I know next to nothing about preamps. So if I am miking a guitar amp, am I going to have to plug the mic into the preamp. Or not? If so, how am I going to plug this into my computer? Through a firewire audio interface or something?
That is correct. The preamp usually outputs to the computer by USB or firewire. The annoying truth that most beginners just don't want to hear is that real mics don't plug into computers. Note this, however- A computer recording interface generally has one or more preamps built in. Although they are generally not the finest preamps in the world, which can cost thousands per channel, good interfaces have components that are meant to work together. So- if you have a $200 interface and a $2000 preamp, it still goes through the Analog to Digital converters in the interface. So- if you upgrade the preamp, you soon learn that you need to upgrade the A-D conversion- more big bucks. Mixers also contain preamps, usually among the cheapest ones on the planet, and some mixers have A-D converters and digital output, so they can be used as an interface. Some recorders also have preamps, A-D conversion, and digital output, and may function as an interface as well. In all cases, I recommend at least 2 channels to start with, to enable stereo recording, or at least the simultaneous use of 2 mics.
Here are a couple of my favorite simple 2 channel interfaces:
I like this one for cheap:
M-Audio MobilePre MK II | 8thstreet.com | Call 1-800-878-8882 | Most Orders Ship Free!
I prefer this, especially if you are a guitarist:
Line 6 POD Studio UX2 | 8thstreet.com | Call 1-800-878-8882 | Most Orders Ship Free!
Then we get into the recorders. This one has a lot of versatility, and a pretty good track record:
Zoom H4n | 8thstreet.com | Call 1-800-878-8882 | Most Orders Ship Free!
So- why would you pay the extra money for a recorder/interface? First, you can take it wherever you are, without the need for a computer. It'll fit in a lot of guitar cases. You can use it for a headphone amp, a scratch pad, on trips, or for remote recording. When you upgrade to a better system, unlike the plain interface, it will still have uses, instead of being sold at a loss. In short, it doesn't become useless. I used a Korg PXR4 Pandora that way for some time, but eventually it became obsolete. The Zoom blew it away.
The H4N has a few other advantages. First, it has 2 onboard condenser mics, and second, the ability to record 4 tracks simultaneously, as long as 2 of them are the onboard mics, or a stereo mic. So- I can record drums by putting the H4N on a mic stand (with included adapter), using the onboard mics as the overheads, and the 2 XLR inputs for kick and snare. This really needs you to have the remote control card, which is an aftermarket accessory, about $20. Or- I can plug a stereo mic into the 3.5mm stereo input, which disables the onboard mics, and use that for the overheads. I use SONY ECM MS-957 for this, which works very well with the Zoom. For higher quality remote stereo recording, I use a pair of AKG C2000B's, which also get along just fine with the H4N. The money I have made selling stereo choral recordings made with this setup has already paid for the H4N and the 2 C2000B's.
By all means, the UX-2 or the Mobilepre will meet your most basic needs, but increasingly, I have become convinced that a machine like the H4n is one of the best self-contained solutions for cutting your teeth on recording. If it's the only piece of equipment you have, you can start recording on day 1.
And, even if you are operating at almost pro level, you will still find uses for it. I've got about $40,000 in the studio, and I still use the little Zoom quite a bit.
As far as the original discussion, if we have all these interface options, why would we want a preamp that doesn't do anything but be a preamp? There are several answers. One- because you need to plug into a recording sound card or digital recorder that doesn't have preamps, and there are still some out there. (do a search on Audiophile 2496 for such a soundcard, and on HD24 for a very cool older recorder as examples) Two- you are trying to bypass, or at least decrease the gain on the cruddy preamps in an otherwise useful piece of equipment, such as an older digital recorder. Three- You are using dynamic mics that have very low output, and you simply need more clean gain than your interface can provide. This is common with ribbon mics, and high quality dynamics such as Shure SM7b. Four- you really are ready to upgrade to pro level or closer-to pro level, and you really want a badass preamp to go with your badass A-D converter.
Really top level preamps are prized for 2 reasons. Either because they make things sound exactly the way they sound (we call this "clean" or "transparent"), or because they make things sound *better* than they sound, in other words, they are flattering, like acoustic makeup (we call this "colored" or "warm"). Do not get confused when marketers try to convince you that a vacuum tube will make a preamp sound "warm", or is somehow necessary. It's just marketing. There are clean and colored preamps, great ones, and awful ones, with and without tubes. In general, if you have a real need for a standalone preamp, I recommend getting 2 good clean channels to start, and then considering more colorful preamps later, to flatter what *you* want to flatter, the way *you* want to flatter it. For purposes of reference, you will also hear the term "channel strip". This is a preamp with one or more channels that also has EQ and a compressor. For the record, mostly I use Avalon AD2022 (2 godly clean channels) and Joemeek twinQ (a mid-priced 2-channel channel strip with an optical compressor).
IMHO, the cheapest standalone preamp you can buy with 2 clean channels that doesn't totally suck is M-Audio DMP-3.
I hope that helps to clear up some of the preamp mysteries, both on the technical side, and the artistic side. Good luck.