A fav from the Maiden boys. From my research he always used SS amps so I dont reckon it's a tube amp. Iron Maiden- Innocent Exile - YouTube Definitely P Bass, then what?
I can't view that clip on a mobile, but I don't think he uses any dirt effects. I've heard he used Marshall and Hiwatt amps in the old days.
It's the studio version of the song Innocent Exile from Killers. Love the album for bass playing and tone, just wasn't sure how he might get that sound from a solid state amp. I dont think he has ever used dirt pedals either. It might just be how that amp sounded driven by a 70's P bass!
Remember though that what's used in studio is rarely the same as what's used live. Plus the engineer may have taken a raw clean DI'd track and then reamped or treated it in any number of ways without the bassist present at all. It's very common.
Certainly, it's been a standard practice since the late '60s, or maybe early '70s. Ever since multi-track recording became the big thing.