the Mc50 is the smallest of that series. They never had Power Guard, none of them. They all had "Sentry Monitor" limiters which was our theoretical limiter that we heard in Jerry's tone. But recently Dan said Jerry's 2300 did NOT have the limiter, likely referring to the Sentry Monitor since its the only limiter that ever could have been there. From what we can gather so far, it would have had to have been removed by DH as Mac has no evidence that they ever released an amp from that series without it. So the theory has now morphed into the idea that Jerry's power amp clipping was pure transistor clipping, and not the previously speculated combination of clipping and Sentry Monitor limiting.
So the Mc50 is the smallest in the series. 18 lbs. and tiny. Very portable. And about as loud as a Twin Reverb since it actually peaks at about 75 watts. It's half the Mc250. The Mc2100 is a stereo 100wpc version. I think there is a Mc100 out there too, a mono half of the Mc2100. Lately Stu Allen has been using his Mc250, each half driving its own JBL K120. If one side of the amp fails, he's still got the other half going. I like that insurance.
Stu and I experimented with the Sentry Monitor limiter in place and removed, and we both agreed that at least with the Mc250, that the removed limiter sound was better. The distortion that resulted was cleaner and purer, less fizzy and complex. The Sentry Monitor limiter kicks in as the amp reaches distortion, and imparts a bunch of its own distortion as well on top of the transistor clipping. The sound with the SM limiter is weirder and messier sounding. The removed SM, so far in our testing, seems quite spot on JG. It does make the amp a bit more vulnerable due to the lack of peak-current protection, but if a player is careful and doesn't drive the amp WAY past its limits, I think it should hold up nicely. Only testing on a loud stage with real band volumes will tell how they handle the misuse. The theory still holds that much of Garcia's Mcintosh magic comes from the abuse and misuse of the power amplifier, driving it to and past its inherent power limits.
... and it's just like any other day that's ever been...