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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Continuation fyi: 6DJ8 have same gain and same posted by warnerwh on September 29, 2004 at 19:55:48:
It might be that when ARC told you a 6DJ8 can always be used in a circuit designed for the 6922 - they were referring to ARC equipment. I don't think they'd intend anything they say to apply to other manufacturers.The voltages Bambi listed are correct as is the hierarchy. The US uses numbers like 6DJ8. Their foreign counterpart is ECC88. The US number for a "special" 6DJ8 is 6922 and the foreign number E88CC.
The 6922 is designed to last 10,000 hours while the 6DJ8 is 5,000. The 6922 is also supposed to be closely matched internally as well as to others coming off the assembly line.
The 7308 is supposed to be a step up in quality from the 6922 and it's foreign number is E188CC. The 7308 has the features of the 6922 but also supposed to be more quiet right off the assembly line. I equate that to being less microphonic too.
All that said - there are still many that do not test or sound as good as others. Most dealers and users will say they've seen tubes that are supposed to be higher quality and are not, while there are tubes that are supposedly lower quality that test great and sound even better.
That's one good reason to only buy from someone you trust to have tested them. I know many people here say test results don't matter - it's how they sound that counts. There is some truth to that, but if you pay top dollar for a tube that's supposed to be quiet and have long life - that's what you should get. It doesn't matter how good it sounds if it dies in a month because it was used or not up to spec in the first place. Although I guess there are some who would say - at least it sounded glorious for a month.
I'm not at all expert in circuit design - but if a unit is designed for 6922 and we're shooting 220 volts at it, using a 6DJ8 in that position might work, but probably with a shorter life. If it does blow - there's no telling what it might take with it.
That's why we make a general statement of substituting a 6922 for a 6DJ8 all the time, but the opposite isn't always true.
Here's some personal thoughts based on the tube specs only. Even though we can use a 6922 in place of the 6DJ8, if the circuit is designed to operate at 130 volts for the 6DJ8, the 6922 may not be getting close enough to it's operating voltage to perform correctly. Although it might work at 130 volts - since it's designed for 220, it might work better if used in a circuit closer to 220 volts.
As a last note - if you search the web for tube data sheets, you'll find them in more than once place. Print and lay them out side by side to see the differences in voltages they'll handle and recommended voltages for circuit design. It's sometimes hard to compare every exact parameter, but for anything I ever wanted to know, was able to plow though things.
I hope I didn't confuse things too much and also hope you can find the sound you're looking for. Fran
"The truth is out there"
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Follow Ups
- Yet more )) Re: Continuation fyi: 6DJ8 have same gain - ruffscruff 22:33:36 09/29/04 (0)
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