Duet 2 (USB): Troubleshooting

Error on launch of Avid Pro Tools (9 and up)

Symptom: Error on launch of Pro Tools: ”Pro Tools could not initialize the current playback device. Please make sure that the device has been configured correctly.” [381131]

Resolution: This could be an issue with the Current Engine setting in the Pro Tools Playback Engine.

This has been resolved in some scenarios by picking a different Playback Engine:

  • Launch Pro Tools
  • When the splash screen appears on the screen, hold down the “n” key on your keyboard, which will eventually open the Playback Engine dialog for Pro Tools.
  • At the top of this window, you will see the ‘Current Engine’ drop-down menu.
  • Choose a different Engine (such as Pro Tools Aggregate I/O)
  • Click OK.
  • This should allow Pro Tools to launch.

If the solution above fails, you can try deleting the “com.apple.audio.AggregateDevices.plist” preference on Mac OS X. You can find this preference file in the following location:
Macintosh HD > Library > Preferences


Troubleshooting for Duet 2 (USB) not being recognized by Mac

Symptom: Duet not being recognized by the Mac

  1. If you’re using the power supply with Duet, please disconnect.   It is recommended to only connect via USB unless you are prompted to connect the power supply.  This will depend on certain power consumption requirements.
  2. Disconnect the USB cable from the Duet
  3. Download the latest Duet software installer here and run it.
  4. When the software installer asks you to connect a Duet 2, reconnect the USB cable to the Duet while pressing down on the rotary encoder knob.


I’ve connected my studio condenser mic to Duet 2 (USB), but I’m not getting any input. What should I check?

Symptom: Condenser microphone is connected, but there is no signal on the OLED meters of Duet 2 or in my recording software.

Solution: Please be sure you’ve checked the following –

1) Verify that the mic is properly connected to Duet’s input using an XLR cable.

2) Open Apogee Maestro 2 (found in your applications folder), go to the input tab and make sure “Mic” is selected on the channel you’ve connected your microphone to.

3) Check that you’ve selected/engaged 48V phantom power for that input channel.



Can I bypass the preamps in Duet 2 (USB)?

YES!  Duet 2’s preamps can be bypassed if you’d like to connect a line level input source such as an external microphone preamp or mixer.  Here are the two things you’ll need to do:

1) Connect the devices line level output to Duet’s combination input jack using an XLR cable.

2) Go to the input tab in Maestro (found in your Applications folder) and change the input selection from “Mic” or “Inst” to “+4 dBu” or “-10 dBV”.  The line level selectionwill depend on the type of gear you’re connecting.  Professional audio equipment most often uses +4 dBu, while consumer audio gear is set to -10 dBV.

Clicks and Pops on the Mac

Tip – When experiencing clicks and pops on a Mac, try raising the buffer size in the audio app. In
Logic, for example, choose Logic Pro > Preferences > Audio, click the Devices tab, then the Core
Audio tab, and set the I/O Buffer Size to the next highest number.

How do I set my software’s I/O buffer?

The I/O Buffer setting found in most audio software is one of the most crucial, but often ignored, settings in a Mac-based recording system. When choosing a buffer setting, a compromise between the latency through the application and the amount of computer processor power accessible to the application must be made.Latency– the slight delay between the moment you play a note and hear it in your headphones after conversion and processing.

A lower buffer setting results in lower latency but less available processing power. If the application can’t access enough processor power, processor overruns may occur, resulting in audible clicks and pops or error messages that interrupt playback and recording. A higher buffer setting, on the other hand, results in greater amount of accessible processor power (i.e. less chance of overruns) but increases the latency. Determining the best setting requires some trial-and-error in order to find the best compromise.

Keep in mind that as tracks and plug-ins are added to a software session, processor requirements increase. Thus, the buffer setting that works during the early stages of a session might result in processor overruns during later stages. The best strategy is to set the buffer to a lower setting during recording and accept certain limitations on plug-in usage, and then raise the buffer during mixing to utilize the computer’s full processor power when latency isn’t an issue. With the processing power of today’s Macs, you may find that adjustment of the buffer isn’t necessary, and you can leave it at a setting for low latency and still access a sufficient amount of processing power when adding tracks and plug-ins. If you do encounter clicks, pops or software errors, don’t hesitate to experiment with the buffer setting. Please consult the section on Working with GarageBand, Logic and Mainstage to determine how to se the I/O buffer setting is found in your audio application.

When connecting speakers, there is hum and/or buzz at the output.

In most cases, a steady hum or buzz at the output is caused by grounding issues between the Apogee USB interface and the connected equipment. Because bus-powered USB interfaces are grounded through the USB and audio connections, and not through a 3-prong grounded AC connection, the situation may arise where the grounding configuration of the connected equipment must be modified. Check that the computer is grounded with a 3-prong AC connection.

Some experimentation may be required to find the grounding configuration that results in the lowest noise. It may be useful to disconnect all equipment except the Apogee interface, the Mac and a pair of headphones, and then connect additional equipment one piece at a time to determine the source of the grounding issue.

When recording, the input is delayed in my headphones

Decrease the I/O buffer size in your audio application. See “How do I set my software’s I/O buffer?” for more information.