Lecture from
Audiophile tube page
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The 6DJ8 is a twin triode in a small 9-pin miniature glass package, with a very high transconductance for each triode unit. Well made vintage versions of this tube are quite low noise and can be found in many tube preamplifiers, phono preamps, and headphone amplifiers. This tube was also widely used in Tektronix oscilloscopes and other industrial test equipment needing wideband signal amplification. These tubes can tend to be microphonic, so careful selection needs to be considered if using them in high gain stages. This is a frame grid tube, meaning the grid wire is wound around a tiny framework. The grid wire itself is vanishingly thin....thinner than human hair. These tubes were not originally designed for audio use, but more so for test equipment. Therefore, not alot of attention was paid to making this tube as quiet microphonically as possible, and the fine grid wire on the frame can tend to exaggerate the problem, if it exists in the particular tube. The better Western Europe vintage tubes seem to be the best with regards to low microphonics and low noise. Matching these closer than 5 percent is often difficult, as is the case with most vintage tubes, since quantities are rarely found from the same batch or date code. This should not pose a problem for any well-designed preamp circuit.
NOTE: This is a very popular tube, and supplies of the best vintage examples are becoming very scarce. Please hit "reload" or "refresh" on your browser to get the latest version of this page. My stock changes rapidly! One day I may be out of most high end vintage types, and a few days later may have a fresh stock. Check this page often. If you must have a certain type over any other, please e-mail me and I can put it on my buying list for you.
6DJ8:
This is the standard incarnation of this tube. It was made both in the USA and in Western Europe. GE and Sylvania both made USA versions, and are fairly good quality. The GE tubes have an RF shield sprayed on inside the glass, making the inside look dark. This is NOT an indication of a burned out or used tube. RCA tubes were often made by either Mullard or Amperex in Britain or Holland. The most popular NOS vintage tubes are those made by Telefunken, Amperex, Siemens or Mullard, and are usually also labelled ECC88. See the next paragraph for this description.
ECC88:
This is the European designation for the 6DJ8 type tube. It is the same tube as a 6DJ8 and often the tube has both type numbers on it. The popular vintage tubes here are those by Telefunken, Amperex, or Mullard. The Telefunken are said to sound the best, and are the most difficult to find of all of these brands. All Telefunken tubes have a tiny diamond shape molded into the glass on the bottom, and have a very chalky ink on the surface which often is partially wiped off. Beware! These tubes are being reproduced in China, and look like the real thing, complete with diamond mark. The tipoff is the label: the fake labels will not wipe off.
The Amperex can be found with a white label and the treble clef logo (rare), the Bugle Boy cartoon tube logo, Amperex in white ink, and the orange world logo. The orange world logo is the newest, and can be found in both standard "L" bracket top getter, and the rarer (and said to sound better) "A" frame top getter. The A-frame looks like a little metal "A" holding up the getter element on the top of the tube internal structure. I have also seen the A frame getter on some Mullard and Genalex (G.E.C.) tubes. The Bugle Boy is the most popular, almost to being a "designer" label, which has driven the price up and supplies down. See note below about Bugle Boy 6DJ8 tubes. I believe any of the Amperex 1960s and 1970s 6DJ8 tubes are excellent, no matter which one you use. The tubes made with the plain white label (Amperex, DuMont, Hewlett-Packard, Beckman and others but all labelled "Holland") were made in the same factory as the Bugle Boy tubes and sound the same, but are often bargain priced due to low demand. Beware! The Bugle Boy tubes are being reproduced today! The box of the new tubes is even an identical green-and-yellow like the original, but it says "Bugle Boy" on it, and some even show the cartoon tube on the box. Original Amperex tubes NEVER had the words "Bugle Boy", or the cartoon tube, on the box. The Bugle Boy moniker is a slang name that audiophiles coined for the the little cartoon tube on the tube's label. The new tubes have fooled even some seasoned audiophiles! These are junky Chinese made tubes with the old label. The company vending them says they have the original burn-in racks from the old Holland factory. Big deal!! The old burn-in racks are not going to help a crappy tube. Stick with the vintage tubes while you still can!
Mullard 6DJ8 tubes are excellent as well, but are more difficult to find. They often made 6DJ8 tubes for other labels, like RCA, Zenith, and other USA brands. They have several seams molded into the top of the tube.
