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I've asked four questions now so I'm out of hints. Excuse this question for it's vagueness... Why the hell is my sound card emitting this high pitched squeal when I run it through a mixer with a USB sound card also running through the mixer from the same computer. For reference of past attempts, I've asked four questions trying to get to the bottom of this problem:

  1. Stereo and mono cables and jacks? What happens when you cross them?
  2. What is the difference between a balanced and unbalanced mono jack?
  3. Does a USB Isolator work any different than a powered single-port USB Hub?
  4. Source of ground looping? Different ground for USB and laptop's line out?

I feel like I've learned everything that I need to know about audio equipment and none of it was relevant. I've even updated my BIOS!!! For reference, here are some of the system specs,

BIOS Information
    Vendor: LENOVO
    Version: 6DET71WW (3.21 )
    Release Date: 12/13/2011

System Information
    Manufacturer: LENOVO
    Product Name: 746643U
    Version: ThinkPad X200s

Intel(R) Core(TM)2 Duo CPU     L9600  @ 2.13GHz

Here is the lspci info from the sound card:

00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)

Here is the lsusb info from my USB DAC:

Bus 006 Device 003: ID 08bb:2902 Texas Instruments Japan PCM2902 Audio Codec

Here is what dmesg outputs from the syslog when I plug it in:

new full-speed USB device number 3 using uhci_hcd
New USB device found, idVendor=08bb, idProduct=2902
New USB device strings: Mfr=1, Product=2, SerialNumber=0
Product: USB Audio CODEC 
Manufacturer: Burr-Brown from TI              
input: Burr-Brown from TI               USB Audio CODEC  as /devices/pci0000:00/0000:00:1d.0/usb6/6-2/6-2:1.3/input/input13
hid-generic 0003:08BB:2902.0002: >input,hidraw0: USB HID v1.00 Device [Burr-Brown from TI               USB Audio CODEC ] on usb-0000:00:1d.0-2/input3

I already know the answer to this.. I've spent three days researching the problem and I want this to be out there for others to find.

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  • So - you have one other question on this topic number 4 in your list. Can you answer that one as well, or do you want to merge the questions? (Your other 3 are unconnected to this issue)
    – Rory Alsop ♦
    Commented Nov 1, 2012 at 20:59
  • They're all unconnected, no one who isn't experienced with this problem would have guessed that power regulation for the CPU was interfering with onboard and USB DACs
    – Evan Carroll
    Commented Nov 1, 2012 at 21:17
  • Also, I think #4 is a valuable question even if unrelated. I'd be curious to know the answer. I'll leave it up for bit.
    – Evan Carroll
    Commented Nov 1, 2012 at 21:18
  • Isn't the answer exactly the same though? You have found the cause of the issue. (And it was nothing that I would have expected :-)
    – Rory Alsop ♦
    Commented Nov 1, 2012 at 21:20
  • I'm inclined to wait, I still want to know more about ground. I've read there are numerous ways to make a fake ground but does the ground for audio (3.5mm out) share the same fake ground as USB in?
    – Evan Carroll
    Commented Nov 1, 2012 at 21:35

1 Answer 1

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For some reason Lenovo X200s and X201 have a problem with this. It's probably just specific to the Core 2 chipset:

Intel(R) Core(TM)2 Duo CPU L9600 @ 2.13GHz

BIOS with disabled power management

Anyway, simply disable all power management functionality in the BIOS. It will all cause a draw on something and result in high pitched audio fluctuation. Others with a Core2 have complained about this too.

Lenovo says this about the problem on a different product.:

Due to tolerances, the capacitors in some systems may resonate at high frequencies as the CPU's C-states change. Not all systems will emit these sounds, and due to differences in environment, background noise, and individual user hear acuity, they may not be noticable. This is considered a normal phenomena. Some customers have reported success using ThrottleStop to limit CPU fruquency changes..

Different users report this problem with everything from USB DACs, to USB Headsets -- just about anything audio with USB.

Here are some other computers that are plagued with this problem:

You can find numerious reports of this problem on Tom's Hardware or even on the Intel forums. Many describe this as a whine.

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  • I'd like to point out if Intel wasn't so predisposed obsessing over the environment and other pointless things, my sound would have worked fine.
    – Evan Carroll
    Commented Nov 1, 2012 at 7:10
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    Keep in mind that Intel's 'pointless' obsession with the environment is what keeps your lap from catching fire. Also, in a modern office building, the heat generated by IT gear can put a significant load on the HVAC system, adversely impacting your comfort in the office. (I've had to sign off on six-figure capital expenditures to mitigate the heat generated by the computers required by a smallish A/V editing team!)
    – ObscureRobot
    Commented Nov 1, 2012 at 8:13
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    Great and to think I thought they were in the business of making processors, apparently all they do is design HVAC workarounds and sell them to me as CPUs.
    – Evan Carroll
    Commented Nov 1, 2012 at 8:33
  • it is probably an unvarnished coil resonating and not the cpu at all. Many graphics cards have this same problem under heavier loads.
    – horatio
    Commented Nov 1, 2012 at 14:26
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    Anyway, great find. It's great that you got to the bottom of the problem! ... the very very bottom :)
    – JoshP
    Commented Nov 1, 2012 at 20:14

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