choice in this family if your system is not already over the top in the high frequencies. Often found labeled as a made in West Germany RCA for as little as $20 a pop. An absolute bargain....
Siemens 6922 / E88CC, RCA label (A frame, gold pins) This tube is similar to the earlier 6922 above. Vocals are slightly bigger and slightly more forward, the highs are a bit softer and the overall sound of the tube is a bit warmer. Music is presented with a warm, vibrant acoustic. Very nice & musical, though it might be a bit dull in a system that?s already dark in balance. Another excellent tube...
Siemens 6DJ8 / ECC88, RCA label (with shield, steel pins) Kind of lives in between the two 6922s above. Warm & vibrant, with a slightly forward balance similar to the A frame. Slightly more extended highs than that tube, however. Another very nice tube, frequently found labeled as a made in West Germany RCA....
Siemens CCa (with shield, gold pins) This tube is a premium version of the 6922. It is also one of rarest & most sought after tubes in this family and is priced accordingly when you can find it (not often). Slightly more dimensional, transparent & focused sounding that the Siemens 6DJ8 and 6922s above. It lacks a bit in bass punch compared to those tubes however and is slightly dry sounding in comparison. In short maybe better in some ways, but not a reason for living. In other words, if you are stuck with living with the lesser Siemens tubes don?t worry about what you are missing....
Siemens 7308 / E188CC, RCA label (with shield, gold pins) - Sacrilegious comment time. I prefer the slightly warmer, more vibrant and wetter sound of this tube to the sound of the CCa. Closest sound among the Siemens line to the sound of my favorite Amperexes (coming up soon!)
Siemens 7308 / E188CC, Phillips SQ label (no shield, with getter halo) Warm & transparent. Very close to the shield version above in overall sound quality. Another excellent tube...
Telefunken 6922 / E88CC (with shield, diamond bottom, gold pins) Slightly hollow mids, not as rich as the best Siemens and Amperex. A bit like the Siemens E288CC, though a bit better than that tube. A good tube, but the more common & cheaper Siemens 6922s are much better choices IMO. (Absolutely pounds the Russian tubes, though!)
Sylvania 7308, RCA label (with shield, steel pins) Vocals are sharper & less refined than Siemens, Amperex and the Teles. Not at all a bad tube & better than the Russians in some ways. Lively, vibrant, forward & good bass if a bit of an edge and a little brash. Not a great tube, but a good tube for the price. If your system needs some energy and high frequency oomph and you don?t have much cash this tube is a best buy....
Sylvania 7308, Siemens counterfeit (with shield, gold pins) The morons who did this relabeled counterfeit of a Siemens didn?t even bother to rub off the original made in USA label. An object lesson for care in chasing desirable tubes, there are a lot of fakes and relabels of tubes like the Siemens 7308 and CCa based on the Sylvania & even the Tungsram. I?ll give some hints on how to avoid getting ripped off later in part 2 of this review. This tube is not quite as sharp as the above steel pinned version, but it is still a bit forward. Frankly I prefer the steel pin - this one is missing just a touch of that ones life...
Valvo 6DJ8 / ECC88 (with shield, steel pins) Slightly thin sounding vocals with more air than body. Soft bass, sounds a bit like the Edicron 7DJ8 and that shouldn?t be a surprise this tubes internal construction is identical to that tube (at least on my pair, anyway). These tubes were obviously made at the same plant. In fact, close inspection reveals that every aspect of this tubes physical construction is absolutely identical to the Edicron down to the fat, round top, Russian style bottle and the bright red color on the pins where they pass through the glass. In fact the bottles on both tubes are identical to the Sovtek 6922 so these tubes were either made in Russia or they were made in an Eastern Block country equipped with Russian tooling. Edicron labels their boxes London but that ain?t where either of these came from....
Raytheon 7308 (with shield, steel pins) OK mids, soft on top, good bass. Better than the Russians, but not by tons. As good as the Sylvania 7308 steel pins, but in a different sort of way. Not a great tube, but a good one...
Ediswan CV 5358 (splatter shield, steel pins) Good, palpable vocals, nice upper & mid bass with a nice sense of impact in that region. Good if slightly soft highs. This tube is almost in the same class with the Siemens gold pins if just a bit softer in balance on top...
