rafafredd
Well-known member
Yes, it would be great to have the files, as I didn´t got any boards...
It's Wed Again
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CJ
Well-known member
6DJ8:
Originally designed for low noise RF applications around 1948.
Developed simultaneously by Tungsram UK engineer John Sargrove as the UA-55, a dual-section beam tetrode for audio power applications. It was a commercial failure. It was sensitive and was also designed to operate efficiently, giving 1 watt on only 90 volts plate power. This was made possible by the close spacing that frame grids allow.
The credit for the frame grid usually goes to J.A Morton and R.M. Ryder of Bell Labs. They introduced the 416A triode in the winter of 1949 meeting of the AIEE. This remarkable and odd looking metal tube was intended as a microwave RF amplifier for telephone long distance relay equipment. The extremely fine pitch of the grid wires, 1000 per inch, and their 0.6 mil spacing from the planer cathode were records at the time.
At the same time, some more conventional miniature glass tubes were introduced by Bell Labs and manufactured by Western Electric. Besides the 416A, WE also produced the 404A pentode, the 417A triode, 418A power tetrode, 435A tetrode, 436A power tetrode and 437A triode during the 1948-1951 period.
Up until that time, there were limits on the capabilities of conventional tube manufacture. To get low noise, the tube has to have high transconductance; and to use it at UHF or higher frequencies, the tube structure has to be small. The limit given for conventional tube manufacture is usually the 6AK5 pentode, with a rated transconductance of 5000 to 5500 umhos and a grid plate capacitance of 0.02pf. Raytheon's 6AH6 bettered that in 1946, reaching a gm of 9000 umhos with some difficulty.
Special tubes were developed for UHF before World War 2, they were usually made as physically small as possible to reduce capacitance and parasitic inductance, but were not outstanding in transconductance. This family includes the Western Electric "doorknob" tubes such as the 316A, 713A and 717A; RCA's "acorn" series, and the 9000 miniature series. Many were used in early FM broadcast receivers and in UHF military radio equipment of the war. RCA pushed this as far as it would go with the 6J4 in 1944, a uhf triode with Gm=12,000 umho. The 6J4 was not very successful. It apparently was very difficult to make, and a high infant mortality rate may have been the reason for the high price of $8.35. Imagine paying 100 dollars today for a small RF transistor-it had better have special characteristics for that price!
The RF performance of such type was acceptable, but not enough for such critical applications such as microwave telephone systems and specialized military equipment. AT&T wanted to expand long distance networks after the war, and microwave was seen as the only cost effective way of doing it. So the development of frame grid tubes was sparked by telephone application more than any other. RF transistors were awful until the 1960's, and so frame grid tubes like the venerable and popular 417A ruled the VHF and UHF bands. Some high performance 2 meter amateur receivers and converters of this era used 417A front ends.
The race for more transconductance continued through the 1960's. GE held many of the records with their ceramic planer triodes, starting with the 7077 in 1954 (Gm=10,000) and moving all the way up to the 7768 (Gm=50,000) and the 8917 (Gm=65,000), which has been unbeatable since the late 1960's except by some bipolar transistors and very exotic MOSFETs.
I should also note that tubes are much more linear than MOSFETs. Tubes follow a 3/2 power relationship, while MOSFETs follow a square law and bipolar transistors follow an exponential relationship. The transconductance of the transistors varies considerably with drain and collector currents. as well as with the ambient tempter, while tubes vary in transconductance only moderately with plate current, and hardly at all with tempter. The input capacitance of transistors, (especially MOSFETS) changes dramatically with bias. In spite of 40 years of aggressive R&D on semiconductors, frame grid tubes remain very close to the world's best transistors.
And frame grid tubes have other advantages over the current crop of semiconductors: high tolerance of ESD and EMP, wider dynamic range due to high voltage operation, and a tendency towards lower distortion. Even so, the mainstream electronics industry has declared tubes obsolete. A test setup to show that the best GaAs FET was noisier than the 417A was only able to show a 0.6db difference.
Some of the R&D for frame grid tubes rubbed off onto power types like the Sylvania 8417 audio beam power tube (Gm=23,000). This tube had conventional construction but incorporated some special manufacturing processes derived from frame grid methods. Sylvania developed a few frame grid power tubes for TV sweep and audio applications. This also included the 6FG6 and 6DY7. By the 1960's, frame grid tubes became common in TV sets. Single-sectioned variants of the 6DJ8 such as the 6EH5, 6GH5, etc, replaced the dual triode cascode as the front end RF tube. Frame grid pentodes such as the 6EH7, 6EJ7 and 12GN7 were used for IF and video amplifiers.
