Mark III Simul Class question

[mincy]

I have a Mark III red stripe. It says simul class on the back and has a full/half power switch on the front. In the manual, it says to run el34s and 6l6s, you need to flip the Class A or 60/100 switch. Is that the same as the full/half power switch? I've never run it with El34s and I think I'm overdue, but I want to make sure I don't screw it up.

 

[edward]

With the 1/2 power switch on the front panel, may I guess that you have a long head? If it says "SimulClass" on the back, then you have a simul amp; thus designed for 6L6 in the middle pair, EL34 as the outer pair. So if you've been running four 6L6s all this time, you can't "screw things up" by replacing the outer pair with ELs since the amp was designed for just that.

The 1/2 power switch on the front is confusing. Mesa put this switch on the front of the long heads, whereas on the short heads and combos the switch was (correctly labeled ) "Class A/SimulClass," and located at the rear of the chassis. Your switch accomplishes the same thing. And when you drop into "Class A" you are not cutting power in half; you are taking it from the 75watts of Simul power down to 15watts of EL34 power (i.e. just the outer pair of tubes). Now if your outer pair is still 6L6, then your so-called "1/2 power" is probably in the neighborhood of 25 watts via 6L6s wired in triode. Hope that makes sense.

Edward

 

[mincy]

With the 1/2 power switch on the front panel, may I guess that you have a long head? If it says "SimulClass" on the back, then you have a simul amp; thus designed for 6L6 in the middle pair, EL34 as the outer pair. So if you've been running four 6L6s all this time, you can't "screw things up" by replacing the outer pair with ELs since the amp was designed for just that.

The 1/2 power switch on the front is confusing. Mesa put this switch on the front of the long heads, whereas on the short heads and combos the switch was (correctly labeled ) "Class A/SimulClass," and located at the rear of the chassis. Your switch accomplishes the same thing. And when you drop into "Class A" you are not cutting power in half; you are taking it from the 75watts of Simul power down to 15watts of EL34 power (i.e. just the outer pair of tubes). Now if your outer pair is still 6L6, then your so-called "1/2 power" is probably in the neighborhood of 25 watts via 6L6s wired in triode. Hope that makes sense.

Edward

That was kind of what I thought, but seeing as the manual specifically says Class A and 60/100, not full/half, I wanted a 2nd opinion before I gave it a shot. And yes, it is a long head, so what you pointed out fits. Thanks.