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
href="mailto:brentjes@audiotubes.com">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. The USA made
military white label types have been rated "Best of All", over other 7308, 6922
and even Cca tubes, in several well-documented 6922/7308/Cca listening tests.
Therefore this particular type is becoming scarce and prices are rising. 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 Matsushita (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! |
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