(Probably) hardware related noise

[1984]

Hi

As this is my first post here: Thanks for this great forum. It already helped me a lot without even writing my own posts.

My problem is one that many people seem to have but until now I could not solve it even with the help of some threads here. I have (most probably) hardware related noise coming from my speakers. Especially when I set the CPU governor to performance, watch a movie or move the mouse there is noise.

My audio setup is the following:

• two neusonik speakers each with its own power supply
• a PreSonus Audiobox Usb audio interface with power supply via USB
• Guitar and Keyboard connected to the audio interface
• Keyboard, PC, monitor and speakers are all plugged into the same multi-plug (I hope multi-plug is the right term)
• I use jack with alsa. Jack uses the USB audio interface.
• And finally a PC with the specs seen in this 'lshw' output

Code: Select all

    description: Desktop Computer
    product: To Be Filled By O.E.M. (To Be Filled By O.E.M.)
    vendor: To Be Filled By O.E.M.
    version: To Be Filled By O.E.M.
    serial: To Be Filled By O.E.M.
    width: 64 bits
    capabilities: smbios-2.7 dmi-2.7 vsyscall32
    configuration: boot=normal chassis=desktop family=To Be Filled By O.E.M. sku=To Be Filled By O.E.M. uuid=00020003-0004-0005-0006-000700080009
  *-core
       description: Motherboard
       product: FM2A88M Extreme4+
       vendor: ASRock
       physical id: 0
       serial: E80-3C021400028
     *-firmware
          description: BIOS
          vendor: American Megatrends Inc.
          physical id: 0
          version: P2.00
          date: 01/17/2014
          size: 64KiB
          capacity: 8128KiB
          capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb biosbootspecification uefi
     *-cache:0
          description: L1 cache
          physical id: 9
          slot: L1 CACHE
          size: 192KiB
          capacity: 192KiB
          clock: 1GHz (1.0ns)
          capabilities: pipeline-burst internal write-back unified
     *-cache:1
          description: L2 cache
          physical id: a
          slot: L2 CACHE
          size: 4MiB
          capacity: 4MiB
          clock: 1GHz (1.0ns)
          capabilities: pipeline-burst internal write-back unified
     *-memory
          description: System Memory
          physical id: 15
          slot: System board or motherboard
          size: 8GiB
        *-bank:0
             description: DIMM DDR3 Synchronous 1600 MHz (0,6 ns)
             product: F3-14900CL9-4GBXL
             physical id: 0
             serial: 00000000
             slot: DIMM 0
             size: 4GiB
             width: 64 bits
             clock: 1600MHz (0.6ns)
        *-bank:1
             description: SODIMM DDR3 [empty]
             product: A1_PartNum1
             vendor: A1_Manufacturer1
             physical id: 1
             serial: A1_SerialNum1
             slot: DIMM 1
             width: 64 bits
        *-bank:2
             description: DIMM DDR3 Synchronous 1600 MHz (0,6 ns)
             product: F3-14900CL9-4GBXL
             physical id: 2
             serial: 00000000
             slot: DIMM 0
             size: 4GiB
             width: 64 bits
             clock: 1600MHz (0.6ns)
        *-bank:3
             description: SODIMM DDR3 [empty]
             product: A1_PartNum3
             vendor: A1_Manufacturer3
             physical id: 3
             serial: A1_SerialNum3
             slot: DIMM 1
             width: 64 bits
     *-cpu
          description: CPU
          product: AMD A8-6600K APU with Radeon(tm) HD Graphics
          vendor: Advanced Micro Devices [AMD]
          physical id: 1f
          bus info: cpu@0
          version: AMD A8-6600K APU with Radeon(tm) HD Graphics
          slot: CPUSocket
          size: 3900MHz
          capacity: 3900MHz
          width: 64 bits
          clock: 100MHz
          capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp constant_tsc rep_good nopl nonstop_tsc extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold bmi1 cpufreq
          configuration: cores=4 enabledcores=4 threads=4
     *-pci:0
          description: Host bridge
          product: Family 15h (Models 10h-1fh) Processor Root Complex
          vendor: Advanced Micro Devices, Inc. [AMD]
          physical id: 100
          bus info: pci@0000:00:00.0
          version: 00
          width: 32 bits
          clock: 66MHz
        *-display
             description: VGA compatible controller
             product: Richland [Radeon HD 8570D]
             vendor: Advanced Micro Devices, Inc. [AMD/ATI]
             physical id: 1
             bus info: pci@0000:00:01.0
             version: 00
             width: 32 bits
             clock: 33MHz
             capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
             configuration: driver=fglrx_pci latency=0
             resources: irq:55 memory:d0000000-dfffffff ioport:f000(size=256) memory:ff700000-ff73ffff
        *-multimedia:0
             description: Audio device
             product: Trinity HDMI Audio Controller
