John_1 is certainly right that not all passives are equal. Not only parts quality but the choice of attenuator matters. Most agree that stepped attenuators based on rotary switches are superior to potentiometers--though makers and users of very expensive pots will disagree. But assuming stepped is best, it can be series, shunt or ladder configuration. I see no excuse except money-saving for series, though some very prestigious active preamps--the CAT's, for example--use them. The switch matters too. Elma is good, but Shallco is impossible to beat in my experience. A DIY passive can compete with the best commercial ones available, and if you don't use more than two sources, it can be quite simple. But as others have said, your sources have to be up to driving a passive. However, if they aren't, why not aim for ones that are? The money you save not buying an active preamp should make this a practical option.
