Enjoy the RA100. Have fun exploring the sonic range of this amp as it is one of my favorites. Actually I though you already had one.
I bought both of my RA100's used. One is mint and the other is excellent. Actually they both look like new. One is a head, and the other is a combo. I love both of them. Very flexible character clean to Hi/lo. If you want heavy you got it, mild and bell chime, it is there, Classic rock OH YEAH
Vintage tweed like tones
(clean channel with gain boosted, drop the bass and raise the treble). You will find the Mid control is the most reactive n the Hi/Lo and the treble almost acts like a presence control since the amp does not have that. Once you get used to the 100W power, switch over to 50W power. For me, the Honeymoon is not over with this amp. Combo sounds a bit different due to the partially open back cabinet.
Having the FX Loop always active is no big deal. But if you want some effects present for certain channels, there are loop switchers. The cable for the Channel selection is open circuit for clean. Tip/ring for hi/lo (not exactly sure which is which). I am not really big on using effects but I do sometimes. Not much for the pedal dance.
Many have claimed the Reverb is noisy, I do not seem to have much noise with either of mine. Combo is quiet since the tank sits on the bottom much farther away from the chassis than the Head. Check for ground on the reverb tank to the chassis. Dark gray or black wire should have ground as it is a coax cable.