Tweaking Tip/Idea - Mesa Mark Series Amps & Running 2 EL34'S In The Outer Sockets

shredi knight

shredi knight

Power User
I've always heard how with Mesa Boogie amps with Simul-Class, that they are able to run using both 6L6 & EL34 power tubes at the same time and many users prefer them this way (John Petrucci has been known to have his Mark series heads loaded with two 6L6's in the inner sockets, and two EL34 'S in the outer sockets). Since with 10.00, we now have the ability to choose the power tube type in the amp block, Tetrode (6L6, KT66, etc.) or Pentode (EL34, 6BQ5, etc.), I had the idea of maybe being able to simulate this by running two of the USA Lead amp sims in the same patch, but with one of them set to Pentode (EL34) instead of Tetrode (6L6).

I just started playing around with this this morning, but I am liking the results. Definitely worth trying for adding a little different flavor to the usual Mark series 6L6 type tone. You can use any combination of the USA Lead sims, but you are likely to get nasty phase cancellation (I do at least) unless you have them panned hard left & right. You can blend two of the exact same amp sims together without any phase issues though, unless maybe the settings greatly differ between the two (so far I have only experimented with using 2 of the same amp sim with the same settings, so I'm not sure about that).

Anyway, just an idea I had that I thought I'd share. Obviously you can so this with any of the Axe's amp sims, but I am using the Mesa Mark amp sims as an example since using different power tube types can be done with their real world counter parts.
 
Just FYI for anyone interested. The Simulclass power setup of the early Mark series did indeed use a pair of 6L6s and a pair of EL34s. The biggest thing that gave them the sound they had was that one pair of power tubes were biased to operate in Class A the other pair was biased to operate in Class AB. Generally I believe in the older Mark series the EL34s were biased in Class A. When the quality of EL34s became too unreliable the changed to all 6L6s, one pair Class A one pair Class AB.
I am pretty sure its not possible to do this in the Axefx. Maybe Cliff will chime in on weather he actually modeled SimulClass or not.

I am not taking away anything from your experiment, because if you're digging the sound and its working for you go with it!
 
groovenut said:
Just FYI for anyone interested. The Simulclass power setup of the early Mark series did indeed use a pair of 6L6s and a pair of EL34s. The biggest thing that gave them the sound they had was that one pair of power tubes were biased to operate in Class A the other pair was biased to operate in Class AB. Generally I believe in the older Mark series the EL34s were biased in Class A....
Click to expand...

Then wouldn't turning the "Pwr Tube Byass" parameter all the way up put the amp sim that is set to "Pentode" (EL34) simulate the amp running in Class A?



From the Axe-Fx II manual:

"Power Tube Bias - Sets the bias point of the virtual power amp. Lower values approach pure Class-B operation. Higher values approach pure Class-A operation."
 
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Hmm it would seem so (referring to the bias adjustment).
Is there anyway to bypass the preamp so that you dont get the filtering effects of all the RCs at each gain stage? If you can that would get you closer. There's still the issue of bypassing the phase inverter stage. One other issue arises as Randall Smith claims that one pair is in Class A, they really arent in true Class A. So you may have to experiment with AxeFx values close to but not quite pure Class A.

Unless Cliff has already modeled the SimulClass power stage, your experiment is probably the closest you can get.
 
Yeah, it's just an experiment to see what it would sound like. It's probably going to end up being one of those things that when you first try it, you say, "Holy shitballs, that sounds great! I'm redoing all my patches this way!", but after awhile you prefer the way you had it with just one amp sim running. Time will tell. I really don't even know what I'm aiming for since I've never played a Mesa with Simul-Class and don't know what the tonal difference are between that and a Mark with all 6L6's. I do know that I did not like the way it sounded with the bias turned up on the one amp sim. I've always liked the sound of running the bias low on the Mesa amps (around 0.200). Up high and it sounds too round and bland for my tastes.
 
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In my Mark III Simul-Class, I had it shipped from Randall Smith with all 6L6s, but also had them include a few EL34s to experiment. This was in 1986!

Running the amp in full power had both pairs on (inner pair and outer pair). Switching to half power from what I understand effectively had the amp in pure Class A power! This cut the power from 75watts (give or take) to roughly 15 watts or so! But dang....that 15 watts was LOUD and JUICY!

Randal Smith found a way to "couple" the 2 power amp circuitry together yielding more power but with the Class A imparting it's smooth "vocal-like" quality over the overall sound!

I preferred the 6L6s over the EL34s in the outside sockets. I liked the power chord gain sounds and presence of the EL34s and the "looser feel" put it was too "harsh" in the solo side and I preferred my solo tones taking precedence overall. Incredible sounding amp!

I definitely look forward to trying out your suggestions as I could have the best of both scenarios!

I must admit, those Mark series simul-class amps imparted a certain "magical" dimensional sound! I still have it btw, all hardwood 22" head and a 2x12 cab!

Thanks for bringing this up Shredi!
 
If you really wanted to shoot for this kind of sound, you could put two amp blocks on the grid in parallel, then set both types to the same Mark amp, then set the rest of the amp's parameters to be exactly the same, but set one for the 6L6 tube type with normal bias and the other for EL34 tube type with a bias of 1.00. Adjust the volume of each to taste.
 
if you get something you like plese share
I used to own a Mark Iv and and a Mark III(red stripe) and I always ran with in Simul class with El-34's on th eoutside.
Actually with my III I ran KT-77's on the outside, that combo kicked major butt, and I have not been able to reproduce with the Axe II as of yet.
I actually have a patch that I blend the HBE and the Plexi together and it gets me a very accurate representation
of a JSX on it's crunch channel (I jsut sold one so I tone matched by ear
as best as I could) so this type of blending should yield a positive result.
 
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