IRQ Sharing/Digital Distortion (a.k.a. pops and clicks) with UA-xx or FA-xx on a PC

Tags: distortion,ua-20,ua-25,ua-1000,da-2496,ua-700,ua-1d,fa-101,ua-1x,ua-3,ua-3fx,irq,ua-30
IRQ Sharing is the number one cause of pops and clicks in a Windows-based digital audio workdstation and is most often found with laptop computers, but can be found on desktop computers as well.

In your Windows Device Manager there will be a category labeled 'Universal Serial Bus Controllers.' Within this category, there will be a Host Controller such as 'Intel 82371AB/EB PCI to USB Universal Host Controller.' If this chip shares the same IRQ as any other device, pops and clicks or other digital distortion may occur (often there are more than one device sharing the same IRQ). This same principle can be applied to troubleshooting a FireWire or PCI interface, such as our FA-101 and DA-2496. If the FireWire controller or the DA-PCI card are sharing an IRQ with a different device, the same problem may occur.

To find out whether or not your computer has IRQ sharing in Windows '98/Me, perform the following steps:

1. Click on the "Start" button and select "Settings>" and then "Control Panel" from the list.

2. Double-click the "System" icon and click the "Device Manager" tab at the top.

3. Highlight "Computer" at the top of the list and click properties.

4. Locate your USB Universal Host Controller chip and note the IRQ number to the left.

5. Compare what you see to the above diagram, and note any other devices that share this IRQ.

To find out whether or not your computer has IRQ sharing in Windows 2000/XP, perform the following steps:

1. Click on the "Start" button and select "Settings>" and then "Control Panel" from the list.

2. Double-click the "System" icon and click the "Hardware" tab at the top.

3. Click on the "Device Manager" button.

4. Click on the "View" menu at the top of the screen and choose "Devices by type" from the list.

5. Click on the + next to "Interrupt request (IRQ)" and locate your USB Universal Host controller chip. Note the IRQ number to the left.

6. Compare what you see to the above diagram, and note any other devices that share this IRQ.

If you believe you are experiencing this problem and are on a laptop PC, the best solution is to use a different computer as an audio workstation; one that does not have IRQ sharing. If you're on a laptop or desktop PC, you may purchase a PCMCIA or PCI card, which will, on some computers, use a different IRQ and thus provide a different path for your recorded signal. On occasion, certain motherboards and manufacturers can be contacted for information about IRQ Steering and reserving an IRQ for your USB, FireWire, or PCI card.

Also note that in some cases the solution to IRQ Sharing (other than using a different computer) may be only achieved through disabling other devices on the system, which will reduce the total number of IRQs in use. Even if you do not use a device, it will use an IRQ until it is disabled.