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Pops, clicks, crackles, dropouts, or distortion – USB Audio Troubleshooting Guide
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When using a USB audio interface with your computer, there are a variety of things that can result in pops, clicks, crackles, dropouts, or distortion during playback and recording. This article offers troubleshooting steps and suggestions that should resolve the majority of these problems. 
 

General

System Requirements

Digital audio recording places significant demands on your computer system’s resources.  For the best user experience it is recommended to use a computer system that not only meets, but exceeds the minimum system requirements.  Be sure to check the system requirements for your software as they are likely to be higher than your M-Audio device.


Latest Drivers

Do you have the latest M-Audio device drivers installed for your Operating System?  M-Audio regularly updates its drivers and it is likely that there is a newer driver available than the one included with your device.  The latest driver releases for M-Audio products are available on our drivers/updates page.  If you are unsure of your exact OS version, please see this article.


USB Hubs

Is your M-Audio USB interface connected to a USB port on your keyboard, monitor, or to a multi-port USB hub?  If so, this could be the source of your problem.  Connect the device directly to the computer and test the audio quality.  If the problem persists, continue testing all USB ports.


Hum/Ground Loop/Electrical Noise

If you experience a constant humming or low frequency buzzing you probably have a ground loop.  Try connecting all devices to the same power outlet on the wall.  If you have a laptop, disconnect its power supply to see if the hum/buzz disappears.  Please see this guide for assistance with troubleshooting ground loops.


Digital Synchronization (Clocking)

When recording with the S/PDIF input or output on your M-Audio USB audio interface, synchronization or clocking problems can result in pops, clicks, or distorted audio.  Test recording and playback with the analog inputs/outputs first.  If you experience the same problems, your issue is not with the S/PDIF connection.  If the problem goes away when using the analog I/O, try the following steps to ensure your digital devices are properly synchronized

  • Although standard RCA cables may appear to work for S/PDIF connections, they are not reliable.  Only use 75ohm coaxial cables specifically designed for digital audio
  • When recording to the S/PDIF input of your M-Audio USB Audio interface, you may need to manually set the device for external S/PDIF sync from the M-Audio control panel.  This will synchronize the M-Audio device with your external digital device
    • Make sure the sample rate on your external device matches the sample rate in the M-Audio control panel and your recording software
    • Refer to your device's documentation for information on digital synchronization and clock source selection
  • When playing audio through the M-Audio device's S/PDIF output, your external digital device must be configured to lock or synchronize externally to the clock signal being sent by the M-Audio interface
    • Make sure the sample rate on your external device matches the sample rate in the M-Audio control panel and your recording software


Faulty Cables

Test with a different USB cable; if using a long USB cable, try a shorter cable.  Faulty cables are often times the source of many problems.  Cables with ferrite beads can help reduce noise and interface which can improve stability and audio performance.  Loose connections can result in crackles and interruptions in the audio.  Check the connections of your audio cables to ensure they are secured.    If you hear noise when moving the cables, they may be faulty.  Test with different audio cables.


Below are additional troubleshooting steps specific to Mac and Windows.

 



PC


Buffer Size

Buffers are used to help keep audio hardware and software running smoothly by processing audio in groups of samples rather than one sample at a time. Due to variations between computer hardware and software, it is impossible to recommend a single optimum setting for all systems.  It may be necessary to experiment with various settings until you find the best buffer size for your system.  The goal of setting a buffer size is to reduce it as much as possible without hearing any clicks, pops, or other glitches. If the buffer size is too small, the computer will not be able to make all the required audio calculations in time, and you will hear pops, clicks, and stuttering in your audio streams. On the other hand, if the buffer size is set too high, your computer will process audio without incident, but your software will feel sluggish and unresponsive.

To find your system’s optimum buffer size setting, begin with a high setting and gradually reduce the size until you begin to hear clicks, pops, or other audible glitches in your audio. Then, raise the buffer size setting until these glitches disappear. You may need to stop playing audio any time you change this setting, and certain applications will require you to close the program before making changes, or relaunch the program before the new buffer size settings become active.


CPU Throttling/Power Management Utilities

Many new computer motherboards and processors have varying forms of CPU Throttling and Power Management Utilities that can have a negative effect on any audio playback and recording which will be audible as noise bursts, pops & clicks, or distortion.  Please see the following guide for more information on disabling these utilities to improve performance:

Improve Audio performance by disabling CPU Throttling & Power Mgmt Utilities (PC)

 


IRQ Conflicts

IRQ sharing can also cause these problems.  Follow these steps to check for conflicts:

  1. Go to the device manger (Start>Run>devmgmt.msc)
  2. Select Resources by Connection from the “View” menu
  3. Select Interrupt Request (IRQ) and a list will be displayed
  4. Find your “OHCI Compliant IEEE 1394 Host Controller” in the list
  5. Look for the PCI number listed before your FireWire controller

Do other devices have the same PCI number?  If a device such as the graphics/video card, Network Controller (Ethernet, modem, or wireless), or the built-in audio card have the same number, this may be the source of your problem.  With the exception of your video/graphics cards, these other devices can be disabled to eliminate the conflict.  Right-click and choose disable to disable the device.  To enable the device, right-click and select enable.  If you have installed a FireWire expansion card, shut down the computer and test the card in a different PCI or cardbus slot.  We have a separate article for more in-depth IRQ Troubleshooting.