The 6DJ8 was introduced in 1957 by Amperex, the American division of Philips. It was developed by Phillips in Holland, under the European standard designation ECC88, and intended as a cascode amplifier for television VHF and UHF tuners, nothing more. The series string 7DJ8/PCC88 was also introduced at this time. It was apparently a higher performance descendant of the 6BQ7 dual triode, which was also intended for RF cascode circuits. The 6DJ8 became a popular type, especially when the engineers at Tectonic discovered it. They found that it was consistent enough for their oscilloscopes, and gave excellent pulse fidelity. So it can be found in the sweep and vertical amplifiers of Tek's major tube scopes, starting in 1959. Since the 6DJ8 was low in cost, it also ended up in a great deal of military and commercial radio equipment.
It first appeared in home hi-fi equipment as a front end for FM tuners. The classic Fisher FM-90X tuner was the first to use the 6DJ8 in 1957, although the tube was a developmental unit at the time. Fisher called it a "Gold Cascode" and for a time it was exclusive to Fisher. But everyone wanted this hot tube, so it was issued a standard RETMA code:6DJ8. For many years, Amperex/Phillips was the major source, with Seimens, Telefunken, GE and Sylvania weighing in with their own versions later.
Premium 6DJ8 types appeared during 1959 to 1961. The 6922 was an industrial version, introduced by the USA by Amperex. The rare and expensive 6922-PQ version was from Amperex, with gold plated pins an d having the two triodes in the glass envelope carefully matched. This was an example of a "super premium", although this was done by the original manufacturer and for use in critical applications, not audiophile equipment. Many PQ's were used by Los Alamos Laboratory in custom built electronics. Seimens introduced their own "super 6DJ8" at the same time, in the form "CCa". Apparently this was a contraction of the original European designation for the 6922, E88C, with the "a" indicating a premium version. In 1961, Amperex introduced a special version, the 7308. It was the first to have guaranteed low microphonics, suggesting use as the input stage in high gain audio as well as RF preamps.
Nevertheless, these tubes were used primarily in VHF receivers, TV sets, test equipment and nuclear instrumentation. One of the first audio uses for the 6DJ8 was the Marantz 9 power amp of 1960. This was one of the first "high end" audiophile amps ever made, long before the term "high end" existed. Its use in the 9 guaranteed that the 6DJ8 would have a certain cachet with audiophiles. The 9 is now a rare collector's item. so popular in Asia that Marantz recently reintroduced it, with the same circuitry and most of the same components.
In the late 1970's, Audio Research introduced the SP-6E preamp with two 6DJ8's in the phono stage. This was followed by th SP-8, then by the massive SP-10, which used them in all the gain stages. Since then, the 6DJ8 has pushed the 12AX7 out of most high end pre-amps. Currently, the 6DJ8 (or the 6922-the two types are basically interchangeable) is found in preamps and other equipment by Audible Illusions, Sonic Frontiers, Melos, Dynaco, Balanced Audio, Music Reference and to many others to mention.
Construction:
Unlike the conventional tube grid, the frame grid is just what it seems. Rather than being wound around a swaged pair of posts, very fine wire is wound onto a rectangular frame of stamped metal, often molybdenum. This gives very consistent grid structures, which allows the grid to be placed closer to the cathode, thus yielding higher transconductance.
The extreme consistency of frame grids also tends to produce the most beautiful, consistent plate curves possible, which in turn tends to result in lower distortion.
Credit Eric "The Tube God" Barbour for that fabulous research.
Originally designed for low noise RF applications around 1948.
Developed simultaneously by Tungsram UK engineer John Sargrove as the UA-55, a dual-section beam tetrode for audio power applications. It was a commercial failure. It was sensitive and was also designed to operate efficiently, giving 1 watt on only 90 volts plate power. This was made possible by the close spacing that frame grids allow.
The credit for the frame grid usually goes to J.A Morton and R.M. Ryder of Bell Labs. They introduced the 416A triode in the winter of 1949 meeting of the AIEE. This remarkable and odd looking metal tube was intended as a microwave RF amplifier for telephone long distance relay equipment. The extremely fine pitch of the grid wires, 1000 per inch, and their 0.6 mil spacing from the planer cathode were records at the time.
At the same time, some more conventional miniature glass tubes were introduced by Bell Labs and manufactured by Western Electric. Besides the 416A, WE also produced the 404A pentode, the 417A triode, 418A power tetrode, 435A tetrode, 436A power tetrode and 437A triode during the 1948-1951 period.
