Hi,
The cap that Steve uses between pin 1 and pin 3 to enhance the sound on the 6p15p can cause problems in certain EL84's. I purchased a pair of Seimans EL84's from the 60's that were not compatible because the Seimens were internally wired between pins 1 and 3, where Steve placed  the cap modification. I know the 7189 will work, but 7189A has a slightly different pinout. My knowledge of tube's and tube circuits is very limited. If anyone has knowledge or experience  with the 7189A in the SE84 UFO I would appreciate any of your comments.
 
                                                       Thanks,
                                                              Bunky
                       

I use Telefunken 7189 in my Taboo and they sound great!  Not the 7189A.