I played a JC120 for 5 or 6 years. The clean sound is great. The difference between JC clean and Fender clean has a lot to do with the top end. I would describe a Twin's top end as more "chimey" while the JC's as "tight".
Be warned that this is a very loud amp. I never turned it up past 3 or 4 in a 4 piece rock band with the other guitarist using a Marshall half stack. It stays clean loud too, headroom for days. On the other hand, my amp's volume control under 2 seemed to roll off exponentially basically turning the amp into a loud or off beast, so no good for bedroom practicing. But I should mention that mine was a very old one, made in the USA if I remember correctly.
The tone controls are fairly responsive and the chorus/vib is just awesome, however the attack is very stiff. This works well for clean/jazz type tones as the prominent attack cuts through but works against getting a good overdriven tone even when using pedals. I think this is where JC's got the "sterile" reputation. I tried the following pedals in front of the amp and just never was 100% satisfied: Sansamp GT2,
Boss DS1, Boss Blues Driver, Ibanez TS9, Big Muff, Vox Tone Bender, and an old Zoom digital distortion pedal (forgot the name). The best results were with the Sansamp and I really would've liked to have tried a tube pedal in front of it to see if I could get any sag out of it.
I sold the amp for the first Line 6 Flextone series which was a huge mistake and I've missed it ever since. I'll pick up one of the JC 90's one day which I think would be a little more versatile in usage in the bedroom and on the stage.
