Ask the brass player to raise his trumpet to his normal playing position. If it helps him to get into a natural position, ask him to play a few notes.
Place the microphone between two and six feet away from the trumpet player. Placing the microphone closer to the trumpet will result in a tighter sound; farther away will result in a more dramatic and spacious sound.
Angle the microphone about 30 degrees off axis. This will ensure that you are picking up the trumpet's full tonal range. Bringing the microphone slightly above the trumpet player, angled downward, can also help, as this is a trumpet player's normal playing position.
Switch the minus 10-decibel pad on your microphone to on. This switch will be located at the bottom of the microphone, typically in the front. The pad will lower the recording volume of the microphone by 10 decibels so that it does not peak when the trumpet is played.
Ask your trumpet player to play his loudest. Use your audio mixer to adjust the volume of the microphone input. If the sound is too loud, move your microphone farther away from the trumpet player.