Percussa micro super signal processor

MacBook USB port, under scrutiny. Photo: Kevin Hiscott.

Is your MacBook Pro a rightie?

Something’s going on with the one or two left-hand USB ports on all MacBook Pros. I’ve heard some issues with hard disks, and now some problems with audio. (Controllers are evidently just fine.) The solution: use the right-hand USB port for audio instead.

Updated: Reader Adam suggests that this is probably due to a difference in power delivered to the respective ports. USB audio requires more power, and so odds are you’re under-delivering on the left-hand ports. I’m inclined to think that this is exactly what’s going on – unless someone knows something else. (Easy way to test: try plugging in the power adapter. Note that this can be an issue with FireWire, too.)

In fact, even if for some reason M-Audio has found another reason behind this, Andy Ihnatko noted the issue with different USB ports and power variation way back in 2008. It affects non-Pro MacBooks, and I expect likely many PCs, too.

The MacBook. All USB Ports Are Not Equal [Wired Gadget Lab]

M-Audio (now Avid) has gone as far as to tell its customers officially to avoid the use of that port for audio entirely. Native Instruments forum users have evidently had similar discussions. Via matt_bot on Twitter:

The use of USB Audio Devices on the Left-Hand USB Port Is Not Recommended.  This applies to ALL MacBook Pro Models (Core Duo and Core 2 Duo).

•    The 15" MacBook Pro models have 1 USB port on the left side, and one USB port on the right side.
•    The 17" MacBook Pro models have 2 USB ports on the left side, and one USB port on the right side.

Due to the current USB configuration of the 15" MacBook Pro under OS X, use of USB audio devices is supported on the right-hand USB port only.  Use of such devices on the left-hand USB port(s) is not advised because it may cause audio interrupts and/or dropped samples.  However, the use of an iLok on the left-hand port has been qualified and is fully supported.

Due to the current USB configuration of the 17" MacBook Pro under OS X, use of USB audio devices is only supported on the right-hand USB port, and the left-hand USB port farthest from the screen.  Use of such devices on the left-hand USB port closest to the screen is not advised because it may cause audio interrupts and/or dropped samples.  However, the use of an iLok on the left-hand port has been qualified and is fully supported.

These USB port recommendations are specific to USB Audio devices only (such as the FastTrack USB or Audiophile USB).  USB Keyboard and Control Surface products do not have a recommended USB port at this time.

MacBook Pro recommended USB port(s)

That’s got to be a tough technical advisory to issue, like having to tell your users they should turn around in their chair three times counter-clockwise and shout “Mimmymabby” before recording. But I’ve heard indications that devices other than M-Audio’s are seeing symptoms, so I’m inclined to believe there may be something to this.

Now, before you use this to assume this means FireWire is better than USB or PCs are better than Macs or veganism is better for your love life or the end times are upon us, the whole point is what’s causing the issue and why. (Correction: I’m satisfied enough with Adam – and Andy Ihnatko’s – explanation above that I think there’s not much mystery here! So quit with conspiracy folks and trashing vendors you don’t like, folks. Technology doesn’t need superstition; it needs users hungry to know what’s actually going on.)

Of course, that raises a question: why are some USB ports not entirely up to spec on power? My hope would be that USB is USB and you don’t have power variations between ports, but then, I live in a fantasy world of naive hope. (Can anyone comment on PC laptops and power on different ports? I imagine some would have exactly the same issue.)

One theory for the power discrepancy: John von Seggern claims via Twitter that the issue could be the iSight video camera, which does indeed use the USB video bus. (I would think it shouldn’t draw power when switched off, but perhaps that has caused some other change in the configuration.)

Further, we have reports that not only the iSight, but also Bluetooth and other power-consuming peripherals are on the same bus, as well. (That means turning off Bluetooth might be a good idea if you don’t already.) And we have at least one PC with the same issue. This will definitely be something to research with computers, as it’d be pretty desirable to get machines that, erm, don’t do this to their USB ports.

And someone’s having the opposite port work or not work? Now I’m really confused. (I guess we could simplify all of this to say if you’re having problems with USB audio, try either connecting your AC adapter or switching USB ports.)

Amidst all of the USB audio hating, I have to say, it is possible to get good performance out of USB audio interfaces. On the other hand, removing FireWire from MacBooks seems again like a poor choice.