I am in a band and don’t have a massive budget. I am thinking of getting a Shure SM58 mic but do not have enough money to get a PA System for it. I am thinking of getting a cheap guitar amp and plugging it into there. So do I get a lead from the mic straight into the amp or a mic into a pre amp into the amp? Which would be safer and produce a better quality sound? Any answer would be greatly appreciated
Assuming the SM58 is low impedance - a lot are, then a transformer recommended by Todd will at least get the right signal going into an amp. with high impedance inputs.
However, point 1. There is little point in spending over £100 on a very good quality mic, and putting it through an amp. that won't do it justice. And it won't. Guitar amps are eq'd for guitars, not mics. They also have max 2 inputs only.
Point 2 - A half-decent quality mic. will still do a good job - one I often use is an old karaoke mic with a <£4 replacement capsule. I'd look out for a pre-loved (as usual!) p.a.combo. I use a couple for keys, Carlsboro, 90 watts each, cost <£50 each. One would do - 6 inputs, self-contained, and actually does a good job for guitar/bass as well. So there's your SM58 budget, but with a good sounding p.a. to boot, that will go on to other uses when you finally get that 2,000 watt rig. It would even make a good foldback...
You want an XLR mic cable and also one of these:
Plug the mic into the cable, the cable into this thing, and this thing into the amp like a guitar. I've done this many times in my youth, when I had no money. It will be more prone to feedback and sound quality will be pretty bad, because of the guitar amp, not the cables. If you can get an FRFR amp, that will sound much better.