I have a small home studio setup.I'm using a focusrite interface and dynamic microphones as SM-58. I feel as if the recorded signal is not big enough and I always end up having to push some Pro tools plugins to make it sound better. The final result is a bit crap and sounds too processed. It's like I don't have enough signal to work on.
It sounds like your problem is you've been told (as we all have) that the quality of a recording is determined by the quality of the recording equipment, which is completely false. The quality of a recording is determined by the skill and experience of the recordist.
You wouldn't post a question saying, "when I play bass, it doesn't sound like Les Claypool. Do I need to buy the same bass he used to play the same way he does?" Of course that's ridiculous. Recording is an art form similar to playing an instrument. Giving someone who has never played bass before Les Claypool's bass won't make them a good bass player, and if you hand Les Claypool an MIM Squire P-Bass he will still be an awesome player and he will make that bass sound as good as it can sound.
The same thing is true with recording. A recordist who has been learning and recording for 20+ years can make great sounding recordings with almost any equipment. Someone in their first year of recording things is still learning and is going to struggle to get good sounds no matter what microphones, etc. they are using.
To improve the quality of your recordings, you have to improve your skill at recording. Buy books, study, read web sites and forums, check out YouTube videos, but most of all: Practice Practice Practice. Practice recording every day, if you can. Move the mic around. Listen to what happens when you change things. Develop your ears. Recording everyone and everything. It's like learning an instrument. It takes time and dedication and it's very rewarding.
The only result of 'not enough signal' would be a raised noise floor as a low level was brought up. And I don't think that's what you're talking about.
No, you don't need a tube preamp to add 'interesting' distortion. A condenser mic will be brighter, but the SM58 was designed to flatter vocals, and still does a pretty good job of that.
Paradoxically, you may actually be recording too loud. A signal that 'hits the buffers' at any point in the recording path will be irretrievably damaged.
Also, make sure your SM58s actually ARE SM58s. The market is flooded with fakes. If you paid a 'too good to be true' price, you've probably got a fake. One test is to unscrew the ball and see if the capsule is mounted on a rubber shock absorber. If it's rigidly fixed to the mic body, it's a fake.
Are you confusing 'better' with merely 'louder'?
Bear in mind, modern pop records go to extremes to get everything sounding as loud as possible by the time they're released. Very few people ever track with all that compression on; maybe a gentle curve on the input, everything else is done in post.
Achieving those high levels at mix/mastering is in itself no mean feat. Whether you love it or hate it, it takes a good bit of talent & expensive gear to push that loud without sounding bad.
Compulsory link to The Loudness War
...and no, a valve pre-amp will not make 'all the difference', neither will a cheap condenser.
A hugely expensive valve pre [eg Manley VoxBox, the single best mic pre I have ever had the privilege of using] & an industry standard Neumann U87 will only help if you know exactly what to do with them to gain that relatively tiny sonic improvement compared to the thousands of dollars' extra investment.
It works both ways. If you take your skill level and use better mics and preamps and better equipment, the results will probably be more pleasing. Turn that around and say you're going to use less than optimal recording equipment, that same recording can probably be more pleasing if you have better recording skills. Generally, we have to work with the equipment and skills that are at our disposal and accept the results until our skills and/or equipment improve in quality. That's usually how we acquire experience and understanding about what we're doing. It's a valuable part of the learning process.
Great-sounding vocals always start with the vocalist. A voice is an insanely flexible sound source and there are so many dimensions to a vocal performance: pitch, elocution, dynamics, and an infinite range of possibilities for your personal style. You can scream, croon, growl, whisper, or lilt.
I usually record rock bands and to record vocals well, I recommend these tools:
- Large diaphragm condenser mic. Neumanns sound amazing but you can get a Perception 220 with a nice shock mount for $150. This mics have tremendous clarity and capture both highs and lows really well. They can be delicate so treat them nicely.
- A pop filter. Certain "plosives" or fricative sounds overload the mic making a popping sound so you put this panty hose thing maybe half an inch or an inch from the mic and it stops the pops.
- Compression. A really good singer doesn't need compression but I've found they really help instill confidence in performers because you can get up close and whisper and then shout your brains out and the compressor will instantly adjust the volume. It helps prevent vocalists from getting sheepish about their performance.
Good bass sound (and kick drums and low end in general) is like the final frontier when you are recording acoustic (i.e., non-electronic) instruments. It's hard to do it well.
To record a bass guitar, I use a direct box and an AKG D112. The direct box lets you capture the signal straight out of the bass (or line out on your amp) and the D112 is a sturdy mic usually used for bass drums. I wish I had a better bass mic and I've been told an Electro Voice RE 320 is even better. The P-220 should also work.
Mic placement for guitar speakers makes a huge difference. To be honest, except for possibly the guitar itself, this is the single most important consideration affecting the sound of your bass recording. I strongly suggest you experiment extensively til you find a sweet spot. Avoid pointing it straight into the center of the speaker or you might get some phasing. Angle the mic from one side a bit and point it straight at the center of the speaker. Start with a 45 degree angle and then move it around. Less angle. More angle. Closer. Farther.
So you record both mic and DI for your bass performance. And OF COURSE you have to play it well. That should go without saying. Make sure there is no peaking or overloading. If those red lights are going off you have a problem. Turn down the gain.
Then, in your mix, you blend the two bass tracks to taste. If the bass is getting lost in the mix, consider adjusting: guitar tone/pickup, amp settings, mic placement. It's better to adjust these than try to fix it later. If it sounds really good in the room, consider moving the mic a bit. It's not unheard of to place a mic back from the speakers to capture the room sound also -- although bass tends to suffer from standing waves. If you find that certain notes are just super loud and tend to fill the entire room, that's probably a standing wave and these make it tricky to record with a mic. Consider turning down the amp and/or moving the mic closer to the speakers.
I would also strongly suggest learning to use compression effectively. A perfect performance doesn't need any, and too much compression can rob a mix of all its energy, making it sound lifeless. But compression can also tame an unruly mix and make a rough or raw recording sound much more controlled. I always compress bass and vocals. If your bass is getting lost in your mix, consider compressing it 5-8db and turning it up.
EDIT: I neglected to discuss amps but assume that you probably have a rig and don't plan to simply purchase another rig. A super expensive Orange or Boogie or Ampeg rig will obviously sound better than a cheap used junker. I like tubes better than solid state. But if you can't purchase a new rig, consider trying a different speaker size. For downtuned metal, you should consider a 15" or possibly even 18" speaker. For funky stuff and most rock at normal tunings, 10" speakers sound good.