hey guys, this is a follow up thread to my last one...


i just called a tech a few minutes asking him about changing my el34 poweramp to 6l6s,

he said if i could find some laid out instructions on how to do it, he'd do it for me

however i cant seem to find any info on how this is done.

please help me find some reliable info on making the switch from el34s to 6l6

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Why do you want to do this? Do you play at stupid high volumes and want old fashioned rock powertube saturated sounds? If not, keep the 6l6s in your poweramp or sell it and get an el34 poweramp. Or possibly contact a different technician that knows what he's doing. I wouldn't take my amp to some dude that requires me to fetch him instructions how to bias my amp right, it just reeks of inexperience to me.

Not worth the effort, risk or money IMO.

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lol

no, you see my poweramp CURRENTLY has el34s and i want to switch these 34s to 6l6s

its a pretty sweet ENGL 920 poweramp btw

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shouldn't it technically require... new sockets, new bias pots (for different current draw) and possibly a new transformer...

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It will not need new sockets and the OT should be fine, but the bias will need to be adjusted. There are several ways to have this done. For a good tech it would be no problem. Find a new guy to work on your amp.

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oh LOL my bad I read it the wrong way. Guess my love for 6l6s fueled that post. Yeah like soulinsane said, find a tech that feels more comfortable doing it.

Your tech might not know how to do it on your amp bc its an Engl though, I'm guessing most techs in North America don't have much first hand experience with Engls.

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I agree with Soul on this. If the tech needs to have the instructions laid out for him, then he doesn't know what he's doing, and shouldn't be working on your amp.

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haha, i live in a small place, i really dont think i can find a better tech around, might just have to buy El34s again

soulinsane do you have any more info on the bias adjustment for me?

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I could give you a million different sites actually.

I personally like using a fixed bias method but I think it should be called an adjustable fixed bias method. Its easy and fast to adjust bias for even mixed pairs of power tubes if each tube has a variable resistor on the grid pin, in fact you don't even have to use matched pairs if done correctly. A 1 Ohm resistor is placed between cathode and ground. This allows measuring the voltage across that resistor to determine the current in the tube. With a 1 Ohm resistor, 1 mV=1 mA in the tube. By adjusting the grid voltage ( FYI, which is a negative voltage on pin 3 if I remember correctly ) the amount of idle current through the tube is also adjusted as read on the 1 Ohm cathode resistor. If the amp has a fixed resistor on the grid I like to replace them with a variable resistor to make adjustment easier and more precise in the future.

That's is in a nut shell, but take a little time and learn about how plate voltage affects tube replacement and the simple math involved by searching and reading online. Everything you need to know is there if you put the time into it. It will allow you to fine tune your tone and use just about any tube or mixed pairs of tubes that you want. I'm using 2 pairs of Sovtek KT88 and GT 6L6B tubes in my Randall RM100 ( which comes stock with the adjustable bias modification that uses the fixed bias method ), A/Bed with my solid state Randall Cyclone for crisp sizzle into a stereo 4x12 cab.

The coolest but also most expensive bias method I have seen involved using servos that constantly adjusted the grid voltage on each tube to maintain perfect tube balance and bias in real time over the life of a tube. Basically, from the time you install a new tube until it dies or is replaced, the amp will adjust itself to maintain the bias you determine. A similar and cheaper method uses differential op-amps to adjust grid voltage but servos are just fucking cool

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