Not sure how accurate this is but:
Sykes plugs straight into his Marshall JCM50, with no pedals or outboard effects between the amp and his Les Paul. “John’s very particular,” says Gaillard. “I once said, ‘Can I put the tuner in line for you, so if you’ve got any problems it’s a lot easier?’ And he said, ‘Oh no, I don’t want to start introducing more cables and I might lose some signal!’ So I just put a tuner in front of him with a cable hooked around on the mic stand, and he said, ‘If I want to, I’ll just unplug my guitar, plug the tuner in and say a little bit of bullshit on the microphone while I tune up!'”
JCM800's can gain up pretty good if you get the master up and dial back preamp for some tightness and I suppose with hot pups that might be what we are hearing because he def. isn't playing as gained up as he did with Whitesnake. He's working harder for those lead lines in this clip.