Whew! Its getting late and I?ve got another dozen tubes to review (including a pile of Amperexes!), some pointers on how to identify the real thing in order to avoid to get ripped off, and a few observations on OEM branding and how that can save you some money In other words way to much to cover now. So until tomorrow night and part 2, good night and good listening.
Stay tuned,
Joe
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The 6DJ8, 6922, 7308 Saga - Part 2
Posted by Joe S on March 30, 1999 at 20:08:00:
Well, hello again! We?re back with the rest of the pack, but definitely not a group of runner-ups. In fact the best of the lot are yet to come along with a few other genuine contenders so lets jump right into the fray...
Mullard 6922 EE88CC, Great Britain (shield, gold pins) This is a Great Britain manufactured tube, not all of Mullards are in this family with a lot of these tubes being sourced form Amperex in Holland. As I understand it, Mullard?s 6DJ8 tube tooling came from Amperex and it looks like it every Mullard in this family I?ve ever seen looks like an Amperex inside down to the smooth edge, slightly square shaped mica spacers. Perhaps as a result this tube owes a lot to the Amperex 6922 family when it comes to sound quality. This guy?s got good bass, nice mids and a wet, ambient soundstage occupied by slightly smaller and images than the Siemens and Ediswans. A nice tube overall though not quite up to the level of the best Amperexes.
Mullard CV 2493, Great Britain (no shield, getter disc, gold pins) This tube lacks a splatter shield with just a small metal wire holding a solid metal disc with dimples around its perimeter above the upper mica spacer. The sound of this tube is very different from the 6922 above, with a less pronounced bass and less vivid highs. It does have a very nice midband, however, combined with a deep & dimensional soundstage. If you find the 6922 Mullards (and Amperex 6922s to follow) too pronounced at the frequency extremes this tube could be a valid choice representing a viable tuning alternative...
Mullard 6DJ8, Great Britain (shield, steel pins) One of my pair of these died a year ago (moment of reverent silence please....) so I couldn?t compare it directly to the others in this shoot-out. Given the vagaries of long distance auditory memory I will not comment on specifics other than to say I remember it as quite good and worth checking out if you get the chance.
Amperex 6922, JAN Orange label, US (shield, gold pins) A little sharp in the upper mids / lower treble. Good upper bass and highs. Vocals lack balance & body A bit disappointing. This tube sorta sucks...
Amperex 6DJ8, Orange globe logo, Holland (shield, steel pins,) Much better than the above tube No comparison in fact. Warm, vibrant, lively, grainless, transparent Amperex sound. Killer tube. Almost as good as my reference Amperex 6922s (coming up soon). I slightly prefer this tube to the best of the Siemens 6DJ8s, 6922s & 7308s.
Amperex 6DJ8, Bugle Boy logo, Holland (shield, steel pins,) Similar to the above tube with a slightly larger soundstage & more ambience, trading off a bit of impact and bass extension. I prefer the globe logo above to this tube by a small margin in spite of this tubes vaunted reputation. But still a good tube...
Amperex 6DJ8, RCA, Holland (A frame, steel pins) - More forward vocals than the Bugle Boy. Sweeter highs too, with bigger, slightly less focused images. A little closer to the Globe logo 6DJ8 overall in character than it is to the BB....
Amperex 7308, Orange globe logo, US (shield, gold pins) More focused and palpable than the Bugle Boy & A frame 6DJ8s. A bit like the Globe Logo Holland 6DJ8 overall. I still prefer that tube to this one but this is still a pretty good tube...
Amperex 7308, JAN, green label, US (shield, gold pins) Very similar to the globe logo 7308 above. Both could use a little more bass kick & body to vocals in my rig, but could represent a useful tuning option in a system where my favorites come across a little too lively and forceful. While this tube is highly recommended by some dealers I think a few of the other Amperexes here slightly best it...
Amperex 6922, PQ, white label, US (shield, gold pins) Another very good Amperex tube. Warm yet lively, focused, grainless and transparent. A winner one of the best. Dynamic with punchy bass to boot....