System Optimization

Audio applications can be affected by system settings and other software and hardware drives installed on your computer. For best possible performance, it is recommended that you optimize your computer system to improve performance with audio applications.  There are a variety of other settings that can be adjusted to improve performance.  See the Optimization sections of these guides, though written for Pro Tools, the optimizations are also applicable to all other audio applications:

 


Additional Troubleshooting

Thesycon’s DPC Latency Checker is a free Windows tool that analyses the capabilities of a computer system to handle real-time data streams properly. It may help to find the cause for interruptions in real-time audio and video streams, also known as drop-outs.  As often times these drouputs are caused by other devices on the system, this tool can be helpful when troubleshooting IRQ’s.  Please visit http://www.thesycon.de/eng/latency_check.shtml for download links and more information on using this tool to check for latency spikes.

If the problem persists, test the device on all USB ports.  You will need to exit your application when moving to a different USB port; Windows should automatically load the drivers to associate them with the device on the new port.  When finished, re-launch your application and test the audio quality.


Windows XP users only; do you experience pops and clicks associated with graphics activity such as opening, closing, or minimizing windows?  Do you get a zipper noise when moving the mouse? Try lowering the Hardware Acceleration for your Video/Graphics Card and see if performance improves.  Click here for a guide to walk you through this process


Windows 7 & Windows Vista users can set the power scheme for high performance an disable USB Selective Suspend as described in this guide.

Windows XP users can disable USB Power Management as described in this guide.


 

 
Mac


Buffer Size

Buffers are used to help keep audio hardware and software running smoothly by processing audio in groups of samples rather than one sample at a time. Due to variations between computer hardware and software, it is impossible to recommend a single optimum setting for all systems.  It may be necessary to experiment with various settings until you find the best buffer size for your system.  The goal of setting a buffer size is to reduce it as much as possible without hearing any clicks, pops, or other glitches. If the buffer size is too small, the computer will not be able to make all the required audio calculations in time, and you will hear pops, clicks, and stuttering in your audio streams. On the other hand, if the buffer size is set too high, your computer will process audio without incident, but your software will feel sluggish and unresponsive.

To find your system’s optimum buffer size setting, begin with a high setting and gradually reduce the size until you begin to hear clicks, pops, or other audible glitches in your audio. Then, raise the buffer size setting until these glitches disappear. You may need to stop playing audio any time you change this setting, and certain applications will require you to relaunch the program before the new buffer size settings become active.

In OS X, this setting is adjusted from within your recording application.  This setting is generally located in the Preferences Menu in an audio configuration menu.  Please refer to your application’s user guide to find out how to change the buffer size. 


System Optimization

Audio applications can be affected by system settings and other software and hardware drives installed on your computer. For best possible performance, it is recommended that you optimize your computer system to improve performance with audio applications.  There are a variety of other settings that can be adjusted to improve performance.  See the Optimization sections of these guides, though written for Pro Tools, the optimizations are also applicable to all other audio applications:


Repair Disk Permissions

This only takes a few minutes and it is a general maintenance routine for the OS, and important to ensure the proper functioning of MIDI and audio.

  1. Open the Utilities folder located in Macintosh HD>Applications >Utilities
  2. Double click to open Disk Utility
  3. Select your Macintosh HD
  4. On the First Aid tab click Repair Disk Permissions

When the permissions repair is complete you can quit the Disk Utility.


Disable Bluetooth and Airport

Bluetooth and Airport Wireless have been known to cause problems with pops, clicks, and distortion during recording and playback.  Disable both of these from System Preferences and then test the audio quality again.  These devices can easily be activated when needed.


Recommended USB Port

MacBook and MacBook Pro users should verify they are connecting their M-Audio USB interface to the recommended USB port.  Specific USB ports on these systems are known to cause pops, clicks, and dropouts in the audio.

MacBook 13.3" recommended USB port

MacBook Pro recommended USB port(s)


Operating System Updates

Is your Operating System up to date?  Since we have seen problems after using the Automatic Software Update to update the OS, we always recommend downloading and installing the “Combo Update”.  Installing the combo update is recommended as a troubleshooting step and ensures that all system files are up to date.  This combo update can be installed on top of your existing OS without having to reformat and lose any files.  For example, if you are using OS X version 10.5.5, go to http://www.apple.com/downloads and search for “10.5.5 combo update”.  Save the appropriate file for your exact OS version to your desktop.  Disconnect your M-Audio USB device before installing the combo update.  Once the combo update is installed repair disk permissions (see above), then uninstall and re-install the latest M-Audio driver and repair disk permissions again.