That's very timely that you replied to this in regards to the DC-30 because I just put up a new post in the Axe iii forum about this amp and how I struggle with it haha
Also, I know "muddy" can sound negative, so I hope you don't think I'm poo pooing on that creamback pack. I've used it for many things, but it just seems like for the AC-20, it doesn't pair well without either getting peaky, or just blankety sounding, which I assume not all amps are a good pair for every cab. I can try some single captures though and see. I'm also not married to the AC-20 either, especially now that gapless switching has been implemented; it just seems like one of the only Class A amps that can actually handle an array of tones from clean to tight modern high gain.
That being said, I'm very curious about what kind of guitar and pickups you're using with the DC-30 and what kind of tones you are going for? Also, leaving the master on 10 for me always results in the tone becoming like a bit crusher, but maybe I'm trying to make the amp into something it was never intended for. At the time when gapless switching didn't exist, I was looking for a pedal platform amp that could do everything from clean to edge of breakup to crunch to even tight modern high gain, and that one (the AC-20 Treble) seemed to take all pedals the best, whereas the DC-30 seems mega picky, so that's why I'm surprised when I hear people say that the D-30 is a great pedal platform because I just find it to completely fall apart, so I'm wondering what I'm missing or doing wrong.
It's interesting too; you mention the Matchless (DC-30 I assume?) to sound great with the Mesa OS on mix 1, and I immediately think "How???" hahah not denying it does because I know if I heard the tone you were getting with it, I would go "HOW??????" hahahahha That being said, how are you dialing that amp in? Are you adjusting the impedance curve to that as well? What type of tone are you going for and what guitar/pickups etc.? Perhaps I'm just trying to make the DC-30 do something it was never intended for, so I'd love to hear more about this. I know the DC-30 was big with Praise and Worship tones too and they tend to stack drives, so I'm wondering how that's feasible without things turning into a bit crusher or bottoming out when on the neck pickup. I find it difficult to get great chime and attack with that amp. It generally sounds and feels stiff, dry, and murky/loose in the low end. The only thing I've found that helped was by turning the master down, which is why I'm surprised to hear how many people leave the master on 10. I'm just ranting now haha but since you know the amp well, I'd love to hear about these tones you're getting and for what style, and more insight on what the DC-30 can and can't do.