The SimpleP48 while excellent in most other aspects, is very dependent on having absolutely clean phantom power if you need it to be hum free. Most mixers have some ripple on the phantom supply. Because of the unbalanced current draw of SimpleP48, that ripple is not cancelled out by the balanced mic preamp.
With my Zoom R24 the high level of hum makes it completely unusable with SimpleP48. No problem with other types of microphone.
With my Mackie mixer there is a low level hum, only a problem on really quiet sources. If I turn off phantom power on the Mackie, the hum goes away and the Simple P48 is hum free and works perfect for a while until the phantom supply capacitors gets slowly drained.
