Recording Acoustic Guitar

Ok, so I've been doing this for about 20 years now.  And one thing that has always bugged me but I've never asked anyone else about....why do I have to max the input gain of my pre-amp, max the output of the pre-amp, lower the threshold of the compressor to almost nothing, and max the output of the damn compressor - just to get a flimsy signal that still sits about 9 to 12 dB lower than it should be?
 
Why do I have to max EVERYTHING, every pot, in every box in the freaking chain to unnatural settings...just to end up with a weak signal that couldn't clip if I beat the strings with a hammer?  (Not that I'm trying to clip, just a reference as to how low and disappointing the signal is).
 
I set my SM57 about a foot or so from the output port of the acoustic, and feed that into a small tube pre-amp (Art Tube MP) and feed that into a Behringer Compressor and then out to my Soundcard.  
 
Does anyone else have this issue?  Is this common, to have to max everything in the chain and still not get a juicy signal?  I have the same problem recording bass, direct in as well.  Same chain, pre-amp to compressor to soundcard, and again, I have to max every piece of that chain and still end up with a low, weak bass signal.  
 
Irritating.  

The sm7 needs a lot of gain, as Kalle sez.  You need to 1. use a different mic; 2. get an outboard preamp w/ lots 'o gain.
 
Here at home, even w/ a limited mic cabinet,  I'd first try a small diameter condesor - in this case an Oktava Mc-012.  They used to be cheap, but you can find on ebay for $250.  That is about as low as I know for a sdc that I've used and sounds pro.  A good sdc is useful on all sorts of acoustic stuff, and female vocals, chorus etc.
 
If you don't need to record other stuff and the sm-7 works for you except acoustic guitar, I'd get a better preamp.  I've got the mp and it is OK (basically the same preamp design that is in every interface/cheaper mixer w/ a starved-plate tube hooked in there).  If you use the tube to up the output it gets pillowy (technical term) before crapping out.  Neither of which is optimum for acoustic guitar, I would think.  The first preamp that comes to mind that I know is the Focusrite ISA One.  80 dB of gain will stoke that sm7.  You should fine everything sounds better w/ it - vocals, and you can use the preamp and DI simutaneously (tho only 1 transformer for the preamp then).  It is kinda of a goldilock preamp, not too clean, not too colored even when pushed.  If you wait until Christmas Guitar Center usually has a 20% off so you can pick one up for $400 + tax.  There is also the Warm Audio preamp at that price range, which is just as good but a bit more vintage sounding.  Either of those would drive your dynamic mic and add a bit of transfomer roundness to your digital recording.  Neither one of them you'll get rid of even if you win the lottery.  There are other mic preamps, some cheaper, but I ain't used them so I can't comment on having enough gain.  But there is the GAP, Electro Harmonix which range from a few hundred to over $300.  Rane and ashley are cheaper yet, but check the specs for gain.  You need a lot for the sm7.

Hey guys, stuck at work and can't comment much but wanted to thank you all for the replies.  Much appreciated.
 
I have a KSM27 condenser mic, that I use mainly for vocals.  Since it didn't sound so good picking up my acoustic (to my ears anyway) I guess I thought all condenser mics wouldn't sound so good for it.  Bad assumption.
 
I will take your advise, read through your suggestions and give this a try.  I think I am putting WAY too much faith in the SM57 to do everything I need.  

Voda La Void
a small tube pre-amp (Art Tube MP)

You need a preamp with a lot of gain to get your signal up. The Art Tube is not that preamp.

<devils's advocate mode>
 
Most of the suggestions requiring new equipment are accurate, but possibly not immediately useful<G>... if that makes sense.

I am not a big fan of the ART preamplifier, but I'm thinking you can probably get a better result with a little elbow grease.
 
Step one - ditch the compressor... sometimes a compressor can help smooth the rough edges, sometimes it can be used as an effect, but it is highly unlikely that it is necessary, and quite possible that it is fighting you.
 