             vendor: Advanced Micro Devices, Inc. [AMD/ATI]
             physical id: 1.1
             bus info: pci@0000:00:01.1
             version: 00
             width: 32 bits
             clock: 33MHz
             capabilities: pm pciexpress msi bus_master cap_list
             configuration: driver=snd_hda_intel latency=0
             resources: irq:53 memory:ff744000-ff747fff
        *-usb:0
             description: USB controller
             product: FCH USB XHCI Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 10
             bus info: pci@0000:00:10.0
             version: 09
             width: 64 bits
             clock: 33MHz
             capabilities: pm msi msix pciexpress xhci bus_master cap_list
             configuration: driver=xhci_hcd latency=0
             resources: irq:18 memory:ff74a000-ff74bfff
        *-usb:1
             description: USB controller
             product: FCH USB XHCI Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 10.1
             bus info: pci@0000:00:10.1
             version: 09
             width: 64 bits
             clock: 33MHz
             capabilities: pm msi msix pciexpress xhci bus_master cap_list
             configuration: driver=xhci_hcd latency=0
             resources: irq:17 memory:ff748000-ff749fff
        *-storage
             description: SATA controller
             product: FCH SATA Controller [AHCI mode]
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 11
             bus info: pci@0000:00:11.0
             version: 40
             width: 32 bits
             clock: 66MHz
             capabilities: storage msi ahci_1.0 bus_master cap_list
             configuration: driver=ahci latency=32
             resources: irq:52 ioport:f190(size=8) ioport:f180(size=4) ioport:f170(size=8) ioport:f160(size=4) ioport:f150(size=16) memory:ff751000-ff7517ff
        *-usb:2
             description: USB controller
             product: FCH USB OHCI Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 12
             bus info: pci@0000:00:12.0
             version: 11
             width: 32 bits
             clock: 66MHz
             capabilities: ohci bus_master
             configuration: driver=ohci-pci latency=32
             resources: irq:18 memory:ff750000-ff750fff
        *-usb:3
             description: USB controller
             product: FCH USB EHCI Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 12.2
             bus info: pci@0000:00:12.2
             version: 11
             width: 32 bits
             clock: 66MHz
             capabilities: pm debug ehci bus_master cap_list
             configuration: driver=ehci-pci latency=32
             resources: irq:17 memory:ff74f000-ff74f0ff
        *-usb:4
             description: USB controller
             product: FCH USB OHCI Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 13
             bus info: pci@0000:00:13.0
             version: 11
             width: 32 bits
             clock: 66MHz
             capabilities: ohci bus_master
             configuration: driver=ohci-pci latency=32
             resources: irq:18 memory:ff74e000-ff74efff
        *-usb:5
             description: USB controller
             product: FCH USB EHCI Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 13.2
             bus info: pci@0000:00:13.2
             version: 11
             width: 32 bits
             clock: 66MHz
             capabilities: pm debug ehci bus_master cap_list
             configuration: driver=ehci-pci latency=32
             resources: irq:17 memory:ff74d000-ff74d0ff
        *-serial
             description: SMBus
             product: FCH SMBus Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 14
             bus info: pci@0000:00:14.0
             version: 16
             width: 32 bits
             clock: 66MHz
             configuration: driver=piix4_smbus latency=0
             resources: irq:0
        *-ide
             description: IDE interface
             product: FCH IDE Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 14.1
             bus info: pci@0000:00:14.1
             version: 00
             width: 32 bits
             clock: 66MHz
             capabilities: ide bus_master
             configuration: driver=pata_atiixp latency=32
             resources: irq:17 ioport:1f0(size=8) ioport:3f6 ioport:170(size=8) ioport:376 ioport:f100(size=16)
        *-multimedia:1
             description: Audio device
             product: FCH Azalia Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 14.2
             bus info: pci@0000:00:14.2
             version: 01
             width: 64 bits
             clock: 33MHz
             capabilities: pm bus_master cap_list
             configuration: driver=snd_hda_intel latency=32
             resources: irq:16 memory:ff740000-ff743fff
        *-isa
             description: ISA bridge
             product: FCH LPC Bridge
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 14.3
             bus info: pci@0000:00:14.3
             version: 11
             width: 32 bits
             clock: 66MHz
             capabilities: isa bus_master
