I've recently tried a bass amp (without using a pedal) at a shop and it really sounded like Iron Maiden's Steve Harris' tone, so I bought it. When I tried it at home with my bass it still sounds just as rubbish as it used to with my previous amp. I've got a pair of high gain pickups (similar to Seymour Duncan) but it makes no difference at all in the tone. I'm wondering if it's something to do with the strings or even something else. By the way, my strings' gauge is 0.40. Any help will be much appreciated, I really don't want to feel like I've wasted my money buying this amp.
The actual bass you play on has a huge effect on your tone; debatably more so than the amp. I did some reading, and Harris plays mostly on Fender Precision basses, which are known for their thick tone. He also uses thick gauge strings--.50 to .110 if I'm not mistaken. I also use heavier gauge strings, and they play a large role in providing a larger sound.
So, upgrades to your instrument or strings would help, but I still wouldn't say that you wasted your money buying the new amp. Play around with the settings on your current bass and the settings on the amplifier and see if you can find combinations that thicken the tone. Adding distortion or overdrive often helps.
Steve Harris' tone comes mainly from his use of fresh flatwound bass strings. Rotosound actually make a Steve Harris set (Rotosound SH77), so that would be your safest bet.
Likewise Seymour Duncan make a Steve Harris signature pickup (SPB-4) and Fender make a signature bass for Steve. I don't think his amplifier setup is especially complex either; simply Ampeg SVTs and possibly some compression somewhere down the road.
Steve uses very low action and an incredibly light touch. I've read in articles that others have picked up Steve's bass and not been able to play it without fretting out on the neck, because they aren't used to playing so light. It seems like an oxymoron, but having a light touch means you can play long sets of heavy music!
There are isolated bass tracks of Steve's on Youtube. When they first appeared people thought they were fake, in part because of the tone and in part because of some of the sloppiness of the playing. On the classic Iron Maiden records Steve sounds wonderfully consistent, but I suppose when he's running around onstage (from memory the isolated bass tracks are from live shows) it maybe isn't such a precise art. In short, you need a bright bass tone derived, in part, from the use of fresh flatwound strings. You don't need much, if any, overdrive. You need a light touch and a mechanical consistency, as well as the stamina to play triplets with your right hand for two or more hours at a time.