EL34 Silicon Diode/Tube Recto setting

[JMPMAN]

Does it really matter if you use the silicon diode setting when using EL34's instead of 6L6's on the 3 ch DR? According to the back panel, it says that it's recommended to use the tube rectifier mode when using the 34's. Just curious.

 

[JMPMAN]

C'mon guys, I'm sure someone else has wondered about this :?

 

[stompboxfreak72]

Changing to silicon diodes will cause your tubes to run hotter. El34s are not as durable/reliable as 6l6s historically. From www.eurotubes.com :

"The Dual and Triple rectifiers are set very cold in the 6L6 mode even when in the solid state rectifier mode and the bold setting. So even the hottest 6L6's on the planet will still not get the bias as high as it could safely be run. When in the EL34 mode the bias is quite warm with even a moderate grade of EL34's which is why Mesa will tell you that if you're going to use EL34's that you have to run them in the tube rectifier mode. The reason for this is because when the stock 5U4 rectifiers are switched in the plate voltage drops from about 475 on average to about 415 volts so in turn the bias goes down."

My experience with this has been that I do not get much life out of el34 in my DR. The irony is that I also have a Single Rectifier which has no 5u4 tubes so is therefore always in silicon diode mode. It can be run with el34s. Always baffles me. Perhaps it is biased so that the tubes are not getting pushed as hard. Jury still out on that one.......

 

[JMPMAN]

Thanks for a very thorough explanation 8)