Vox, mic placement, get your gain staging right, try a flattering mic that sounds like it is not hooked up to a slight phasing effect, a good clear flattering signal, the high end should not be too loud yet it should be clear and un muddied by too much low end swamping the preamp. You can accomplish that without EQ if you have decent gear, or you can subtract a little lows in the right area if they are swamping. Cheap mics can sound tinny so you might have to lose a little high end to accomplish it if you have one of those. If the dynamics are too wide for the preamp causing unflattering distortion(as opposed to flattering distortion), compress starting at a low 2:1 ratio or lower. Two passes through slight compression is better than one hard compression ratio in most cases with vocals and less noticeable. Once you have that clear track in place, you might decide on what kind of reverb you want, natural sounding which encompasses certain parameters, or an un-natural sound which you would either need to be able to describe or not and just experiment. If you are looking for a natural sound, predelay (which determines the "perceived" room size) is between 0 and 31 ms max and reverb of 0.3 sec to any length with high end roll of set to 5 khz. Tighter times being more like ambience, longer times being like halls rooms, or theaters. Any cheapo reverb unit can accomplish this so don't frag your old unit till you start using it like this. you can roll off the low end below 300 hz of the reverb unit return too to clear it up too.