6922:
This is one of two premium versions of the 6DJ8 tube. First of all, it is the same tube as the 6DJ8, and will work wherever a 6DJ8 is needed. It has premium features such as low noise, low microphonics, and usually a longer lifespan. Sylvania made a version that is JAN military spec without gold pins. Amperex made all of theirs with gold plated pins and most have the PQ shield logo, standing for Premium Quality. See note below about Amperex 6922 and Bugle Boy tubes. Some of the later gold pin Amperex have the orange world logo. I have seen both orange and white PQ logos. Some of the early versions also have a number etched into the glass, like the 7308 tubes. These were also made for other manufacturers, and will have that makers name labelled in white, but these are the same gold pin tubes. Amperex opened a factory in New York to make these for the US military (since the government contract specified only USA constructed products) and cranked these and 7308 tubes out. A "made in U.S.A." Amperex tube is not a fake! In fact, these tubes are really excellent. A few were made in Holland for non-military industrial use, but these are rare. Also rare are the "pinched waist" versions of this tube. This is actually a molding flaw which made the glass bottom slightly fatter around the outside than the rest of the tube, and the center of the tube actually dips inward and touches the metal elements inside. These tubes are said to sound better, but I have no proof of that.
RCA 6922 tubes were made by Siemens in Germany, and also have gold pins. These are great tubes, but are not as plentiful. Since the military and some large industries (Tektronix) bought the Amperex made tubes in huge batches, that is what is on the surplus market today.
E88CC:
This is the European equivalent to the 6922. Telefunken made a fantastic version of this tube, complete with gold pins. Other vintage brands are available, but Telefunken, Philips, Siemens and Mullard are all I have ever seen in several years of tube hunting. There are some types out there, like "Golden Dragon" just to name one, but these are recent manufacture Chinese tubes, and can't hold a candle to the quality of the Telefunken or even any of the vintage 6922 types. There are also some nice USA made military and industrial types available with either gold or standard pins, and even these sound better than the current production tubes, and are usually priced the same or less.
CV2492:
This is a European military (usually British) version of the 6922 / E88CC type vacuum tube. Unlike the US military version, these tubes were never made in the USA. Most of the older examples were made in either the Mullard Mitcham, UK factory, or the Philips/Amperex Heerlen, Holland factory. These are fine tubes that have passed various demanding military specification tests regarding ruggedness, heat and shock resistence, and heater life. Like their civilian/industrial counterparts, they have the four molded seams on the top, heavily plated gold pins, a halo top getter with a splatter shield below it (with slight raised indentations at the 3 and 9 o'clock positions on the shield), and the standard Mullard/Philips factory date codes printed near the bottom of the glass side. Care must be taken, however, when buying these tubes if they are merely identified as "CV2492" tubes. These tubes were made well into the 1980s, and later examples are not as valuable or as desirable as the earlier varieties. Later versions were made in the former Yugoslavia and then in Russia. The Yugoslavia versions can be spotted by their lack of gold pins, and the halo getter mounted low, almost touching the splatter shield. The Russian versions are even easier to spot, as they have a fatter glass bottle, a top mounted cup shaped getter, no top mold seams, and sharp pointed pins which may or may not be gold plated. These are not bad tubes, but should only be worth one half to one fourth of what the UK or Holland made tubes are retailing for. Give the CV2492 a try, the older versions are sweet sounding and long-lived, and are a step up from the garden-variety 6922 / E88CC, and prices are generally a little lower.
E188CC:
A bit rarer than the E88CC, the E188CC is usually found labelled as such by Siemens or Telefunken. Amperex and other makers (Sylvania for example) used the industrial 7308 marking. It is basically the European equivalent to the 7308. The E188CC has gold pins, and is near the top of the 6DJ8 food chain. The Siemens version from the 1960s is quite rare, and is rated by many audiophiles as a jewel on par with the best Cca tubes, or the cryo-treated 7308s. It has low noise to the vanishing point, and a wonderful, airy top end and soundstage. This early version Siemens has a small halo top getter, and is labelled E188CC in white ink. Versions made in the Philips Holland plant are similar, and have the SQ logo. If you find some, grab 'em while you still can!
