I must be missing something with my V..... It is not tight or mid heavy but it is extremely bright with stock tubes in it... If the V did not respond well with preamp tube changes I would have gotten rid of it long ago.... Always run the 90W mode too. I do not like brittle tones and the Mark V seems to be abundant with that. Had to adjust bias resistor so I could run the Mesa tubes without red plating. Sound great now but still not overjoyed with this amp like many others are. I should try out another one just to compare.
I actually thought the Mids are more present in the JP-2C. Run the amp without the 5band EQ engaged, also note that the amp does not suck without the 5bandEQ turned off like the Mark V. At lower volume settings the JP-2C has a bit more sag and would be about as spongy as the Mark V or even the Roadster. Once the volume CH2 or CH3 is above noon, region where the amp really begins to wake up, the mids and higher frequencies become more apparent and balances out the bottom end. To me the JP-2C is tight, bold and responsive. Roadster and Mark V seem a bit too loose and just do not compare, although I favor the Roadster over the Mark V. Also depends on what cabinet I am using for comparison. Mark V combo running through Celestion 90W Alnico speaker makes this amp sound much better, however though the V30 loaded 412 I cannot stand it as it becomes brittle and not so rewarding. The Mark V was one reason I began to hate V30 speakers in general. The RA100 is the reason why I started to love the V30... Roadster made me dislike the EVM12L as I had rebuilt my old Recto 412 with Black Label EV speakers when my Mark V was a head. Actually the Celestion Creamback G12H75 seems to be the winner with the Roadster and really kicks some *** with the JP-2C. Best paring with V30 would be the RA100 or the JP-2C in a 412.
I would probably agree with Samuel about the mids being more abundant especially with increase on presence and with some adjustment on the 5Band EQ. I have been exploring many different settings on the JP-2C and so far I have yet to find it disappointing. I am sorry for those who are not getting that magic from their JP-2C as I am. I am not on drugs either that would influence my opinion how something sounds. At the moment I have the JP-2C, Mark V, Roadster, RA100 (head and combo) to compare. the JP-2C is just blowing me away. Just last night I was trying to dial in some classic rock tones for ACDC or Led Zeppelin of which I always thought were better served up with the RA100 half stack. Nailed it with the JP-2C or at least close enough.
As for the FXLOOP, it works quite well with all of my pedals including the Line6 DL4. I tried all of those that seemed to compress or degrade signal when used in the Mark V loop. Strymon works on both equally well. No tone sucking, or added compression with any of the pedals I have used. the list of delays I have: Strymon DIG, Line6 DL4, TC Flashback, Boss TE2 Terra Echo. Reverb Strymon Big Sky, Chorus Strymon Ola. I even tried the Wampler Plexi Drive on the clean channel. I will have to explore that in more depth since I have it and never really needed to use it. Not that it is necessary as the JP-2C can really provide long sustain but I did experiment with the Strymon OB.1 compressor and was not disappointed with that either. I believe the JP-2C is a better workhorse than the Mark V, even though it does not have 9 different voice settings like the V (some of which I found unusable due to extreme brittle character or breaking glass tone CH1 Tweed, CH2 Edge. The Roadster actually did the tweed voice properly as that is one of my favorite, I can get similar character with the RA100 clean with the gain boosted. Mark V CH2 Edge, sounds like poo. I have yet not figured out why many like that voice. Perhaps I should plug my 6 string bass into the Mark V and see if that makes a difference. In some ways I envy those that have a Mark V that actually sounds and performs great, not any more as the JP-2C seems to be the holy grail of tone that I can only wish my Mark V would deliver. Only two Mesa's I bought used are the two RA100's and both of those are amazing amps. Everything else was bought new. From the Mark III combo, Mark IV combo Mark V head, Roadster, RA100 head, RA100 combo, JP-2C head, OS Recto 412 (2000) OS Recto 412 (2014). The only two disappointments were the Mark V head and the OS recto 412 I bought in 2000. Everything else has exceeded my expectations. Perhaps the JP-2C is similar to a blend of the Mark III, Mark IV, and the Roadster with a touch of RA100. CH2 and CH3 of the JP-2C can be similar to the Mark V CH3 Extreme and similar to the Mark IV mode. However, what the Mark V is lacking is the true character of the Mark IV and the Mark III. Perhaps the Mark V is a bit sterile if you can control the brittleness.