A brief explanation of USB audio problems:
Most USB audio problems are caused by data transfer interrupts on the USB stream that is feeding audio from the driver to the sound card. If there is a software/hardware interaction on your computer that adversely affects that data transfer, the result can be a white noise burst and/or popping and crackling from the audio device. Interrupts can also cause the device to stop functioning, which will require a system reboot for it to work again, but would not fix the problem long-term. USB interrupts generally do not effect most USB devices such as printers, keyboards, mouse, etc., as these devices use a USB bulk mode of transfer and do not produce noticeable problems if data is interrupted.
It should be noted that the complicated interaction of hardware and software on differently configured systems will produce different results, including failure with a small number of computers, regardless of device or manufacturer. The successful use of the USB audio hardware on another computer usually indicates that a problem with the original system needs to be addressed. There is no one-size-fits-all resolution to ensure error-free performance of audio devices on computers, but most USB interrupts can be resolved by one or all of these actions that we have seen help other users:
1. Use the latest Line 6 device drivers. Download them from http://line6.com/software/ or use Line 6 Monkey to update them. Here is an FAQ on how to uninstall the drivers: Uninstalling Line 6 Software and Drivers.
2. Optimize your computer system for audio: See our Knowledge Base items below to learn how:
Also, here is a good tool to use to update your system drivers: http://www.driverupdate.net/.
3. Test all cables to make sure that they are not defective. Use the shortest cable possible. Ensure that they are properly connected.
4. Remove USB hubs from your system: Line 6 does not support the use of USB hubs for any Line 6 product. USB hubs can also cause white noise or audio interrupts. Please disconnect the hub and plug your USB cable directly into a USB port on the back of your computer if you are using a USB hub. Mac users: Make sure you are connecting directly to your computer and not your keyboard, which acts essentially as a USB hub.
5. Adjust the buffer size, sample rate and bit depth in the Line 6 Audio MIDI Control Panel:
PC: Start > control panel> select classic view if you are in category mode > Line 6 Audio and MIDI devices
Mac: Apple > System Preferences > Other > Line 6 Audio and MIDI devices
The driver console will display a Buffer Size slider that you can adjust towards EXTRA SMALL, MEDIUM, or LARGE. Please first move this slider to MEDIUM or LARGE to see if this helps. Your objective is to have little or no latency while eliminating that white noise.
Optionally, adjust the sample rate and bit depth settings to match the project settings in your recording application. For more information on these settings, please see The Line 6 Audio-MIDI Control Panel FAQ.
6. Disable wireless networking devices: On some CPU configurations, actively using wireless networking/connectivity while streaming (recording/playing)computer audio can impact the fidelity of the audio streams (e.g. noise or artifacts are heard in the audio while using wireless connectivity).
7. Change Power Options: Change the Power Options on your computer (PC's only). To change the Power Schemes, go to Start/Settings/Control Panel/Power Options/. Change power schemes to "Always On". Also change all of the Always On Power Scheme settings to "never".
8. Set your Line 6 device as the main sound card on your system: See these Knowledge Base items to learn how:
9. Purchase a PCI based USB card (desktops) or PCMCIA USB card (laptops): These cards often solve the problem of white noise, communication issues and other problems because the USB implementation on these cards overrides the many times less robust USB bus built into your computer. For more information on PCI Cards please visitPCI CARD For more optimization tips, see the following link: Using a Computer with Line 6 Gear
Chipset Error Explanation: If the computer fails to meet standard USB requirements, a possible result the soundcard creates a "white noise burst" at the analog audio outputs. This is caused by a flaw in some USB chipsets that were manufactured by Intel using the ICH6 architecture. The chipsets we have verified as having this problem are the 915G, 915P and 925X chipsets, although others may be affected as well. Intel publishes on their web site an Errata that provides a more detailed explanation. Please note that computers that create this problem produce issues with all USB 1.1 audio interfaces, not just those manufactured by Line 6. For instance, Digidesign provides their customers with similar information on this Intel chipset problem. Also note that your computer may have this problem even if other USB devices seem to behave normally. This is because other USB devices (like USB printers and hard drives) generally use USB's bulk mode of transfer, and do not produce noticeable problems if data is momentarily interrupted, as on these problem Intel chipsets. USB 1.1 audio devices, which have to continually input and output audio data at a fixed sample rate to provide audio, require USB's isochronous transfer mode, which is intended to guarantee the steady flow of data that is required for audio. These Intel chipsets fail to consistently provide the continuous data flow required for the isochronous mode and audio. If you want to know if your chipset is one of the affected ones, go tothis link
and download the program CPU-Z 1.30. This program will gather detailed info on your CPU. Once downloaded, run the program, select the "Mainboard" tab and note the information where it says "Chipset" (e.g. Intel i915PM/GM/GMS Rev 03).
