Connecting a USB Audio Device


Audio Evolution Mobile's full feature set can be experienced using your device's microphone and speakers (plus, ideally, a pair of headphones if you're planning to record multiple audio tracks) but adding a USB audio interface to this setup opens up the possibility of higher quality recordings and high quality inputs for instruments and superior microphones. Combined with eXtream Software Development's USB audio driver (requires in-app purchase), even higher quality can be achieved as well as lower latency, providing you with everything you need to take your tracks to the next level.  

For more information on eXtream Software Development's USB audio driver, see here.

Requirements


There are three basic rules that determine if your Android/USB audio device combination will work:

  1. Your Android device supports USB host mode
  2. Your USB audio interface is 'USB audio class compliant'.
  3. Your Android device supplies enough power to the USB audio interface or the interface uses an external power source (like a wall-adapter or a powered USB hub)


Your Android device does NOT need to be rooted. Most of the recent Android devices with a USB-C port are compatible. For older devices with a micro-USB port, you need to find out if it supports USB host mode. You can either look in our compatibility list or Google for it. Enter your phone model there in the search field and select your device. Then look at Connectivity and see if it says 'USB host'.

Whether a USB audio interface is 'class compliant' or not is harder to determine. If the device does not require specific drivers under Windows or OSX, then there are good chances it will work. Look in our compatibility list to see if your device is there. If it's not, then you could simply try it out with the free trial version of Audio Evolution Mobile, or in the full version, both with a 45-second limit and a couple of recordings if the USB audio in-app purchase has not been done yet.

NOTE. Please ensure everything is working okay, using either the trial version of Audio Evolution Mobile or the full version if you already own it, before purchasing the eXtream Software Development USB audio driver via in-app purchase.


USB Host OTG Cable

If you have a USB-C connector on your Android device, you will need a converter cable that provides both data and power. If your Android device does not come with one, make sure to buy one that looks like this:


If your Android device features an older micro-USB port, you will need an USB OTG (On-The-Go) cable to trigger the 'USB host' functionality of your Android device. This is the cable you need (when you order a cable, make sure it says 'OTG') :


If your USB audio device is not wall-adapter powered, you may need to supply it with extra power. You can either use a powered USB hub or an OTG-Y cable.This OTG-Y cable is similar to a standard USB OTG cable with a full sized female USB connector on the end that connects to the audio interface, but it branches off into 2 connectors on the other end. One is a standard male micro USB connector for connecting to the android device and the other is a female micro USB connector. The female micro USB connector allows the ability to plug in a standard male micro USB wall charger to inject power into the circuit.

Note: some USB devices require 500mA while some Android wall-adapters only supply 300mA, so using an OTG-Y cable will not help with those and a more powerful adapter or a powered USB hub may be necessary.




Making Connections and Starting the App


So, your Android device has USB Host functionality, you have an OTG cable and a class-compliant USB audio interface? Great.

First, you want to make some connections BEFORE starting Audio Evolution Mobile. Making connections once the app is running can often mean that external devices will not get detected so it's best to go into the habit of connecting everything beforehand. It can also be sensible, for the most reliable recording, to put your device into 'Airplane' mode, shut down as many tasks as possible and disable any battery saving mode. Currently, Audio Evolution Mobile has to run in the foreground, so do not switch to other apps during recording or playback since background apps only get limited CPU time and some Android device halt USB signals.

  1. Plug your OTG cable into your devices USB socket.
  2. Now, use a USB cable to connect your USB audio device to the OTG cables input.
  3. Launch Audio Evolution Mobile.

If, at this point, you get a 'Failed to initialize or open the USB device' message, or similar, it is likely that your device isn't class-compliant and won't work with Android. Please contact us at support@audio-evolution.com if your device doesn't work and we will try to help but unfortunately some devices simply aren't compatible.


If all went well however, the first thing you'll see is this pop-up above. This allows you to select whether you want to use the eXtream Software Development custom USB audio driver (requires in-app purchase to unlock fully) or the inferior Android driver (requires Android 5 or higher). As can be seen, pressing Help will open another pop-up detailing the many benefits offered by eXtream's driver over the Android driver. For more information on the eXtream Software Development USB audio driver, see here.



Next you will get a system message like the one above, allowing you to grant Audio Evolution Mobile access to the USB audio device.



Finally, once access has been granted, you will see the Available devices splash screen (unless you have disabled it in the User Interface section of the Settings). As can be seen above, this device has been successfully connected indicated by the green USB symbol. Since this particular USB device has MIDI connectivity, and the eXtream driver is being used, the USB MIDI device symbol is also green. Click OK and you've successfully launched Audio Evolution Mobile, ready to use the benefits of your USB audio interface.



Settings related to USB audio interfaces

There are various preferences related to USB audio interfaces (when using the eXtream driver) which can be accessed by pressing the Settings button on the Arranger Screen. Then select USB Audio to display the USB audio related options.

Buffer size: we recommend to set it above or equal to 1024 frames. The higher the buffer size, the higher the latency and the lower the CPU usage. Please note that the buffer size displayed here can be roughly compared to that of half the figure on other (desktop) systems. So a buffer size of 1024 frames would roughly equal 512 frames elsewhere (actually even a little less than that). Why you should not go lower than a 1024 frames setting is that it can produce audio artifacts due to buffer under-runs because the driver cannot run in a real-time thread.

Optimize CPU usage: when enabled, will divide USB transfers in such a way that the CPU usage remains low and constant. In case of some multi-channel interfaces, this might prevent the interface from working correctly and you should experiment with this option enabled.

CPU booster: tries to keep the CPU active such that no frequency scaling occurs that would lower the CPU speed.

Always record and playback: some devices like the Digitech RP255 can only function properly when doing simultaneous recording and playback, even if the device only needs to play. Do not enable unless you cannot record or playback.

Bus speed: the app can usually determine the USB speed of the connected interface. In some cases however, this can fail which may for example result in very fast playback speeds. You can try the Full or High speed setting in that case, but in order for the change to have effect, exit the app, disconnect and reconnect the interface and start the app again.


Troubleshooting

If your USB audio interface is not recognized or not working well, we suggest looking at our website for the latest information on compatibility and several troubleshooting tips:

https://www.extreamsd.com/index.php/technology/usb-audio-driver

If that does not help, you are kindly requested to contact support by email at support@audio-evolution.com.