We’re sorry to see that you’ve experienced undesired audio performance from your computer system, even while using the improved driver that has worked on numerous Windows systems, including my own Windows 7 64-bit Latitude laptop. Can you reproduce this behavior on another computer?

  As you may know, almost every personal computer is a unique hardware and software environment. If one or more variables in the system don’t interact well with the rest of the system, the result can be undesired performance. Thus, we have provided a USB Audio Issues FAQ that describes what configuration variables numerous users have identified as the root cause of their audio issues. http://line6.com/community/docs/DOC-4282

  We strongly suggest that you try all of the suggestions in the FAQ, including BIOS changes and/or a hard drive reformat. As drastic as those procedures may be, they are among the methods that have proven to help many other users correct their system problems. Until you do so, the possibility of your system’s configuration being the root cause of the issue exists.

I had a very similar problem (which was solved)

Symptoms: A periodic loud crackle noise every 3-4 seconds which lasted about 0.5 seconds, highlighted mainly when the guitar port was plugged and was processing an input (i.e being played). However the noise persisted slightly, even with just the background noise, just having the guitar plugged in.

Line6 hardware: Guitar Port

Driver: 4.0.2.3

PC Spec:

Windows 7 SP1 x64

Athlon FX-4100 Zambezi Quad core 3.1MHz

8Gb 1600MHz DDR3 500Gb HDD

Mainboard:

Gigabyte GA-78LMT-S2P

Bios: FDa (beta)

Summary: it turned out to be badly written Mainboard window applications that were causing the high latency on the system... the steps below allowed me to track down the cause and fix the issue.

I had just upgraded my PC from x86 (32 bit) with a new Mainboard and new version of Windows 7. Prior to this i had no issues with the Guitar Port.

Firstly i made sure I was running the PC with the latest drivers. I also let windows update to the latest service pack & auto updates. I was virtually running from a clean install so I figured it had to be a driver or bios issue. But still after installing the latest drivers and updating windows the issue carried on.

I watched the line6 videos about vista/ windows 7 tweaks to optimise the system for audio, which probably would help for a low end system, however in my case (I think) these were not going to help that much. But still applied some of them:

1. disabled my onboard sound - so i just use  the guitar port as my primary sound card
2. disabled any ATA/ IDE port not in use
3. disabled my LAN port as i use a Wi-Fi dongle
4. disabled in the Mainboard Bios any USB options such as Power On from USB, or other USB functions that could interfere with my USB audio device.
5. also disabled anything that i thought wasn't in use on the Mainboard such as Serial ports, power events.

After reading other articles (not just on line6) about crackling and popping I was advised to check the latency, so I found/ downloaded a free app called DPC Latency checker this tests the system for latency issues, which show up in the audio. So I run this app, and as soon as it started testing I could see this same spike in latency I heard through the speakers. After this it was simply a case of trial and error identifying the issue that was causing this high latency spike.

So I then proceeded to remove all programs from windows one at a time until I found the issue.

For me the issue turned out to be badly written Gigabyte Mainboard programs that controlled the USB. Called Power ON/OFF, AutoGreen. And so as I had little faith in any other Gigabyte programs, I uninstalled any other mainboard supplied 'tweak' program.

So for anyone reading this, and if I had to do it all again it would probably be in this order*:



1. Depending on your system, if its bit slow anyway you might be best following the line6 tips on optimising for audio first.
2. Disable in the bios, any USB options that could interfere, such as power on etc. Or anything that could be periodically processing the USB signal on the mainboard.
3. Disable the onboard sound card (if you don't want to do this try it without - or if you need 5.1 etc) but I just saw this as being a waste of resources as the guitar port can do all this as I only need 2.0 out.
4. Open the DPC Latency Checker - as this is the feedback you need to test each change you make.
5. Remove any programs in windows that may be 'tweaking' the system, especially mainboard optimisation programs (check the DPC LC each time you remove).
6. Check devices which may be in conflict with the line6 hardware - LAN, and all other USB devices (check the DPC LC each time you remove). If there is no change in the DPC LC just reinstall the device.
7. Disable in device manager any unused devices (check the DPC LC each time).
8. Start --> Run --> msconfig this will launch the startup services. Uncheck any services & startup processes you can (rinse & repeat checking the DPC LC each time).
9. If after all this its still not working then id proably resort to a format and reinstall windows.

*note: after I managed to reduce the latency spike I noticed certain applications have a latency effect that did interfere with my guitar port. This is Kaspersky and its quite irregular in frequency, but if compounded or you generally have high latency, it might be best either trying different antivirus, alter the settings within it or just disable it while your using the guitar port etc...

hope this helps.