7308:
This is probably the ultra 6DJ8 type tube commonly available. It has all of the features of the 6922, but the triode sections are also matched to each other, and the tubes all fit within very tight specifications. Therefore, any 7308 should match any other 7308 within the same brand. The Amperex versions were again made in New York, complete with gold pins, and often have a number etched into the side of the glass. Amperex made these for industry as well as the military. The Amperex versions have the PQ label, the military type usually is labeled "USN-CEP", but I have seen versions made for Stromberg-Carlson and Hewlett-Packard, with white ink labels. These all had the numbers etched into the glass, and all are the same tube. There were a few of these made in Holland, but most were made in the USA. The Holland PQ versions have the PQ with stars on either side of the letters, and the words "Premium Quality", where the USA types have the PQ inside of a shield logo. Again, there are some nice vintage USA made standard pin military and industrial types available from Raytheon and Sylvania, just to name a few, and these are quite good at a price currently far below the European vintage labels.
Cca:
Whew, these babies are so scarce there isn't even much info out there about them! Mentioned by audiophiles, usually in a reverent whisper, these gold pinned gems are about as good is it gets in 6DJ8-land. Matched triode sections, low noise screening, 10,000 hr. heater life expectancy, carefully controlled frame grid winding, low microphonics......the list goes on and on. To date, I have only seen Siemens and Telefunken examples of these tubes. I don't believe there were any of these made in the USA. Awesome audiophile tubes!
7DJ8 / PCC88:
This is an unusual tube that must have had a limited range of specific uses. It is virtually identical to the 6DJ8 except for the heater rating, which is 7 volts. I have seen Siemens, Valvo, Telefunken, Philips, Ultron and Matsu****a (Japan) brands of this tube. It probably makes a good sub for the 6DJ8 and may last longer due to the higher voltage heater. Some are labelled with only the "PCC88" and others have both types listed on the label. All seem to be good quality. The Japanese factory was set up by Mullard, and these tubes even flash orange at the bottom of the filaments when first energized, like most European triodes do. Most of the European types were made at the Munich Siemens factory, the Hamburg Valvo factory, the Heerlen Holland Amperex Factory, or the Blackburn, UK Mullard factory. These sound just like the best 6DJ8 tubes, the German tubes being mostly neutral, and the Dutch and British tubes having a touch of midrange warmth. You may want to try a 7DJ8 for the longer heater life in a 6.3 volt circuit, and the lower price!
A Note About Amperex 6922 and Bugle Boy Tubes:
Thanks to a USA electronics company that shall remain nameless, there is much confusion in the tube world about Bugle Boy tubes. I will try to clear up the confusion as briefly as possible. This company bought the rights to the name Amperex, the name Bugle Boy, and the rights to the cartoon tube logo. This new owner is NOT Dutch Philips or North American Philips, who originally owned Amperex and made the vintage tubes that audiophiles want. When I mention "Amperex Holland" or "Amperex USA", I refer to the Dutch and North Amperican Philips owned companies (now defunct) that made tubes, now in demand by audiophiles, up until the late 1970s. There are 6922 AND 6DJ8 tubes being sold today under the name Amperex Bugle Boy, and they even come in a green and yellow box like the original Amperex tubes. THESE ARE NOT AMPEREX TUBES AT ALL, AND THEY ARE NOT NOS. They are either relabeled Chinese or late production JAN Sylvania tubes. These fakes contain several errors:
1. Amperex Holland or Amperex USA NEVER used the words "Bugle Boy" on their tubes or boxes.
2. Genuine NOS Amperex tubes NEVER had the cartoon Bugle Boy printed on the tube box.
3. Amperex Holland or Amperex USA NEVER made a 6922 (E88CC) tube with the Bugle Boy cartoon on either the glass or the box. They also NEVER made a 7308 or E188CC with the Bugle Boy on the box or glass. In this family of tubes, only the 6DJ8 had the cartoon tube on the glass, but again, never on the box.
4. Again, there IS NO SUCH THING as a genuine Amperex Bugle Boy 6922 or 7308 tube. This bears repeating!
5. We stock the real NOS 1960s and 1970s Amperex (Holland and USA made) 6922 and 7308 tubes. They either used the white label or the orange globe logo label, with either the PQ (premium quality) logo, or were military USN/CEP or JAN labeled. We also stock the real NOS Holland 6DJ8 Bugle Boy tubes from the 1960s. Amperex did not make these in the USA. These DO have the cartoon boy on the label, but NEVER had the words "Bugle Boy" printed on the box or the tube glass.
6. Nearly all of the NOS 1960s and 1970s real Amperex tubes have the factory date codes on the side of the glass. The fakes do not.
