[EDS_]

Is the pin layout different?
A buddy claims he can substitute GE Jan 7044/5687s into a circuit designed for 6922s.  I know this will not work and might damage the tubes and or his pre-amp.

Help!

[Gordy]

Here's the data sheets for both... 

http://www.nj7p.org/Tube4.php?tube=6922

http://www.nj7p.org/Tube4.php?tube=5687

[EDS_]

Here's the data sheets for both... 

http://www.nj7p.org/Tube4.php?tube=6922

http://www.nj7p.org/Tube4.php?tube=5687

Thank you!

That certainly will not work.

[JoshK]

Yes, that is a no!  Damage will ensue.  They are not pin compatible.

Actually, taking a closer look at it, it isn't clear whether damage will always occur.  If the circuit he is using only uses Triode 1 from each tube then, apart from optimality, things will work.  Triode 2 though is very different from 6922 to 5687.  This would likely result in severe failure. 

[EDS_]

Yes, that is a no!  Damage will ensue.  They are not pin compatible.

Actually, taking a closer look at it, it isn't clear whether damage will always occur.  If the circuit he is using only uses Triode 1 from each tube then, apart from optimality, things will work.  Triode 2 though is very different from 6922 to 5687.  This would likely result in severe failure. 

I'm showing my arse here - wouldn't a 5687 fail to "warm-up". Looks to me like the 5687 needs more heater amperage than 6922 supporting circuitry should/would supply?

[JoshK]

That depends on what the heater PSU can supply. If it is an A/C heater supply, chances are you can abuse it enough to do it, maybe, maybe not.

At 3x the heater current demanded (didn't know that) chances are the manufacturer didn't provide enough supply to account for this. 

[EDS_]

Out of caution my buddy decided to ask his favorite equipment dealer about this.  That guy said NO!

[PaulFolbrecht]

These two tubes types are not even close to compatible, or even similar.

There are even circuits designed for the 5687 that can't run the 6900 due to current draw.  The 6900 is a heck of a little tube.