Wierd observation between 2/3 prong adapters and speaker/headphone noise

  • I bought a 3 prong laptop adapter for my Spark which eliminated the buzz noise just fine from the main speakers. Today, for kicks, I decided to plug the headphone jack into my powered floor monitor. The sound was awesome but there was a terrible hiss. I confirmed that the hiss was not the monitor, but the Spark.

    I swapped back to the factory 2 prong power supply and the hiss from the headphone port was totally gone. Beautiful clean sound out to the monitor. However, the buzz noise was back on the main speakers. As another data point the headphone port hiss was gone when running off the Krisidonia battery but there wasn't enough draw to keep the battery from automatically shutting down.

    So... not the end of the world, at least I have solutions for both, but why would that be? Headphone has no hiss with the factory power supply but the speakers have no hiss/buzz with the 3 prong?