That *is* is a little odd, if you were using all the same equipment
with the same settings. Same mic, cable, phantom power (or not), knob
positions, etc. I'm assuming that's what you mean. the only other
thing I can think of in that regard is whether the subject was the same
distance from the microphone or the pickup volume of the instrument (if
you're going line-in) was set to the same level. Wierd.