My issue with communication is TMI. I get a notice from my boss many times to be more to the point and leave out the weeds.
The only battle I have with the Mark V is the high frequency response. Not enough roll off in the upper registers and tends to get brittle at times. I like to feel my music as well as hear it. I typically use the Mark IV mode due to the compressed tone. My favorite mode however resides in CH2 crunch which lends itself to a punk heavy metal tone with the gain dialed up to about 2 o'clock, mids about the same, bass at 12 and the treble dialed down to 10 o'clock (raise for lower for different attack) Presence can be used to tune the chug so I keep it low. The EQ set to preset with control knob at noon.
Extreme mode, that is a favorite too. All depends on what guitar I am using and what tone I am after. Works great for Billy Squire "lonely is the night intro" or the entire song. For Scorpion tones I use Mark IV or crunch. Same for Led Zep. CH2 Crucnh for ACDC sound. What I like the best overall out of all three amps, hands down the Mark V clean channel is the best for what I do. Piano like tones in the clean channel setting is amazing. 30 years means nothing (8 years of no guitar playing due to injury, now relearning how to play again).
In honesty, I like the oversized cabinet. Having a proper marriage of drivers to the size of the cabinet matters. EV is a good speaker after they break in. They are super tight during the break in process (recently replaced two that were bought used with new ones, now tone is tight and bright and will be for at least 2 more months) I prefer the Zakk Wylde black labels for the low end response. Classics have a softer bottom end but sound just as good.
The Mark IV is a great amp but is a bit different than the Mark V. In order to get similar compression with the Mark IV as you can get with the Mark V you need to push the master volume up to 4 (3 is at full peak output, anything higher compresses the tone considerably). Note with a Mark IV combo, you cannot do that with the MC90, it will break up severely. A Fane AXA Studio 12L takes a lot of abuse and I can literally set the master volume as high as I want, signal becomes more compressed as you get passed 4. Tone wise, the Mark IV basically has only one voice per channel. RHY1 (clean) is nice and dry (using combo speaker and 1x12 external cab). Similar through the 412 cabinet. RHY2 was a channel I did not use much. It can get muddy easily. However through the 412 it sounds really good. Lead in the Mark IV (without using the phase shift pulls on the presence control and with the lead voicing set to mid gain) can get close to the Mark V in Mark IV mode. What can be done with the Mark IV that you cannot do with the V (early versions of the manual of the V indicated you could, but later changed to you can) use an integrated quad (two EL34 and two 6L6) You do not gain that much and the differences is not dramatic but is a bit different. What I found that sounds really cool with the Mark IV is mixing TAD6L6GC-STR with SED =C= 6L6GC. Channeled into the 412 cabinet can really sound sinister. When using it as a combo, not noticeable as much. I like my combo but the Mark IV as a head would have been a better amp. I will not say one is better than the other since they are both great amps. The Mark V is far more versatile through its different voicing per channel. I actually like both amps and they complement each other running them in parallel with one guitar and a stereo effect used as a signal splitter. For lead work with note definition and articulation the Mark V would be the top choice. I have experimented with triode and pentode modes. If I need more headroom in my signal I will set to triode. Also the three power modes of the Mark V really set up the stage for versatility. 10W mode in CH3 has its merits. I used to use the 45W mode most of the time with the power switch in Variac position. Cuts the highs down a bit. The Mark IV amp, that would be the tweed setting. There is a lot to discover with the Mark Series amps than what meets the eye. How I have my rigs set up, Mark V, I use it for everything (blues to heavy metal). Mark IV, set up for chug metal. (helps to have an oversized 1x12 for deep tones) Chug Metal, not sure that is an accurate term. Perhaps I should become a Bassist instead, I seem to dwell in that frequency range most of the time. The RA100, that is just a raw amp best suited for vintage tones but can do some heavy stuff too.
Reason why I am not working for Mesa, they did not want me, never mind
I never sent them my resume, but I did send one into Peavy and Carvin. The other reason, I am not an audio engineer, my career path took me into a different direction into process controls. Perhaps if I started in the guitar amp designs 20 years ago I would have made some fun stuff, I was more up to par than, now it is just cobwebs, besides I have fun with what I do now, no need to change career goals.
Randall Smith is a generous in his own way. Have to thank his efforts in providing a superior product that we can all enjoy. Not sure why Mesa and EV went their separate ways, either cost or politics got in the way. The EV I had in my Mark III was part of the reason it was a great amp, the other part it was a Mesa. If they still had the EV black shadow available I would be using it now. I know the basics with the tube amps but that is it. As far as information, I only skimmed the surface.