The mid knob...not as much. It doesn't seem to have as much effect as I was expecting.
That's not really unusual for a mid control on some amp designs, especially Fender type tone stacks where the midrange control is very much dependent on the position of other controls on the amp, especially the bass and treble controls. Even traditional Marshall midrange controls can be quite subtle, depending on the other controls' positions.
To my way of thinking, the midrange is where guitar tone lives, and there's probably a trade off of some kind between a really good, creamy midrange tone, and a mid control's range.
Example: on lots of old Fender amps, the mid control works most like a mid control when the bass and treble are dimed. Otherwise it seems to affect gain or punch more than act like an EQ. The Mesa Blue Angel had a similar kind of control and even addressed this in the manual (it really acted like a gain control in the second half of its range).
On my DG30, the mid knob does most of its work between "off" and "noon" (the cut side) with anything over "noon" on the boost side being very subtle at best. If I turn the bass and treble controls to "0" I can hear what part of the frequency band it's working in, and at about noon it becomes a very subtle control indeed, though I do hear a small difference between noon and dimed.
On the other hand, when I crank the treble and bass, it's a little different, especially with the lower mids. Since I don't generally dime the bass and treble, I use it as a mid-cut, to tame overly bright guitars, pedals, or speaker cabs. Often the "ice pick highs" some folks make reference to are located more in the mids unless you're right on axis of the speaker cone.
As with any amp, there are design trade-offs; make one control do more, and you have to make another control do less, or alter the tone of the amp in a way you don't want to.
In any case, try experimenting with the other tone controls off, just to hear what the mid control does in a vacuum, and then try it with the bass and treble cranked, and see how it can possibly change.
If you find you need more mids but you're otherwise happy with the amp, you might want to experiment with a Fulltone Secret Freq, or a Suhr Koko Boost, both of which have variable midrange boosts and sound very good indeed!
