7189 tubes in aLead & Bass 20?

Chi

Silver Supporting Member
Messages
994
Howdy guys-
I've got a 73 Lead & Bass 20 that sounds great. Brought it to rehearsal the other day and it smoked. I had it dimed, but our drummer hits kinda hard.

I just scored some 7189 tubes (they are in the same family as EL 84's) and wanted to know if it was safe to put them in the LB 20... I'm pretty sure I can put them in there as the Plate voltage on the LD 20 is pretty high...

Just to make sure, is it OK? Also, generally speaking, what will the 7189 do to the sound besides make it a bit louder?

Are there any guidelines for situations where I SHOULD NOT use a 7189 instead of a EL84?

Any feedback (no pun intended) would be great.
 

Swarty

Member
Messages
1,131
I have a couple of Marshall 20s and run 7189s in them because they are tough on tubes. The 7189 is rated for 400V where an EL84 is 300V. Louder, better bass, clearer top...stiffer/tougher feel... Similar to putting 6550s in a 6L6 circuit.
 

Kiwi

Silver Supporting Member
Messages
4,081
Yes, the 7189s are actually a good idea. The L&B 20 runs very high plate voltages and the 7189s should be able to handle them better than modern-day EL84s.

Kiwi
 

Jeff West

Member
Messages
1,060
Remember though that although 7189 has same pinout as EL84, with no internal connections on pins 1 or 6, 7189A which is commonly encountered and has higher screen rating than 7189 actually does not have identical pinout: on it, pins 1 and 2 are internally connected (and to control grid), as are pins 6 and 9 (to screen grid). There are some applications where 7189A can't simply sub for 6BQ5/EL84.
 




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