"rtl_fm -M am -f 50.5e6 -r 12k -g 39.2 -E edge -A fast | aplay -r 12k -f s16_be -t raw -c 1" (without the quotes)
Starts up like this on my Ubuntu 14.04 LTS Laptop:
Found 1 device(s):
0: Realtek, RTL2838UHIDIR, SN: 1.3-56.3
Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Tuner gain set to 38.60 dB.
Tuned to 50764000 Hz.
Oversampling input by: 42x.
Oversampling output by: 1x.
Buffer size: 8.13ms
Exact sample rate is: 1008000.009613 Hz
Sampling at 1008000 S/s.
Output at 24000 Hz.
Playing raw data 'stdin' : Signed 16 bit Big Endian, Rate 12000 Hz, Mono
underrun!!! (at least 258.228 ms long)
And sounds just about as good as my AM receiver does for picking up Power Line noise with almost no impact on CPU load. I can barely detect it frankly.
I will probably attempt to add this into the Driveby System's Web GUI control panel so that I can have some preset's to switch to on various bands at the click of a button.