Page 1. Page 2. Page 3. Page 4. Page 5. Page 6. Page 7. Page 8. The is described as being for use in cascode circuits and as a multivibrator and cathode follower in References: Datasheet & private correspondence. E88CC-TK TUBE DATA SHEET. Mechanical. Also known as the , the E88CC was originally targeted for test equipment and radar. The E88CC has.
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ACHiPo on 15 Jan ACHiPo on 17 Jan Steve Industry Participant Posts: E55l2 on 25 Jan What do you or those costumers mean with tube life? To know the tube life you have to measure the tube S, Ri, mu etcetera Quote from: Steve on 25 Jan E55l2 on datashee Jan Steve on 26 Jan In Europe, where i live, the equivalent for an is the E88CC. At least people who care about good performance don’t like that. My concerns are the safety catasheet case a catastrophic failure of the valve occurs, the datahseet good performance are acceptable to me.
That depends on the circuit specially if it is dc coupled datashheet the components also but it is possible datasheet this can happen. FullRangeMan on 26 Jan Steve on 27 Jan ACHiPo on 27 Jan RCA have a special dafasheet of tubes, the “red base”.
I’ve gotten used to a very nice solid state pre, and then when that died, listened straight from the DAC to the amps, so maybe this is what it always sounded like, but it doesn’t seem right and I’m not that crazy about it.
So my question is–do s these are 7DJ8s need time to warm up, burn in, or otherwise sound right? My preamp is a Sonic Frontiers Line One.
OPERATING POINT LIMITATIONS
IF, the manufacture’s 6292 AC line voltage for the preamp is, say, Vac and the users house mains voltage is Vac what would the preamp’s power transformer heater secondary winding voltage measure? How hard did the designer of the preamp drive the recommended tube? 692 seems with that information it would be pretty easy to figure out what I’m giving up in performance by running the heater voltage below its designed level.
I ran a test using a used EH tube.
For the test a Hickok a tube tester was used. First I checked the tube for its’ Mutual Conductance at the 6. For what it’s worth there is eatasheet tube life test that can be preformed on a used tube where the filament voltage is datqsheet in the same manner as I did in my test above.
So it is better not to use 6v but a little higher. 692 is no problem supplying 6. However, there are extenuating circumstances involving heavy plate current and increased frequencies into the high MHz, and depending vatasheet the tube, in which transit time becomes a problem. For general public, consider evaporation of water cools the remaining container of water. The lower the plate current, the less the cathode is cooled by electrons leaving.
I run my tubes in the 11A less than typical plate current. I would venture a guess that one of two reasons apply. I do in my preamps, but amplifiers, expecially the output tube, this is a consideration that needs to be addressed.
As far as transconductance being reduced, reduced transconductance will increase the plate resistance, thus lowering the high frequency response. Whether the reduction in hfr will affect one’s perception will depend upon several factors. Cheers Steve Logged jea48 Jr. Quote For what it’s worth there is a tube life test that can be preformed on a used tube where the filament voltage is decreased in the same manner as I did in my test above.
To know the tube life you have to measure the tube S, Ri, mu etcetera Simply perception, which in the end is all that counts. This string will be long gone. If the filament or cathode is operated continuously with a higher voltage than that recommended, some of the coating material is evaporated and permanently lost, thus reducing the life of the valve.
Moreover, some of this vapour tends to deposit on the grid and give rise to what is known as grid emission when the grid itself emits electrons and draws current commonly known as negative grid current If the filament or heater is operated for long periods at reduced voltages, the effect is a reduction in emission, but no damage is generally done to the valve unless the cathode currents are sufficient to exhaust the “space charge.
At less filament voltage, the carbonates evaporate less, so grid contamination is less over time, a plus. Jim Jim, Great info! It seems to support Brent Jesse’s and Kevin’s position that 7DJ8 tube life could be longer at the lower heater voltage, but FRM and E55’s contention that it’s not good practice are supported as well.
Kinda makes me want to sit around the fire and sing Cumbaya.
Logged Steve Industry Participant Posts: The only reason I am posting now is to prevent the public from being misled with false information. Please reread my last posts, as I have some 58 years actual experience 45 years since collegeincluding college lab and my own personal lab, and have explained some basic aspects of cathode datashset principles.
Simply reading a “specification” sheet of typical operation does not cover all aspects of operation, since spec sheets only cover very basic operating principles, not exhaustive by any means. For instance, no information is given on how the cathode actually works, space charge etc. Next, I am not datashee take sides, to explore operating a 7. I am not sure where you come up with the hours, except to say that covers power tubes as well, datassheet is under manufacturer’s warranty.
However, I have seen hundreds, if not thousands of RCA and other brand 6dj8s that were under high stress that measured nice specs after years and thousands of hours of use.
Manufacturer’s specs will be conservative. My customer was reviewer Rich Weiner who wrote for Bound for Sound. Of course he is very careful about the sound of his reference system. However, over the years I have not keep a time clock on tubes hours.
You can read some reviews of one of my poor designs here. Please pardon me if I have crossed the line of civility. Cheers Steve Quote Steve said: For their ruggedness I use EH tubes for the input and driver tubes. One matched pair low noise per channel. The input and driver tubes for each channel have to be biased.
Here is the bias adjust procedure for the VT50 http: See numbers 4 and 5 for setting the input and driver tubes plate voltage on the PDF Link provided. 622 can’t set the two plate voltages of each tube individually. RV1 trim pot is for the input tube and RV3 is for the driver tube. Next read note 7 And there is the rub.
Unless each section of the tube is closely matched good luck meeting 7’s requirements. I am not going to name the Vendor I bought the last closely matched low noise quad of EH tubes from. I will say he is datashest known and respected. I have bought from him before. His close matching of the last set of tubes I bought from him might work as driver tubes in other audio circuits just fine, but not in an ARC VT50 amp.
Here are the tube vendor’s test readings of some of the his tubes markings on each tube box. Section 1section 2 No way this tube could be biased in the VT50 as a driver tube let alone an input tube. And yes I tried. With this tube the difference in imbalance voltage between the two plates was less than 1Vdc. I take that as a given when dealing with a well known and well respected tube vendor.
Not knowing how it would turn datasehet I tested several other used, that tested like near new, EH tubes in a Hickok a Mutual Conductance tube tester.
These tubes were also bought as closely matched low noise tubes from well respected tube vendors. What I discovered was for a tube whose sections MICROMHOS tested very close or the same that tube was the best candidate for achieving the best equal vatasheet voltage for the plates of each section of the dual triode tube.
Note, not so for the VT mrk 3 amp, different circuitry. Could you please explain why? Differences in Plate resistance? Jim My dqtasheet to the OP for getting off topic. Steve, You’re playing well within bounds as far as I’m concerned, and I’m learning a heck of a lot in the exchange, so thank you. Jim, I don’t have any issue with you tagging onto this thread, but you might want to start another thread just so folks with a similar question in the future might be able to more easily find the datasheeh.