Unknown USB Device (device descriptor Request Failed). KPA to Windows 10 PC

  • I have submitted a ticket to Kemper on this already. In the meantime I wanted to see if anyone could suggest a fix for this.

    The story so far, I've had the KPA power head since 2013. Over the years I have had no issues connecting the KPA to the computer. A few years ago due to health issues I boxed the KPA up and put it in the closet where it sat for three years. I recently started using a newly legalized medication with amazing results. I decided it was time to break out the KPA again and updated everything (os, rm, windows 10, and any hardware you can update on the pc (bios chipset etc.). I had never had the KPA connected to this particular pc as I'd only purchased it within the last year. I connected the KPA to the PC and got the unrecognized device prompt . I looked in device manager and saw the "Unknown USB Device (device descriptor Request Failed)" error on the connection.

    In the following days I have tried 6 different usb a-b cables (5 that were brand new). I have taken my KPA back to OS 1.8, upgraded it to OS 7.3.2 and then to OS 7.4.1. Uninstalled RM 3.0.131 and reinstalled it countless times. I have tried connecting the KPA another PC and it doesn't even recognize that a USB device was plugged in (no sound indications, no popups and nothing in the device manager). I tried connecting the KPA to a laptop and it behaved exactly as the second PC did. I connected the KPA to yet another laptop and got the same unknown usb device error I originally got the my 1st PC. Also both PCs and both laptops had RM 3.0.131 freshly installed on them.

    I've tried using the useless windows Hardware and Devices troubleshooter. I have uninstalled/reinstalled and attempted to update the drivers of every possible usb listing in device manager several times. I disabled the USB Selective Suspend Settings. I've been into the registry to attempt a suggested fix. Nothing has worked. One thing I have noticed is that the unknown usb device error appears when I hook up the USB whether the KPA is powered on or not. Any ideas? 8|


  • I have a similar story:

    The connection between my profiler and Rig Manager on both a Win 10 computer and a Win 7 audio computer built by Sweetwater just stopped one day over two years ago when it was still under warranty. I reinstalled all the updates available at the time on both the profiler and RM. I tried new USB chords but nothing fixed the problem. I got frustrated with it and put it away for a few months. When I started back with it, I finally called Kemper support after going through the same steps as before. The tech said it probably was a windows 10 from win 7 upgrade that caused my computer to stop communicating with Rig Manager. He said if I couldn't get it to working, I could send it in and they would fix it.

    I won't go into what a procrastinator I am, but here we are, 10/18/20. The Kemper Profiler still works like a jewell. Great sounds with the rigs that come in it. It just can't communicate with Rig Manager. The Toast ME editor works fine with the midi to USB adapter by the way.

    Now that I'm determined to get this resolved, I've been researching for the last few days and found a reference to this problem on a Kemper-Cakewalk forum. One poster mentioned that Rig Manager should show up in "Sound, video and game controllers" in Device Manager. It's not there on either of the two computers I've used with the Kemper. I'm pretty sure they used to be there when it was working. I have gone through many of the steps you listed, installing the two newest updates for the profiler and DM. I was just about to start trying to manually install drivers on the Win 10 but I can see from your experience that that probably isn't going to help.

    Worse case, it could be an issue with the Profiler USB type B port on the back of the profiler. I'm probably about to send mine off to British Audio in Nashville, Tenn. Yesterday, a tech there told me that they have replaced the entire circuit board that includes the USB port, but he had never heard of an actual problem with the USB port. They have replaced circuit boards under warranty for other issues and that Kemper just sends them the entire circuit board. It's got to be pretty rare for a USB port to just fail, unless we're putting great stress on the chord or being rough with it. I don't know about you, but mine was on a table and was clear of obstructions and hadn't moved for over a year when it just stopped communicating.

    It could also be a software issue that only a handful of people have had. I've spoken to people at Sweetwater and at Kemper and none of them had heard of this problem. I would love to get mine fixed without having to send it off considering it's now out of warranty. That's my fault. But, as a plus, since Sweetwater pointed me to British Audio ( an official warranty repair center for Kemper), it turns out they have a couple of pretty neat upgrades for Kemper Profilers, so if I have to send it to them, I'm going to get the power amp upgrade.

    Good luck with getting your problem resolved. Kempers' are great by themselves but they're so much better when you have access to Rig Manager and are easier to update.