MP 1,1-5,1 Weird whistling from speaker plugged into headphone jack

[RAMtheSSD]

I am sure that I have read something about this before but I could not find it again --even if it was the same problem. I have a small speaker plugged in to the headphone jack (easy to switch to headphones when I need to vs stereo speakers etc...) and there is an annoying whistling that is barely there most of the time but silence everything and it is seriously annoying and loud! The speaker is fine and does not make the noise when plugged in to the MBP. The noise cancelling headphones must be cancelling the sound somehow but it happens with other speakers. Anyone else having this problem or have any idea as to how to solve it?

 

[tommy chen]

the headphone out of the cMP isn't a line level output as the rear one

 

[RAMtheSSD]

IndioX, thanks for replying. Please expand on your answer; how would not being a line level output cause the whistling?

 

[MarkC426]

Do your speakers not have a headphone socket.
Connect speakers to rear line out preferably.

 

[tommy chen]

simply:

the headphone out is to high because of an additional amp

edit: add a backgroundlayer in the picture

 

[RAMtheSSD]

I need to come by here more often. Indio, that makes perfect sense for the front jack (dark theme is ruining your kickass graphic) but that would mean that the jack in the back would not whistle ever and a different, subtler, whistling is there too. The only thing I have found that either makes it disappear or moves the sound to a frequency I cannot hear is to charge the speaker from either the laptop or the wall rather than the first open USB I find. Cheap headphones don't whistle but expensive ones, not powered but noise cancelling, do. Neither one of those things makes any sense. I get what you are saying (the graphic really helped, thanks) I just can't connect that to USB charging.