Using all EL34's in. mk III

Hi guys, new to the forum but been using a purple stripe MK III among others since '87. I've always thought this amp had a tendency to sound a little dry especially on crunch and lead and I've tried running on class A and it seems better,tried Class A with 6L6 , not so good. Just tried using all EL34's and bingo! It sounds great! Now,these amps were marketed originally as having interchangeable valves, but on contacting Boogies importers here in the UK, they tell me no as the plate voltage is different and obviously they are hard biased for the 6L6's. Has anyone else done this? If so with what results?
I also have a V-twin which sounds amazing when fed out via the "power amp output" into the f/X return on the mark III, beautifully creamy and lush. This bypasses the pre amp on the Mk III but not the graphic, again anyone tried this or with another host amp?
I've also had a little mod done (boogie authorised) where I have a trim pot over the rhythm 2 valve which alters the gain on R2. So I'm guessing it's not all purple stripe anymore! Very neat

Chalkythecat said:

Hi guys, new to the forum but been using a purple stripe MK III among others since '87. I've always thought this amp had a tendency to sound a little dry especially on crunch and lead and I've tried running on class A and it seems better,tried Class A with 6L6 , not so good. Just tried using all EL34's and bingo! It sounds great! Now,these amps were marketed originally as having interchangeable valves, but on contacting Boogies importers here in the UK, they tell me no as the plate voltage is different and obviously they are hard biased for the 6L6's. Has anyone else done this? If so with what results?

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You can use EL34's in the outer sockets of any Mark series Simul-Class amp including your MkIII

I know that, I'm asking if anyone has tried them in all the sockets including the 6L6 sockets and if so how did they find it?

I have a comment/question on a similar subject that I have been wondering about for a while. Why did Mesa use el34's for the class A section of their simulclass amps? If el34's sound better for recording with straight class A then why would they then make a lower watt version with 2 6L6 tubes?

There is a 60 watt (2 - 6L6) 2c+ for sale in my local area and I am flirting with the idea of buying it but I have done enough testing with tubes to know that I like el34's best so if I were to pick this up I might want to modify it and have the only straight el34 2c+ that I have ever heard of.

Has this ever been done? Would it even be possible with the existing circuit board?

Chalkythecat said:

I know that, I'm asking if anyone has tried them in all the sockets including the 6L6 sockets and if so how did they find it?

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Those sockets were not designed for EL34's so it's not advisable.
EL34's can't handle the voltages of the 6L6 sockets.

Rob227 said:

I have a comment/question on a similar subject that I have been wondering about for a while. Why did Mesa use el34's for the class A section of their simulclass amps? If el34's sound better for recording with straight class A then why would they then make a lower watt version with 2 6L6 tubes?

There is a 60 watt (2 - 6L6) 2c+ for sale in my local area and I am flirting with the idea of buying it but I have done enough testing with tubes to know that I like el34's best so if I were to pick this up I might want to modify it and have the only straight el34 2c+ that I have ever heard of.

Has this ever been done? Would it even be possible with the existing circuit board?

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No, and why bother.
If you want a vintage straight EL34 amp go buy a Marshall

The amp doesn't have a GEQ so if I were to send it in to Mesa to have one added I could also request any other mods at that time. Otherwise you're probably right, why bother.

It might be cool to have a unique amp if it were done.

Rob227 said:

The amp doesn't have a GEQ so if I were to send it in to Mesa to have one added.

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Well the EQ faceplates are long gone so it is not possible unless you have a faceplate already.