Reverse Diode protection for Power Tubes?

[leadfootdriver]

I seen it on a Trainwreck layout. I wanna' put it on my single EL84 amp.

The Wreck has 3 diodes grounded from the plates on each EL34. How did he come up with 3 for each tube?

[Jazz P Bass]

The three diodes in series are probably 1N400- something diodes.
Running them in series increases there voltage handling ability.
Read this link:http://music-electronics-forum.com/t14732/