Out of the box experience, Roadster, MWDR are not all that compatible with the 7 string guitars. Perhaps I am doing something completely wrong. I still refuse to run an OD up front so the only other option was to find out what preamp tubes I have on hand that works. Sorry about the talk about the glass here. No need to turn this into a tube discussion. I did not want to say, yeah, Roadster is awesome with the 7 string without some supporting information how to get there with it.
KT77, interesting. Not sure how that would work in the Roadster. Not sure how the Roadster compares to the Road king, that amp has a few more tricks to it. Same preamp but different power section.
If you want to run a "Dad Rock" I would also consider the Badlander. We play mostly classic rock form the 60-70's At least that is when most of the music we play came out. Some 80's too. I go for more of a modern thing but the BAD is a surprising amp right out of the box. Fully 7 string compatible too. I would not make that the deciding factor unless that was your goal.
The BAD is similar but different from the Mark IV. One would think it is much the same as the Mark VII, that circuit is in that amp but still different so having the BAD and the Mark VII is not a redundant thing. I generally look past the death metal sound and want more than djent or grunge. Sure, I can get into that heavy tone too or style, but would prefer more versatility.
Probably why the Roadster is a keeper, The gain modes on the two clean channels are good. So are the medium gain raw and vintage. I still prefer the modern mode so that is what I run with the Roadster or MWDR. My other amps cannot do that. Even going soft with the tube tracking and spongy mode has its value. Actually that is one way to get the Roaster or MWDR from fighting you with the harmonics. The Badlander cannot touch the Roaster or MWDR spongy mode with tube tracking, it does not have rectifier tubes, only variac power. Aslo does not have the cold clipper circuit so it does not give you those low sub-harmonic tones. That is sort of what is cool about the Dual Rectifiers.
Shortly after getting the Badlander I started looking into what could be done with the other two amps.
Since I have the tubes on hand, why not try them.
Loaded the full preamp up with them. A few were NOS Ruby versions. Not easy to find these days.
Then the STR440 tubes are now out of production. The STR440 Reds just worked the best. Now the Roadster is a 7 string compliant amp. That was unexpected as it was not the intended goal but did have the one 7 string out to give it a go. That seems to be the thing I end up doing when I get a new amp. Run every axe into it and see if I can make use of it.
Those old Mesa tubes also work well in the Mark IVB. Back in the day, they were the only 12AX7 tubes you could find in the Mesa box (1989 - 1992). Not sure when Mesa brought in the JJ ECC83S but my Mark IVB was loaded with those. Bought it in 2000. I held onto the preamp tubes from the Mark III as I changed all the tubes in the amp every 3 to 5 months usually after red plating the EL34 pair. It was a DRG.
It is not the end of the world if you cannot find those preamp tubes. The Roadster sounds great with the stockers. However, not so good with the 7 string as it will flub out on you, just not tight enough.
Now comes the issue with the Power tubes. STR440 no longer available. Tried the STR445 in yellow, seemed to be too much tube for the amp. There are other tubes, Tung Sol 7581A sounded good. Have not run those with the Chinese military tubes though. Roadster needs a power tube with plenty of headroom or it will just sound off (like it is not biased correctly). Some may favor the SED =C= 6L6GC in the Roadster. Getting used to the change in character of the amp with alternate tubes is probably where I struggle.
We all have our opinions on tubes and such. Not trying to influence you one way or the other. I personally like the Roadster for what it is. Just as much as I like the MWDR and the other amp I have. Just figuring out how to make the best use of it that may be different from its image or target user. I do not care if it chugs, I know it will, just how does it perform when I want to use it for something else? I would not pigeonhole the Roadster into one class. It can do well with different music styles. Some amps may be more suited for that but there is a lot of amp packed into that box.