NAD Mark III long head blue stripe

[woodbutcher65]

Kind of unexpected, but I landed a deal on a Mark III long head blue stripe loaded head today at the Orlando Guitar Show.

Plugged into my Marshall cabinet, it's positively brutal in all the right ways. Everything works as it should, and apparently R2 has already been modded, since there's no level jump.

But I have questions. I'm no stranger to Mesa, but I don't know this one.

As is typical of Mark IIs and IIIs, it has one 8 ohm and two 4 ohm speaker jacks.

My Marshall cabs, both of them, are 16 ohm. And they're single jack cabinets so there's no parallelling them at the cabinets.

Do they present an unsafe load to the Mark III?

To run both cabs I'd have to plug two 16 ohm cabinets into two 4 ohm jacks. That should give an 8 ohm load. I THINK that'd be OK but I'd like confirmation of that.

The short term plan is to rewire certain cabinets to present 4 or 8 ohm loads. I have four 4x12s, enough to go around for sure.

 

[GJgo]

It's a safe mismatch. Also, if your new head is a HRG, and you flip it to 60W mode, then it's actually a correct match.

I used to have a Marshall 1960 cab, I just re-wired it to a pair of 8 ohm jacks ("dual mono") then using two leads it was a correct match.

 

[woodbutcher65]

I haven't pulled the chassis out of the cabinet yet to see if it's a 60/100 or a simulclass. It has a half power switch on the front row.

Currently it's equipped with a quad of STR 440s.

I'm betting it still has original filter caps. I'll be replacing those very shortly if that's the case. I should have a set in stock.

 

[woodbutcher65]

Yeah, the main caps are dated 8808. The amp is as pristine and clean as I've ever seen. Quite a jewel. One smaller electrolytic capacitor in the power supply section MAY have been replaced at one point but I'm not sure.

Oddly, it's not marked HRGX or DRG or anything on the sides of the chassis.

Looks like a straight 60/100 model. No resistor differences on the tube sockets.

 

[GJgo]

Cool.

Mark IIIs have so much hair I think they work better with G12T75s than they do with V30s.

 

[woodbutcher65]

Honestly I've never warmed up to V30s. My cabs have Greenbacks or G12T75s. I also like EVs but that's a totally different world of tones.


Got a reverb related question for this Mark III. Are they supposed to run 12AX7 tubes in the reverb circuit, or are they designed for a 12AT7 driver tube? This one has a pretty low level reverb.

 

[GJgo]

12AX7. Mark III reverb is super weak. Even after Mike does his reverb mod it's still kind of weak. Best thing you can do is get a reverb pedal.

 

[xdg999]

Congrats on the new amp! I picked up a Mark III SRG head last week in mint condition. It rips! It's on it's way to Mesa for the III+\R2 mods and general service. The chassis has the hole for the fan outlet so I'm also getting a fan installed in the headshell.

 

[woodbutcher65]

Speaking of fans....I found that the inside parts of the internal slim profile AC jack for the fan, next to the transformer, are MISSING. If I unplug the fan I can simply pull the AC power jack body clean out of the chassis with no effort, leaving two live contacts just hanging in the chassis and possibly shorting to it. Why the internal parts of the jack are gone, I have no idea. It's not even impossible that those parts may have not even been installed at the factory. I've contacted Mesa for replacements.