I've sort of hit a wall on this audio project and I could really use some advice.
Here's the deal. I have 9 Sharp GP2Y0A21YK0F Analog Distance Sensors hooked up to an Arduino Mega Board. I am currently powering the board with a 9VDC wall wart (actually putting out 12V) going through a voltage regulator circuit that is putting out a clean 5V (there is a 220 uf capacitor in this circuit, so I am pretty confident that there aren't any ripples in the current). The positive rail of the voltage regulator circuit is connected to the Vin Pin on the Arduino and the Ground rail is hooked up to the GND Pin. Then I connected the GND Pin and Pin 11(audio output) to a 1/4" audio out jack.
I have already soldered the positive and negative outputs of the sensors to their respective rails on a circuit board. I then have these rails connected to the rails of the voltage regulator circuit. Everything seems to be fine with the circuit until I connect the sensors. They introduce a lot of noise that I can seem to get rid of. It is not a hum type of sound, but rather a oscillating sound, somewhere around B5.
I am pretty certain that is a ground issue as the problem goes away when I connect the audio to a grounded DI Box, but I would prefer to figure out the problem in the circuit first.