I agree, I don't think a battery box would color the sound at all, I mean we are talking about a few resistors and some caps. It’s not like you are building a preamp, that will as you say color the sound. The battery box should sonically be better. I would think, I mean with a preamp you do get increased headroom and more sensitivity and with the Fletcher Munson curve, you might think that you’re getting more top end with the preamp but that's just a mater of gain/human perception. Not of actual facts. The signal is the same or close to the same if the preamp in question is as good as I assume it is. Its just that your getting more gain and hearing more sound IE the perception that the sound is in fact better I would do a test with the bat box and the preamp. I would set the preamp to unity gain and confirm that it is at unity. Then I would set up the batt box with the same signal and fixed mic position, so that you remove the fudge factor and listen again. I am sure you will notice the sound of the batt box to have more depth. Unless you have a bad design in the batt box where the value of the blocking caps is not high enough, I like 10uf my self for a batt box. Sound is so freaking subjective sometimes you fool your self into thinking that X is happing when Y is.
Welcome to the wacky fun world of psychoacoustics. I use my ears to listen to the stuff I make but I also use test gear just to see if my ears are not lying to me. But hey I am off in a tangent I will shut up now
They sound different
The MMA is a preamp its much cleaner then the MPS 6030 which is a battery box ...
In find this interesting and wrong. A battery box is not adding any additional noise or gain, thus it should be a cleaner and less noisy signal. Even the best preamp in the world will add some color, noise and distortion. my $.02