Vivian Campbell

Viv Campbell used the RG100ES head during the Dio years and on tour with Whitesnake.

I used Engl Ritchie Blackmore heads for all the solos on both records. When we tracked, I cut the first rhythm with the Engl as clean as I could. Then I went back and did a second rhythm with a different amp.

Jeff [Pilson] has an amp called a Naked [by Friedman Amps], which is a custom-made boutique amp that I believe is based on an early Marshall JTM45. I’m always using my Les Pauls, primarily my Dio-era Les Paul that I did the Holy Diver album with. That and my other Les Paul, which is the Custom Shop model that came out last year.

Spotted at 1:58 in Viv Campbell's "Hot Guitarist" video.

According to Guitar Geek, Vivian uses Celestial Vintage 30s in his cabinets.

Spotted at 2:14 in Viv Campbell's "Hot Guitarist" video.

Vivian uses two Marshall JMP-1 preamps, according to Guitar Geek.

According to this Guitar Geek rig diagram, Vivian uses an Engl Midi Tube Preamp 580.

Vivian uses four Engl 4x12 cabinets, according to this Guitar Geek rig diagram.

Vivian uses two Engl 850/100 power amps, as shown in this Guitar Geek rig diagram.

In the video titled "This Amp Can Do Everything" by Rhett Shull on YouTube, it is shown that Vivian Campbell was among the first people to purchase the Soldano SLO 100 100-Watt Tube Guitar Amplifier.

When asked about the pickups in his Les Paul Deluxe he says, >“I was using DiMarzio X2Ns back then because I was playing through a JCM800 Marshall and there just wasn’t enough distortion in that amp, so I front-loaded it with really hot pickups and Boss overdrive pedals.”

Also in the music video for When Love And Hate Collide, Vivian can be seen playing in front of a JCM800.

This Reverb listing states

Def Leppard guitarist Vivian Campbell used this JCM900 SL-X head on tour with Def Leppard from 1996-2002. Slight remnants of his "Parental Advisory Explicit Noise" sticker can still be seen on the faceplate. Vivian's Marshall amps from this era had this sticker placed over the "JCM 900 SL-X" label and can be seen in the video screen grabs in the photos. Vivian's unique amp settings remain marked on the faceplate in grease pencil.

Vivian Campbell, the guitarist for Dio, is known to have used the Mesa/Boogie Mark IIC++ Head, a modified version of the amplifier that included the “++ Mod,” which increased the gain in the Lead Channel. This modification was performed approximately 20 times by Mesa Boogie before the end of the IIC+ production, as noted in the source titled "A history of the Mesa Boogie Mark II series."