Can I use EL34s with my Blue Stripe?

I recently acquired a spotless wide-body Blue stripe Mark III. It does not have a simul-class switch or reverb and is currently loaded with a quad of 6L6's. My belief was that EL34s on the outer sockets was reserved for the simul-class versions but someone has a similar blue stripe for sale in the classifieds with the 6L6/EL34 combo.

My favorite tube is an EL34 and I would like to hear this combination so any info would be appreciated!

My belief was that EL34s on the outer sockets was reserved for the simul-class versions but someone has a similar blue stripe for sale in the classifieds with the 6L6/EL34 combo.

Click to expand...

Correct. You can only safely use all EL34s or a combo with 6L6s in a 100W if you mod the amp and play with the bias. This is not recommended.

The one for sale with the 6L6/EL34 if it's non simul has either been modded or the guy is an idiot and should pull those EL34s out as soon as possible before they blow something up. Stick with quad 6L6GCs.

Thank you. If the mod is done does that essentially give me a "simul-class" or is it still non-simul-class that can now handle EL34's?

Pretty much all the clips I've heard are of simul-class versions and now I have a non-simul-class. Since I'm comparing clip to personal use I can't really get a handle on what the tonal differences are.

Hmm actually I think you can only mod to ALL 6l6GCs or ALL EL34s. Sorry to be misleading. The 'mod' is changing the bias to use EL34s whereas the simul class being able to use EL34s on the outer sockets has a different wiring, bias, power setup and transformer. I'd recommend against it as you're stuck with one or the other unless you mod it again. It's all to do with the bias being fixed on boogies.

I'm not sure if you can do it without using a simul class transformer. I've never tried it. I'm pretty sure you need a simul transformer. There's a reason why boogie would use a different transformer in each.

If it's a simul class sound your after, sell/swap it and buy a simul class amp. It'd be far more cost efficient than sourcing a simul transformer and swapping that. If you like your tone then stick with it...

Personally I really like the 100W Mark IIIs. The tonal difference is very little in 'Class A' mode on the simul class. When simul is enabled it blends class A and class AB together to create a richer sound.

The simuls themselves also have different component values and are a bit brighter in the preamp and lead sections to compensate for this. Same essential sound though really. I'm some people will disagree with this though.

I think I’ll hang onto this big boy. Sounds good and looks practically new. I also have a purple stripe combo. I think down the road I’ll shoot for a 3rd, either a red stripe or early model with the 105 PT. I’m new to the Mark iii game. Kind of addicting.

lgehrig4 said:

I recently acquired a spotless wide-body Blue stripe Mark III. It does not have a simul-class switch or reverb and is currently loaded with a quad of 6L6's. My belief was that EL34s on the outer sockets was reserved for the simul-class versions but someone has a similar blue stripe for sale in the classifieds with the 6L6/EL34 combo.

My favorite tube is an EL34 and I would like to hear this combination so any info would be appreciated!

Click to expand...

Some Long Heads/ Widebodies were not labeled as Simul-Class even though they were. They had a "1/2 power" switch but the switch was really for switching between Class-A and Simul-Class.
The only way to tell is to pull the chassis and see what Output transformer is in it.
If it's a Simul OT then you can use EL34's in the outer two sockets

gts said:

lgehrig4 said:

I recently acquired a spotless wide-body Blue stripe Mark III. It does not have a simul-class switch or reverb and is currently loaded with a quad of 6L6's. My belief was that EL34s on the outer sockets was reserved for the simul-class versions but someone has a similar blue stripe for sale in the classifieds with the 6L6/EL34 combo.

My favorite tube is an EL34 and I would like to hear this combination so any info would be appreciated!

Click to expand...

Some Long Heads/ Widebodies were not labeled as Simul-Class even though they were. They had a "1/2 power" switch but the switch was really for switching between Class-A and Simul-Class.
The only way to tell is to pull the chassis and see what Output transformer is in it.
If it's a Simul OT then you can use EL34's in the outer two sockets

Click to expand...

Interesting. Mine has a half power switch on front so I’ll have to take a peak inside. What am I looking for in regards to the transformer?

lgehrig4 said:

gts said:

lgehrig4 said:

I recently acquired a spotless wide-body Blue stripe Mark III. It does not have a simul-class switch or reverb and is currently loaded with a quad of 6L6's. My belief was that EL34s on the outer sockets was reserved for the simul-class versions but someone has a similar blue stripe for sale in the classifieds with the 6L6/EL34 combo.

My favorite tube is an EL34 and I would like to hear this combination so any info would be appreciated!

Click to expand...

Some Long Heads/ Widebodies were not labeled as Simul-Class even though they were. They had a "1/2 power" switch but the switch was really for switching between Class-A and Simul-Class.
The only way to tell is to pull the chassis and see what Output transformer is in it.
If it's a Simul OT then you can use EL34's in the outer two sockets

Click to expand...

Interesting. Mine has a half power switch on front so I’ll have to take a peak inside. What am I looking for in regards to the transformer?

Click to expand...

It'll have Simul-Class embossed in the metal on the OT.
It'll also have either SC152019B or 562003, probably 562003 due to it being a Blue Stripe