Acoustic guitars are NOT quiet instruments, or at least they don't have to be, and all of mine can easily overload the amplifier in a condensor microphone with very little effort!
 
And finally, there is nothing wrong with an SM-57. It might not be my first choice for an acoustic guitar, but heaven knows I've recorded some decent tracks using an SM-57, and more to the point, doing so taught me a LOT about recording. One of my mentors (whose name you would certainly recognize) used to brow-beat me to remember that the first equalizer and compressor in any recording is the selection and placement of the microphone(s).
 
So let's tackle this from the top, using just the equipment you have...
 
Start by listening to the guitar - not meant to sound mean, but really listen to the guitar. If you can get someone else to play it you'll have an easier time, but in either case, try to find a spot where it sounds like the sound you are trying to capture.
 
Now stick the microphone in that spot. Experiment with the distance between the microphone and guitar. A LOT!
 
OK, now that you've taken care of the important part it's time to worry about the levels, because something sounds hinky there. The SM-57 has a pretty decent output level, so you should have no problem hitting the clip point, which makes me curious<G>!
 
Can you try different cables between the microphone and the preamplifier, and between the preamplifier and the sound card? You may find that one of your cables is mis-wired.
 
Next up, find out if your sound card has a balanced or single-ended line input. If you connect a single-ended input to a balanced output you could lose 6dB of level... and that could be a problem. Also, make sure the preamplifier is working properly... while it isn't the best device on the market, the ART is competent.
 
Last thought... I use ribbon microphones, large and small capsule microphones, and moving magnet dynamic microphones (technically ribbon microphones are also dynamic) all the time, depending one what I'm trying to accomplish. And in fairness, my collection is sufficient for my purposes - but it has taken me 30 years to build the collection. (And I still want a pair of Schoeps CMC6/MK41s and a pair of KM-84s... there's just no satisfying some of us<G>!) My point... which I started with anyway... oh yeah... have fun with placement. One of the odder tricks I've learned is to place a microphone above my shoulder, at around ear level. The guitar sounds markedly different to the player and the listener, and sometimes you want to capture the players experience.
 
Two microphones is, in reality, probably better than one, but starting with one will teach you a lot. When you have two you can extend your experimentation by combining some of your favorite single microphone techniques.
 
Good luck, and feel free to ask questions...
 

Kind of a misconception that LDC's are better at bass reproduction than SDC's.  The larger capsule has a slower recovery rate and transient response which will make them sound more boomy and compressed (but musically so) than SDC's.  But you also loose detail by comparison.  Even great LDC capsules like the M7 will start loosing low end around 60Hz where any decent SDC will be flat until at least 10-20Hz.  Regardless, the acoustic guitar does not reach low enough to warrant fear that any condenser mic will not be adequate.
 
Some of the best and most popular mics for guitar in any style are the KM84's,  Schoeps MK4 capsules, and to some degree the AKG C451b which is luckily the most affordable of the bunch.  In classical, we do tend to prefer omnis.  The Schoeps MK2, Neumann KM130's/83's, and DPA4006 are standards.  My favorite are my Josephson C617set mics, which have the best detail of any mic on the market, but should be used in a good room only. 
 
If you want something affordable, believe it or not, look at the Behringer SDC's.  They actually compare very well to the modern KM184's, and in a recent blind shootout on GS, they were picked over the Neumann's about 70% of the time. 
 
Ribbons can be very nice also.  They will allow you to focus the sound and attenuate enough of the high end to make string and fret squeaks less of a problem.  But you still need tons of gain unless you find an active model. 
 
I do advocate for not getting in too close, of course.  15 feet is comical overkill as Jeff seemed to insinuate, even though I do know a few people who would try it, but it is good to find a balance between presence, mechanical noise, and room.  For country or folk music, one of the most common setups is a condenser 2-3 feet in front of the instrument and another over the right shoulder facing down toward the body. 
 
Hope this helps