Solution: We do not have a solution that ensures proper performance on these computers. The most successful workaround we have found is adding a PCI based USB card (to desktop computers with these chipsets) or a CardBus or PCMCIA USB controller card (for laptops with these chipsets). Once these cards are installed, these computers often stop exhibiting the "white noise burst" problem, because the USB implementation on these cards overrides the flawed built-in USB implementation of the computers.
Note: ISA motherboards operate at lower bus speeds, and can slow down your computer and can sometimes cause "clicks" in the audio. We recommend using a non-ISA board.
10. Try a Powered USB Hub: Line 6 cannot support the use of powered USB hubs as they can cause connection issues with our server through our software such as Line 6 Monkey or License Manager. Powered hubs can also create connection issues between our devices and our drivers.
However, there have been a few cases where powered hubs actually resolve pops and clicks on certain laptops where the USB ports may not be providing enough power to the Line 6 audio interface. This would typically work with Line 6 audio interfaces that are powered via USB IE: UX1, UX2, KB37.
11. Remove all unused USB drivers: The program USBDeview is a small utility that lists all USB devices that are currently connected to your computer, as well as all USB devices that you previously used. It can be downloaded at http://www.nirsoft.net/utils/usb_devices_view.html.
Advanced Troubleshooting: As stated previously, some hardware/software configurations simply will not work together, so Line 6 cannot guarantee that any of these adjustments will work on any given computer. We have seen these techniques work for other users who are experienced with advanced computer adjustments. Perform these advanced procedures at your own risk. In some cases, the ultimate resolution was to replace the computer.
BIOS Performance Settings: We have seen BIOS settings, especially power management settings such as ACPI, help with audio performance issues. On most Windows computers, you can adjust the BIOS settings by pressing the F10 key as the computer boots up. Check with your PC's documentation for information on how to enter the BIOS settings.
In some BIOS, a setting called "SpeedStep" may be enabled. Similar settings to SpeedStep are "EIST Function" (or “Power Now” or “Cool’n’Quiet”). Speedstep is an Intel efficiency tool that enables the CPU to speed up and slow down according to the load put on it. However it also changes the voltages running through the CPU accordingly and may cause crackles when the CPU steps up and down.
Go into BIOS settings and disable the "SpeedStep" and C1E settings. C1E is the auto voltage setting that is usually enabled along with Speedstep. This should set the CPU to run at its fixed maximum speed with no voltage changes.
Here is a link to a page with further BIOS setting recommendations:
DPC Latency (IRQ hogging): Use Thesycon's DPC Latency Checker (www.thesycon.de/eng/latency_check.shtml) to help detect the possible presence of a hardware device that occasionally takes more than its fair share of interrupt time by displaying latency intervals. Troubleshooting involves disabling hardware one item at a time, then running the Latency Checker each time until the latency subsides in the checker.
Replendence LatencyMon: LatencyMon (http://www.resplendence.com/latencymon) checks if a system is suitable for processing real time audio by measuring DPC and ISR excecution times as well as hard pagefaults. It will provide a comprehensible report and find the kernel modules and processes responsible for causing audio latencies which result in drop outs. It also provides the functionality of an ISR monitor, DPC monitor and a hard pagefault monitor. Note: Be sure to read some of the possible root causes for pops and clicks that the developer of this software offers up under the description of this tool. Some of these advanced tips may help you resolve your issue.
Registry cleaning: Remnants of old installs may bog down system performance.
OS Reinstall: Complete fresh install of your Operating System in the event certain essential OS files or settings have gone bad.
Hard Drive Reformat: Reformat the hard drive to clean out the registry and remove any problem-causing files. Reinstalling the OS and other applications after a reformat of hard drive may repair previously unfixable problems, and may improve system performance.
USB Bus Corruption/Power Issues: Generally, if you have an IRQ problem, increasing buffer sizes should fix it or at least improve it. If the problem has something to do with USB bus corruption, or a problem with power, then increasing the buffer sizes wouldn’t change anything.
It is possible that your USB audio issues are being caused by a corrupt or underpowered USB bus on your computer. We recommend that you consult with a qualified computer technician to verify if this is the case. Be advised that most technicians aren’t properly equipped to deal with such an in-depth technical issue. They may suggest replacing the motherboard, but that may not fix it unless the replacement is a known working model. This is because the problems stem from design issues on the motherboard and will be common to all motherboards of that revision and model. A PCI USB card usually will help before having to go this far.