This topic has been discussed at length in the forums more times than I can count. You might want to take a look at what is already been said. At a high level, you will note that people have some passion around this topic. There are different types of passives. Resistor based, transformer based, autoformer based, and others perhaps. These tend to be zero gain designs, so that all they can do is attenuate the volume from the source. They do not amplifiy. Resistor designs burn the extra volume off as heat, whereas transformers work by decreasing voltage by increasing current. You need to do some work to ensure that your source has high enough voltage to match the input sensitivity of your amp. Otherwise, you may not be able to achieve the desired volume. Also, especially with resistor passives, you need to make sure you have a match in input and output impedences, and you will need to keep the length of your IC's short. Otherwise, you may experience aberations at certain frequencies. They do not require AC power. They tend to be reletively inexpensive compared to active preamps at a given level of performance.
Personally, I like the transformer based designs (also known as TVC's) but I am not so hot on the resistor based designs. Most of the passive advocates will tell you they like the transparency and low noise of passives. Advocates of actives will claim passives result in a weak sound with no body, and will gladly sacrifice noise and transparency to get that body.
I haven't seen Sam's latest love affair? What piece is he hot on this time?
Personally, I like the transformer based designs (also known as TVC's) but I am not so hot on the resistor based designs. Most of the passive advocates will tell you they like the transparency and low noise of passives. Advocates of actives will claim passives result in a weak sound with no body, and will gladly sacrifice noise and transparency to get that body.
I haven't seen Sam's latest love affair? What piece is he hot on this time?