McCormack Advanced Rectifer Circuitry

Can you provide any more info about this? Now's the first I've heard of it, and the SMc website's link for it is inactive at this time. (Same for the DNA-500 mods -- the link placeholder's been there for a while, but is still not active.)

I am also curious about the ARC upgrades, but for the DNA-0.5 or DNA-1.0.

Here are the details I received in an email from Kris at SMCaudio about upgrading a DNA-0.5. Not sure if the ARC-1 and ARC-2 are included in the price of the DNA-125 Platinum upgrade.

The ARC-2 replaces the original IXYS soft recovery diode option on the outputs. Cost is $500.00 and is available on all McCormack amps except the HT-1 & HT-3.

The ARC-1 is a variation of the ARC-2, but is installed on the main AC power supply. Cost is $285 and is available only on the DNA-125 and DNA-225.

Howard,
When yours is scheduled?
My DNA-125 at SMC shop right now for a Platinum + ARC2.
I'll let you know when I get it back (4-5 weeks).
BTW, I've heard DNA-225 with ARC2. Although it still has less than 100 hours brake-in time, it's really something, but I'll let the owner of DNA-225 speak for his amp.

Howard,
It's hard for me to tell what impact the ARC2 mod had on the performance of my amp, since I had everything done at the same time. I had it scheduled for Gold originally, but while the amp was there I figured I'd do couple more things. I talked to Kris and Steve about getting a Plitron, but Steve suggested that I try the ARC2 instead, since the DNA-225 already has enough power to drive my(or pretty much any) set of speakers.
Although the amp is not fully broken in yet(less than 100 hours playing time), as Nyran94 noted above, it is sounding very good. Way better than stock. And it seems to get better as it plays more, so.....
I wish I could be more helpful with opinions just about the ARC upgrade, but, don't know.

You tell us when you get it back!!! :)