I was reading on the net that I can simply change out my 6L6 tubes for EL34 tubes without any problems. Is this true?
I would rather not name my amps brand name but it has 2 - 5881/6L6WGC power tubes. My guess would be to replace these with JJ EL34s then just rebias the amp.
Will this work as they say?
6L6 to El34 tube change
Moderators: pompeiisneaks, Colossal
Re: 6L6 to El34 tube change
There are three major factors that affect whether you can do this.
One if the PT's heater current capacity. 6L6 heaters draw 0.9A each whereas EL34 heaters draw 1.5A, so a pair of tubes will add an additional 1.2A to the heater supply requirement.
Two is the output tube socket wiring. 6L6 tubes don't use pin 1 so sometimes it's used for anchoring grid resistors or screen resistors to. EL34s need this pin grounded, so sparks can fly (or worse) if it has been used as a tie point rather than being grounded.
Three is the bias range available. The bias points are quite different so you might need to swap the bias range resistor if you can't get into the right range for EL34s.
Otherwise the output impedances are pretty similar so you don't have to worry about deliberately selecting a mismatch on your impedance selector or anything.
You need to check out items one and two first before trying this though. The manufacturer might be able to advise on whether the PT will support the current required for EL34s or you might have to try the old technique of firing it up, checking the filament voltage to make sure it doesn't sag down below 6.3V and then keeping a close watch on the temperature of the PT for an hour or so to see how hot it's getting compared to normal.
Not ideal or scientific but sometimes necessary in the absence of some hard-and-fast data.
One if the PT's heater current capacity. 6L6 heaters draw 0.9A each whereas EL34 heaters draw 1.5A, so a pair of tubes will add an additional 1.2A to the heater supply requirement.
Two is the output tube socket wiring. 6L6 tubes don't use pin 1 so sometimes it's used for anchoring grid resistors or screen resistors to. EL34s need this pin grounded, so sparks can fly (or worse) if it has been used as a tie point rather than being grounded.
Three is the bias range available. The bias points are quite different so you might need to swap the bias range resistor if you can't get into the right range for EL34s.
Otherwise the output impedances are pretty similar so you don't have to worry about deliberately selecting a mismatch on your impedance selector or anything.
You need to check out items one and two first before trying this though. The manufacturer might be able to advise on whether the PT will support the current required for EL34s or you might have to try the old technique of firing it up, checking the filament voltage to make sure it doesn't sag down below 6.3V and then keeping a close watch on the temperature of the PT for an hour or so to see how hot it's getting compared to normal.
Not ideal or scientific but sometimes necessary in the absence of some hard-and-fast data.
Re: 6L6 to El34 tube change
Thanks paulster for the help.
My amp is rated at 40 watts with the 2x6L6s, so what would it be with the 2xEL34s - do you think?
Again, thanks a lot for your help!!!!!
My amp is rated at 40 watts with the 2x6L6s, so what would it be with the 2xEL34s - do you think?
Again, thanks a lot for your help!!!!!
Re: 6L6 to El34 tube change
It's difficult to say because the plate voltage, primary impedance and the PI design (which may limit how hard it can push the output stage) all have a bearing.
It's likely to be very similar though.
It's likely to be very similar though.
Re: 6L6 to El34 tube change
Thank you Paul very much sir!!!!