USB ports not equal on my mid-2014 15"

Discussion in 'MacBook Pro' started by krick, Sep 3, 2014.

  1. krick macrumors regular

    Jun 25, 2009
    I've just noticed some odd behavior with the USB ports on my MBP. Up until now I've used the ports exclusively for charging/syncing my iP5, charging my bluetooth headphones (Plantronics BackBeat Go 2) and connecting/powering an Apple superdrive, and I've not noticed any difference between the two ports. Today, however, I plugged in my portable DAC (HRT microstreamer) and noticed two things:

    (i) with the left port I have to fiddle with the cable connection to get power to the DAC whereas with the right port I don't have to at all (I've tested this with both the same cable and with 3 other cables and it's always the same - no power issues with the right port but always have to fiddle to get power using the left port); and

    (ii) the volume level is different between the left and right ports (although not always the in the same way - see below). ​

    I've reset the pRAM to reset the USB mapping and that switched the level balance from being left-heavy to right-heavy (i.e., at first the left port was louder and after resetting the pRAM the right port is louder), but it did not fix the power issue.

    In researching this, I've come across some older articles from a couple years ago mentioning that the USB ports on MacBooks were not equal and that there's a "good USB port" and a "bad USB port". Some audio device mfr's have gone so far apparently as to state that a specific port should be used because of this issue. I haven't found any mention of new MBPs from '13 on being affected by this however.

    One other thing I should mention is that the power requirement of the HRT DAC is low enough that it can be powered directly from my iP5 using the CCK adapter so I highly doubt that the DAC is straining the power limits of the MBP USB ports.

    Anyone else notice this kind of behavior or have any other thoughts on what might be going on? Is it possible that the left port on my MBP is defective? I'm doubtful that there's anything wrong with the port given that it powers and transfers data to/from the superdrive just fine which I would think is much more demanding than the DAC.

  2. krick thread starter macrumors regular

    Jun 25, 2009

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