Amperex 6922, PQ, white label, Holland (shield, gold pins) Slightly more forward midrange than the US version, above, pushing vocals a bit more forward in the mix. Otherwise, very similar. Another winner...
Amperex 6922, PQ, white label, Holland, D getter (shield, gold pins) Another winner. Slightly less midrange emphasis than the round getter halo Holland above, with a bit more life. Good treble extension. An excellent tube...
Amperex 7308 white label, US (shield, gold pins) My favorite 7308 by a small margin. Bass is a bit better than the Holland 6922s. Vocals lack just a touch of body compared to the best Amperex 6DJ8s & 6922s. Still a very good tube overall...
Amperex 6922, USN, white label, US (shield, gold pins) Sounds very much like the US white label PQ. Another excellent tube though it may lack just a bit of that tubes warmth & body, but I?m quibbling here....
Amperex 6922, Mullard, Holland (shield, gold pins) Sounds a lot like a Holland PQ white label. In other words a very nice tube with slightly forward vocals and a lively transparent sound...
Amperex 6922, PQ, white label, US, pinched waist (shield, gold pins) Yeow! My reference tube. An absolutely gorgeous sounding tube with an unusual physical characteristic. The glass of the tube is actually slightly pinched at the about the point of the upper mica spacer. This reduces the tube?s diameter at that point resulting in a subtle hourglass shape. The reason for this was for the bottle to actually clamp the upper mica space at its rounded corners resulting in a more rigid, less microphonic, structure. The result? A tube that defines the Amperex house sound: Lively, transparent & detailed with extended highs, yet absolutely no grain, with a punchy, dynamic bass. Mids? Lucid and palpable, thank you. The best tube in the 6DJ8 family IMO. The only downside? These guys make the rare Siemens CCas look absolutely common in comparison. Cost? If you have to ask.. If I were hunting for a tube almost as good and much more accessible? I?d hunt down some US white label PQs and live contentedly until the gods smiled on me and I lucked into some of these...
Well, that?s it. And there are other Amperexes I haven?t even touched on. While this particular manufacturer made some great tubes in this family, they were offered in an almost bewildering array and while there is a house sound there are some significant sonic differences among them. Now a word on Amperex chronology to help in your searches while I don?t know it all, here is what I?ve been able to piece together so far...
White labels the earliest tubes in this family had white labels. 6DJ8s had the Bugle Boy logo, or just the Amperex name in white, while 6922s were often labeled with the PQ logo in the shape of a shield. I have also seen the 6922 along with the 7308 with just the model number and Amperex name in white. All of these labels were very fragile and rubbed off easily.
Orange globe logos Next up chronologically, these tubes have a reddish orange label printed in a fragile ink that rubs off easily. The logo included the Amperex globe (like the drawing on the yellow & green Amperex boxes) along with the model # and the Amperex name.
Red or green labels these tubes used a thick paint like ink that will not rub off and usually just used text with no logos of any kind. You will often see 1970s JAN (military) tubes printed this way the Green label 7308 US for example.
Why is this important? Well to my ears the best sounding Amperexes were the early ones (generally) meaning all else being equal I?d be chasing white label tubes. Now there are some great globe logos, but some of them just seem to have a bit less of that Amperex magic, but hey that?s me. See what works best for you and chase 'em accordingly. Oh yeah. the best Amperexes were the US & Hollands in my opinion. You will occasionally see other countries of origin for their 6DJ8 family tubes - but IMO these two were the best and that's where I'd spend my money.
Siemens vs. Amperex
So how do the Siemens and Amperex stack up comparatively? Well, to my ears, the Siemens sound just a bit more linear, with just a touch less vibrancy and life and freedom from grain that are the hallmarks of the best Amperexes. The Amperexes sound just a bit more full bodied and lively on top and are a touch more romantic in balance. The Siemens also tend to throw up slightly larger images, the Amperexes slightly smaller, better focused images (but not small - don't get me wrong on this one). Both are exceptional tubes so I wouldn?t hesitate to experiment with either. Which would I be chasing if I were hunting for some great tubes? That?s easy both! :-)
Danger Will Robinson!
Be careful when you chase these guys. The reputation of Siemens & Amperexes precedes them and they are frequent targets for counterfeiters. How do you know if a tube in question is the genuine article? Well, fortunately there are a few basic checks you can perform to differentiate true Siemens & Amperexes from relabeled Sylvanias and Tungsrams.
