Sparky hit the nail on the head, from my experience with the nady adjust the transmitter if needed (mine when the mp3 player was at the max it would cut out or have poor sound) once adjusted you will be set, just set your amp just a little over what you may need and use that setting all the time (I also use 1/2 to 3/4), then use the mp3 player to adjust volume up and down. I haven't tryed the azden but from the reading i've done most are leaning towards the nady (static and no adjustment with azden, but again I haven't tryed it). I use the nady 151vr but have heard the 351 is better. with that said have a look at the Nady DKW1, it can be run off 12V (same battery your already using) instead of 9V, you won't have to carry as many different batteries.
Here is a link to nadys site to learn more on the 2 (151 and 351) http://www.nady.com/products/video_pg.html. I haven't researched the DKW1 so don't hold me responsible but Its cheaper and 12V (only going from what others say). Do a little leg work your self and you will be happy. One thing I do know is the patch cable you use between your mp3 player and your transmitter works as an anntena so don't ball it up or hide it in your jacket, strech it out and try to point towards the call.
I hope some of this helps, if not send me a private message and I'll give you anymore info I have.
Good luck and happy calling /ubbthreads/images/graemlins/grinning-smiley-003.gif