Up until that time, there were limits on the capabilities of conventional tube manufacture. To get low noise, the tube has to have high transconductance; and to use it at UHF or higher frequencies, the tube structure has to be small. The limit given for conventional tube manufacture is usually the 6AK5 pentode, with a rated transconductance of 5000 to 5500 umhos and a grid plate capacitance of 0.02pf. Raytheon's 6AH6 bettered that in 1946, reaching a gm of 9000 umhos with some difficulty.
Special tubes were developed for UHF before World War 2, they were usually made as physically small as possible to reduce capacitance and parasitic inductance, but were not outstanding in transconductance. This family includes the Western Electric "doorknob" tubes such as the 316A, 713A and 717A; RCA's "acorn" series, and the 9000 miniature series. Many were used in early FM broadcast receivers and in UHF military radio equipment of the war. RCA pushed this as far as it would go with the 6J4 in 1944, a uhf triode with Gm=12,000 umho. The 6J4 was not very successful. It apparently was very difficult to make, and a high infant mortality rate may have been the reason for the high price of $8.35. Imagine paying 100 dollars today for a small RF transistor-it had better have special characteristics for that price!
The RF performance of such type was acceptable, but not enough for such critical applications such as microwave telephone systems and specialized military equipment. AT&T wanted to expand long distance networks after the war, and microwave was seen as the only cost effective way of doing it. So the development of frame grid tubes was sparked by telephone application more than any other. RF transistors were awful until the 1960's, and so frame grid tubes like the venerable and popular 417A ruled the VHF and UHF bands. Some high performance 2 meter amateur receivers and converters of this era used 417A front ends.
The race for more transconductance continued through the 1960's. GE held many of the records with their ceramic planer triodes, starting with the 7077 in 1954 (Gm=10,000) and moving all the way up to the 7768 (Gm=50,000) and the 8917 (Gm=65,000), which has been unbeatable since the late 1960's except by some bipolar transistors and very exotic MOSFETs.
I should also note that tubes are much more linear than MOSFETs. Tubes follow a 3/2 power relationship, while MOSFETs follow a square law and bipolar transistors follow an exponential relationship. The transconductance of the transistors varies considerably with drain and collector currents. as well as with the ambient tempter, while tubes vary in transconductance only moderately with plate current, and hardly at all with tempter. The input capacitance of transistors, (especially MOSFETS) changes dramatically with bias. In spite of 40 years of aggressive R&D on semiconductors, frame grid tubes remain very close to the world's best transistors.
And frame grid tubes have other advantages over the current crop of semiconductors: high tolerance of ESD and EMP, wider dynamic range due to high voltage operation, and a tendency towards lower distortion. Even so, the mainstream electronics industry has declared tubes obsolete. A test setup to show that the best GaAs FET was noisier than the 417A was only able to show a 0.6db difference.
Some of the R&D for frame grid tubes rubbed off onto power types like the Sylvania 8417 audio beam power tube (Gm=23,000). This tube had conventional construction but incorporated some special manufacturing processes derived from frame grid methods. Sylvania developed a few frame grid power tubes for TV sweep and audio applications. This also included the 6FG6 and 6DY7. By the 1960's, frame grid tubes became common in TV sets. Single-sectioned variants of the 6DJ8 such as the 6EH5, 6GH5, etc, replaced the dual triode cascode as the front end RF tube. Frame grid pentodes such as the 6EH7, 6EJ7 and 12GN7 were used for IF and video amplifiers.
The 6DJ8 was introduced in 1957 by Amperex, the American division of Philips. It was developed by Phillips in Holland, under the European standard designation ECC88, and intended as a cascode amplifier for television VHF and UHF tuners, nothing more. The series string 7DJ8/PCC88 was also introduced at this time. It was apparently a higher performance descendant of the 6BQ7 dual triode, which was also intended for RF cascode circuits. The 6DJ8 became a popular type, especially when the engineers at Tectonic discovered it. They found that it was consistent enough for their oscilloscopes, and gave excellent pulse fidelity. So it can be found in the sweep and vertical amplifiers of Tek's major tube scopes, starting in 1959. Since the 6DJ8 was low in cost, it also ended up in a great deal of military and commercial radio equipment.
It first appeared in home hi-fi equipment as a front end for FM tuners. The classic Fisher FM-90X tuner was the first to use the 6DJ8 in 1957, although the tube was a developmental unit at the time. Fisher called it a "Gold Cascode" and for a time it was exclusive to Fisher. But everyone wanted this hot tube, so it was issued a standard RETMA code:6DJ8. For many years, Amperex/Phillips was the major source, with Seimens, Telefunken, GE and Sylvania weighing in with their own versions later.