First, check the top of the tube in question. Siemens & Amperexes always have small ridges in the surface of the glass on top of the tube radiating outward from the nipple. These tubes will have 4 ridges, though sometimes only two of them are easily visible. The concept here is to look down on the top of the tube. The 2 or 4 ridges should divide the circular silver top of the tube in half or into quarters. No ridges? No genuine article pass on it.
Second, check the metal shield above the upper mica spacer. On Siemens & Amperexes it?s circular with two raised rectangular sections on opposite edges of the shield. On most fakes that shield is a perfectly flat disc.
Third, about 90% of Siemens tubes have a 1 or 2 digit number molded into the inside bottom of the tube glass centered between the pins. It can sometimes be very hard to see but it?s usually there. Remember, not all Siemens have it, but if your tube passes test one & two and has the number(s), it's a Siemens.
Fourth, familiarize yourself with the shape of the glass bottle on your stock Sovteks. Note that the top is smooth (no ridges) and rather rounded and the tube is short & large in diameter these traits are common to all Russian tubes in this family. Siemens & Amperexes are only about 80 to 85% of the diameter of the Russian versions and tend to have squarer shoulders on top rather than the rounded top of the Sovtek. You should be able to spot the difference between a Russian and a genuine NOS tube just by the shape & diameter of the glass pretty easily. One warning though Sovteks often (always?) have a number molded into the bottom of the tube between the pins like a Siemens, so know all the checks and don?t depend on just one to verify the tubes origins.
Fifth, if it?s a Siemens or Amperex 6922 or 7308 it will always have gold pins. So will some cheap counterfeits, so gold is no guarantee. But if they aren?t gold its not a Siemens or Amperex, so pass on it.
Brands
Be careful of getting hung up on the brand name printed on the tube. In my experience most Siemens 6DJ8 family tubes you will find in the US are labeled anything but Siemens. Why? Siemens (and most other manufacturers) served as an OEM (original equipment manufacturer) supplying their tubes to many other tube manufacturers. While Siemens made these tubes they were labeled with the name of the company they were supplied to RCA or Phillips for example. Now not all RCAs and Phillips were supplied by Siemens, so that?s where points 1 5 on how to check tubes comes into play. Fortunately, in many cases the tubes are labeled with the county of origin & that can help you identify a tube?s manufacturer. Made in West Germany? It?s usually a Siemens. Made in Holland? Probably an Amperex. Made in the USA? Usually a Sylvania or an Amperex. Oh yeah a useful tip: RCA never made 6DJ8 family tubes. If it?s an RCA and has a ridged top it?s either an Amperex or a Siemens. I?d watch this brand closely if you stumble on it. Many tube dealers will sell lowly RCA 6DJ8 family tubes for $15 to $20 a tube without realizing that there is European made gold inside. Check the tube?s top for ridges, the label for where it was manufactured and if everything checks out, buy it! This is one of the absolute bargain brands in this tube type.
Amperexes were also frequently OEM?d to a variety of manufacturers. Most commonly to Mullard, DuMont, Beckman, Hewlett Packard and a few others. The risk with Amperexes is that they do vary by vintage and model and it?s hard enough to keep that straight among Amperex labeled tubes. Which vintage / version are you buying under another manufacturers brand? Who knows? It?s just pot luck.
My biases
Take my comments within the context of my system which, although CD based, is neither grainy nor euphonically rolled off on top. As a result I value good high frequency extension as it comes through in a clean, grainless and non fatiguing manner. I also like a dynamic, transparent and lucid sound with dimensional images within the soundstage. I also like to have the performers in the room with me so I like a slightly forward, but still non fatiguing balance. If your rig is bright and forward you might want to skew towards the tubes which are softer on top & a little more laid back than my favorites. But frankly, if you are using Sovteks now, this shouldn?t really be a big problem.
Well, that it folks. I hope you find the overview helpful or at the very least thought provoking & hey, if I trashed your favorite tubes - don?t worry about it! It?s just one tube freaks opinion. If they work for you, that?s all that counts.
Good luck!
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