Nick, I'm not sure you are getting it. A microphone preamp is not an FX box. It's purpose is to make the signal from a mic stronger, not to change it's sound.
However, some preamps introduce selective distortion, a very subtle effect. We call it "warmth" when we like it, and "muddy", when we don't.
Vacuum tubes (valves, if you are British) are often used to achieve this "warmth". There are 2 main types of tube amp- a pure tube amp, where the power section uses tubes, and the hybrid amp, which is basically a solid state amp where the signal is routed through a small tube in the front section of the amp. Such amps usually have a "drive" knob, which allows you to control the amount of that signal going through the tube. Such amps are often called "toob" or "tewb" amps.
The hybrid concept is one that has not really come of age, and most of them aren't that hot, frankly. It does, however, allow a marketing geek to put "tube amplifier" on the front panel, to sell it to people who don't have the money for a real tube amp, which are damned expensive. Probably the best of the cheap hybrids are Studio Projects VTB-1 and DBX386. Both are useable, but neither is likely to be used on the next pop platinum CD. Expect that real tube mic pres will start at about $500 per channel, and go up from there, way up.
What will shock you, when you get to hear one of these badass tube amps, is how subtle the effect is. You will find yourself asking, "that's all you get for $3000?". The real effect becomes important when all the other factors in the signal chain are taken into account- the room, the mic, the singer, the material, the mix, the cables, A-D conversion, and yes, the mic pre.
OK, back to your issue, which I surmise is- how do you get that crystal clear, up front vocal sound that the big boys get on commercial recordings? Bad news here. There isn't a $300 box you can run that signal through that will manufacture that sound. How they did it is a hell of a lot more expensive, and a hell of a lot more complicated.
First, they started with a badass singer who is very familiar with the mic he/she is using, and can get the best out of it. They selected a mic that suits that singer's voice, especially on that song. That could be a good cheap dynamic mic, or a $10,000 Manley. They placed this singer and this mic into a carefully chosen acoustic environment. In many cases, that is an anechoid chamber/vocal booth. This produces almost no reflections, so the sound of the room around the singer will be created electronically. In other cases, which I often prefer, they used a room with a certain amount of reflection that sounds good, rather than a dead room. Also, some of the boxes used to create a room electronically are in the thousands, pricewise.
Then they used high quality cables to hook this mic to a high quality (read expensive) preamp, set all the gain controls for a strong signal that doesn't overload any component in the signal chain. Then, highly skilled (hopefully) mixing and mastering engineers dissected the frequencies of the whole mix, removing noise, eliminating frequencies where more than one source are competing for the same acoustic space. They set the relative and absolute
level of every signal, and panned them, determining which speakers the sound will come out of. They balanced it dynamically, using high quality compressors, and a mastering room and monitors that facilitate the process, and which cost many thousands of dollars.
My sad news is that there is no mic, no preamp, no FX box, that will do that for you. So what to do? First, accept that pro sound is achieved more by engineering and performance expertise than by gear. Second, accept that even with that expertise, thousands of dollars worth of gear are required.
Third, accept that you currently have neither the experience or the budget to leap to where the pros are. You have to crawl up that flight of stairs, not take the escalator. Start by finding a room that sounds good, and somebody worth recording. Then get a few mid priced mics that work some of the time for some of those badass pros. Get the best mic preamplifier your budget will allow, and accept that you will upgrade later. Get a good cheap multi-FX box, and a good cheap compressor. Then learn how to use them. That will take *years* not days. By the time you have done that, you will have invested the price of a small house in gear. But that's alright, you won't need a big house after the divorce. And you will be an audio engineer and know the answers to the questions you are asking today. I can tell you that I have only recently achieved the ability to get a little of that vocal sound you seek, and it has cost me $40,000 in gear, and 3 years of my life.
Yes, you need a good preamp, but even expensive ones, you will find, are not magic wands. You have to build the whole package of expertise and gear, by steps, over time. Good luck-Richie
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