eyyyyy.
Fist thing that comes to mind is how empty this room is? .. could the 'tinny' sound be the result of a high pitch sound reflection (reverb) off yer walls?
Is the mix of all the mics you're using tinny .. or is the recording of each individual mic tinny? .. are you really using more than 1, or have you limitted your experience to a single mic so far?
How loud are you playing this thing man?
It still has to be pretty loud for instrument mics.
That mg amp, that's solid state right? .. so it doesn't have to be terribly loud, but you need a bit of juice for the 57's.
Try to get some of that ooumph by placing a spare mic in the back of the amp. No shit. ... but read the rest of this first ..
Also, like most of us here, you probably have your amp in one room, and play your guitar in the 'control' room , most likely with a pair of headphones on your head or through monitors.
So couple of things:
- Make sure you record the guitar bone dry (no effects) .. reverbs and delays are added to the recorded guitar tracks AFTER.
- Is your patch cord to your amp too long? Are you loosing too much juice?
- Are you sure it's weak and tiny, could it just be that your headphones or monitors simply can't reproduce what a 4x12 can do ? (uhm that's a loaded question .. of course they can't (depending on how big they are).. but maybe your recording would be great in a mix with a bit of compression and eq'ing. A mic'd cab rarely sounds great in the home recordists control room. Standing in front of it always sounds better. It's always gonna sound weaker. (Unless you're really really really good at the recording shtick .. then maybe you can pull off what i've never heard . The guru's can .. but .. takes years.)
- Double tracking (recording the same thing twice and panning one to left, the other to right) is the key to full guitar rythms on rock and metal albums.
.. Beauty with this method, is that you can use a single microphone everytime, but record many takes of the same riff. More time consuming though. (Managing 1 mic, is easier for us home recording guys, though some of the guys on the board are more knowledgeable and have the ear for mixing several mics.)
- Try making the amp louder .. and make sure your recording signal almost hits the red .. almost.
That's all i can offer.
Trist