Premium 6DJ8 types appeared during 1959 to 1961. The 6922 was an industrial version, introduced by the USA by Amperex. The rare and expensive 6922-PQ version was from Amperex, with gold plated pins an d having the two triodes in the glass envelope carefully matched. This was an example of a "super premium", although this was done by the original manufacturer and for use in critical applications, not audiophile equipment. Many PQ's were used by Los Alamos Laboratory in custom built electronics. Seimens introduced their own "super 6DJ8" at the same time, in the form "CCa". Apparently this was a contraction of the original European designation for the 6922, E88C, with the "a" indicating a premium version. In 1961, Amperex introduced a special version, the 7308. It was the first to have guaranteed low microphonics, suggesting use as the input stage in high gain audio as well as RF preamps.
Nevertheless, these tubes were used primarily in VHF receivers, TV sets, test equipment and nuclear instrumentation. One of the first audio uses for the 6DJ8 was the Marantz 9 power amp of 1960. This was one of the first "high end" audiophile amps ever made, long before the term "high end" existed. Its use in the 9 guaranteed that the 6DJ8 would have a certain cachet with audiophiles. The 9 is now a rare collector's item. so popular in Asia that Marantz recently reintroduced it, with the same circuitry and most of the same components.
In the late 1970's, Audio Research introduced the SP-6E preamp with two 6DJ8's in the phono stage. This was followed by th SP-8, then by the massive SP-10, which used them in all the gain stages. Since then, the 6DJ8 has pushed the 12AX7 out of most high end pre-amps. Currently, the 6DJ8 (or the 6922-the two types are basically interchangeable) is found in preamps and other equipment by Audible Illusions, Sonic Frontiers, Melos, Dynaco, Balanced Audio, Music Reference and to many others to mention.
Construction:
Unlike the conventional tube grid, the frame grid is just what it seems. Rather than being wound around a swaged pair of posts, very fine wire is wound onto a rectangular frame of stamped metal, often molybdenum. This gives very consistent grid structures, which allows the grid to be placed closer to the cathode, thus yielding higher transconductance.
The extreme consistency of frame grids also tends to produce the most beautiful, consistent plate curves possible, which in turn tends to result in lower distortion.
Credit Eric "The Tube God" Barbour for that fabulous research.
Great info!
Thanks, mr. Jenrick!
Jakob E.
Thanks, mr. Jenrick!
Jakob E.
NewYorkDave
Well-known member
CJ, that isn't your writing style! At least give credit to whoever wrote that, will ya? :razz:
CJ
Well-known member
Ahh c'mon, let me be a poser genius for at least one day! :razz:
Credit Eric "The Tube God" Barbour for that fabulous research.
:guinness:
Got listening tests and distortion specs for a zillion DJ8's if interested.
Credit Eric "The Tube God" Barbour for that fabulous research.
:guinness:
Got listening tests and distortion specs for a zillion DJ8's if interested.
electronaut
Well-known member
[quote author="CJ"]Eric "The Tube God" Barbour[/quote]
What ever happened to that guy? Seems like his name was on a bunch of great articles for years, then something happened to Svet la na and I never saw his name around again...
-E.
What ever happened to that guy? Seems like his name was on a bunch of great articles for years, then something happened to Svet la na and I never saw his name around again...
-E.
CJ
Well-known member
I don't know. His web site is down and he hasn't answered emails for months.
Maybe he had to re-locate to find work.
When he was moving out of his Sevetlana office in Portola Valley, he told me to come over for all the free tubes I could carry. Like an idiot, I never made it over.:evil:
Sevetlana really screwed him over. Then they went out of biz altogether. What a waste.
Charlie Kittleson, the VTV editor has moved out of the Bay Area.
I did have to type that from the article, Seth!
And it was small print.
Maybe he had to re-locate to find work.
When he was moving out of his Sevetlana office in Portola Valley, he told me to come over for all the free tubes I could carry. Like an idiot, I never made it over.:evil:
Sevetlana really screwed him over. Then they went out of biz altogether. What a waste.
Charlie Kittleson, the VTV editor has moved out of the Bay Area.
I did have to type that from the article, Seth!
And it was small print.
Cainester
Well-known member
Were the '47 PCB's ever shipped?
Caine
Caine
ciminosound
Well-known member
Isn't Eric involved with Metasonix, the tube synth company?
CJ
Well-known member
Yes, at least in the past. Don't know whats up with Mr. Barbour lately.
