The mark V:25 and rectoverb 25 both "suffer" from the same problem, and that is no master volume. The volume taper (even on 10w) is extremely aggressive and comes on fast. I picked up my rectoverb 25 head and 1x12 cab hoping for a low power option to my roadster and find that I get much better volume control and tone out of the roadster.
This really is something I agree with.
Amps were invented and designed to work in the context of bands; originally that meant big bands, later it meant rock bands. So by the 60s, amps got louder and louder. The tones we heard on records that became iconic were made with big amps, or with small amps cranked to the max to distort the power section of the amp.
The original reason for the rediscovery of low power amps 20 years ago, was the ability to crank the power tubes to the max without going deaf, to get a grinding old school sound as Page did with the Supro, or Clapton with a Tweed Champ. Great for studio work.
Only later did players get the notion that they could still get good tone from a lower power amp by adding a master volume, and calling it a bedroom amp. But run an old 12 or 15 watt Fender cranked, and you still have a very loud amp! Throw on a master, and yeah, it's not as loud, but there's not much tone left. That's the rub.
The whole point of a low power amp is to get the power tubes cooking! But with a master, most of them are dialed in to sound fizzy, and without the big transformers and so on that bigger amps have, the tone can go missing.
My HXDA 30 sounds different from my former HXDA 50, even though it has the same power tubes and transformer! What's missing is that low end, almost uncontrolled "the amp is about to bust loose" wallop that still comes through on the 50 even when the master is reducing the volume. That's almost as much a feel thing when you're playing as a tone thing. Hard to describe, but we've all experienced it I'm sure.
So I crank the master on the 30 to get close to that, and sure, it does sound close to the 50 at a slightly lower volume than the 50 if the 50's master is cranked. Only the 50 doesn't need to be as loud to get that wallop.
There's a trade-off.
And it is still a little different, not a smaller version of the same tone, because tube amps don't behave like a transistor modeling amp where turning down the volume sounds pretty much the same, just less loud (fletcher-Munson curve and speaker distortion notwithstanding).
There is one advantage to the 30 and that is I can involve the power tubes more in the studio at 3 db less volume, which matters to the mics and recording gear, but it's still plenty loud.
This is has happened with every MV small amp I've played through, regardless of brand. The lower the power, the less sense the Master seems to make.
My DG 30's master works best when the amp is switched to Boost mode. In its regular position, the master really needs to be at least 3/4 of the way up to get the best tone. Either way, though, it's loud. Also, it's very, very good sounding!
I guess my point is that the low power versions of most amps don't sound the same as the big amps regardless of master volumes, and the bigger amps' master volumes make more sense and wind up sounding better anyway.
For me, 2016 will hopefully mean a 50 watt, loud, DG50 and a 100 watt Archon if all goes well, to complete my amp Arsenal. Because I like the sound of bigger amps. Accept no substitutes!
