6922 vs. 6DJ8 vs,7308

Are these tubes interchangeable? I have all tubed systems, and the time has come for me to replace them with newer ones. Can I switch one from the other? What is their difference in terms of voltage use, quality, etc...
thanks to all of you who are techno scholars, you have been super helpful!!
They are all Interchangable. I have found the 7308 to be a nice upgrade over 6922.
A simple, brief answer - yes, they are all interchangeable with absolutely no problems. Again, to be brief, the pecking order is 6DJ8, 6922, 7308 i.e. good, better, best.

Now is you want to find out which is the best brand of the above noted variants, that is a very complex and very opinionated question in which we will need to know more about your system set-up, application, and sonic objective.
Below are a number of sites that give the info you are looking for. Pretty self explanitory. Look at the first three sites under tube data for an hour or so. You will find them very helpful if your getting into tubes.

Section VI: Tube Numbering and Tube Data, Amp Schematics, Glossaries/Dictionaries.

Tube Numbering explained:
*) Tube Numbering Systems (from Frank’s site) http://home.wxs.nl/~frank.philipse/frank/tubnum.html
*) Philip, Valvo & Mullard Valve Coding: http://www.cs.helsinki.fi/u/oheinone/valves/pvm-coding.html
*) Tube Numbering (from MachMat Site) : http://www.machmat.com/info/index.htm
*) Russian encoding system: http://www.arrakis.es/~igapop/russianotes.htm

Tube data:
1) Duncan Amps: http://www.duncanamps.co.uk/cgi-bin/tdsl3.exe/searchform
2) Frank’s Tube Data Page http://frank.nostalgiaair.org/index.html
3) Triode Electronics Tube Data Sheets: www.triodeel.com/tubedata.htm
4) Radau5”s tube data sheets: http://www.radau5.ch/valves.html
5) Tubebuilder Tube Data: http://www.tubebuilder.com/tubedata.html
6) Vacuum Tube Valley: http://www.vacuumtube.com/FAQ.htm.
7) Svetlana, Tube Dictionary: http://www.svetlana.com/docs/dictionary.html
8) Audiomatica, Tube Directory: http://www.mclink.it/com/audiomatica/tubes/home.htm
9) National Valve Museum’s list of Equivalents: http://www.valve-museum.org/
10) 4Tubes. http://www.4tubes.com
11) Tube Collector’s Association: http://www.tubecollectors.org/
12) Mach-Mat: http://www.machmat.com/sheet/index.htm
13) Kytelabs Tube infobase: http://www.qsl.net/dl7avf/roehren/roehren.html#TOC
14) An Intro to NOS tubes: http://www.soundstage.com/tubeor/tube.htm
15) Western Electric Archives: http://www.westernelectric.com/spec_sheets/we_spec_sheets.htm
16) Tom Jennings: http://www.wps.com/archives/tube-datasheets/index.html
17) Åke’s TubeData: http://www.tubedata.com/

I remain,
Hey "Clueless" after that very well crafted post, you should seriously consider changing your login ID :=)
Nobody with moniker "Clueless" can post a list like that. That's it--I'm having A-gon revoke your moniker--it's just not working.
European 6DJ8 family equvilent 6DJ8-ECC88, 6922-E88CC,
Hey thanks. It's part of a larger "guide" to online DIY tube info I have put together. If you find that list helpful you might find some of the rest helpful. Drop me an e-mail (You cant' send attachments thru Audiogon email system)with your address and I'll send ya the rest. It's convenient because it's a word doc with live links.

I remain,
If you read the tube manuals, there are differences in specs between the 3 types. Generally, for use in audio circuits, they are pretty interchangable. But not identical.

Add this to Clueless' list: http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html#6DJ8
A circuit that requires a 7308 may not be able to use a 6DJ8. A circuit that can use a 6dj8 can use a 7308. They are electrically different.
I would caution against the over reliance on any "pecking-order" with respect to "good-better-best" with these tubes. Aside from synergy with particular components, there is variability between brands and even between types within brands. For instance, I had a set of military-grade Telefunken 6dj8's that were much sweeter and less microphonic than MANY of the 7308's, 6922's, and Cca's that I also tried. Also, don't let anyone fool you into thinking that all gold-pins are better than all steel pins.
100% aggree with 4yanx as to a pecking order of quality as it pertains to sound quality - it depends.