             configuration: latency=0
        *-pci:0
             description: PCI bridge
             product: FCH PCI Bridge
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 14.4
             bus info: pci@0000:00:14.4
             version: 40
             width: 32 bits
             clock: 66MHz
             capabilities: pci subtractive_decode bus_master vga_palette
        *-usb:6
             description: USB controller
             product: FCH USB OHCI Controller
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 14.5
             bus info: pci@0000:00:14.5
             version: 11
             width: 32 bits
             clock: 66MHz
             capabilities: ohci bus_master
             configuration: driver=ohci-pci latency=32
             resources: irq:18 memory:ff74c000-ff74cfff
        *-pci:1
             description: PCI bridge
             product: Hudson PCI to PCI bridge (PCIE port 0)
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 15
             bus info: pci@0000:00:15.0
             version: 00
             width: 32 bits
             clock: 33MHz
             capabilities: pci pm pciexpress msi ht normal_decode bus_master cap_list
             configuration: driver=pcieport
             resources: irq:40 memory:ff600000-ff6fffff
           *-network
                description: Wireless interface
                product: AR9485 Wireless Network Adapter
                vendor: Qualcomm Atheros
                physical id: 0
                bus info: pci@0000:02:00.0
                logical name: wlan0
                version: 01
                serial: 10:fe:ed:ce:3a:60
                width: 64 bits
                clock: 33MHz
                capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical wireless
                configuration: broadcast=yes driver=ath9k driverversion=3.11.0-19-lowlatency firmware=N/A ip=192.168.178.42 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn
                resources: irq:16 memory:ff600000-ff67ffff memory:ff680000-ff68ffff
        *-pci:2
             description: PCI bridge
             product: Hudson PCI to PCI bridge (PCIE port 1)
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 15.1
             bus info: pci@0000:00:15.1
             version: 00
             width: 32 bits
             clock: 33MHz
             capabilities: pci pm pciexpress msi ht normal_decode bus_master cap_list
             configuration: driver=pcieport
             resources: irq:41 ioport:e000(size=4096) memory:ff500000-ff5fffff
           *-network
                description: Ethernet interface
                product: QCA8171 Gigabit Ethernet
                vendor: Qualcomm Atheros
                physical id: 0
                bus info: pci@0000:03:00.0
                logical name: eth0
                version: 10
                serial: d0:50:99:00:b1:d7
                capacity: 1Gbit/s
                width: 64 bits
                clock: 33MHz
                capabilities: pm pciexpress msi msix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
                configuration: autonegotiation=on broadcast=yes driver=alx latency=0 link=no multicast=yes port=twisted pair
                resources: irq:54 memory:ff500000-ff53ffff ioport:e000(size=128)
     *-pci:1
          description: Host bridge
          product: Family 15h (Models 10h-1fh) Processor Function 0
          vendor: Advanced Micro Devices, Inc. [AMD]
          physical id: 101
          bus info: pci@0000:00:18.0
          version: 00
          width: 32 bits
          clock: 33MHz
     *-pci:2
          description: Host bridge
          product: Family 15h (Models 10h-1fh) Processor Function 1
          vendor: Advanced Micro Devices, Inc. [AMD]
          physical id: 102
          bus info: pci@0000:00:18.1
          version: 00
          width: 32 bits
          clock: 33MHz
     *-pci:3
          description: Host bridge
          product: Family 15h (Models 10h-1fh) Processor Function 2
          vendor: Advanced Micro Devices, Inc. [AMD]
          physical id: 103
          bus info: pci@0000:00:18.2
          version: 00
          width: 32 bits
          clock: 33MHz
     *-pci:4
          description: Host bridge
          product: Family 15h (Models 10h-1fh) Processor Function 3
          vendor: Advanced Micro Devices, Inc. [AMD]
          physical id: 104
          bus info: pci@0000:00:18.3
          version: 00
          width: 32 bits
          clock: 33MHz
          configuration: driver=k10temp
          resources: irq:0
     *-pci:5
          description: Host bridge
          product: Family 15h (Models 10h-1fh) Processor Function 4
          vendor: Advanced Micro Devices, Inc. [AMD]
          physical id: 105
          bus info: pci@0000:00:18.4
          version: 00
          width: 32 bits
          clock: 33MHz
     *-pci:6
          description: Host bridge
          product: Family 15h (Models 10h-1fh) Processor Function 5
          vendor: Advanced Micro Devices, Inc. [AMD]
          physical id: 106
          bus info: pci@0000:00:18.5
          version: 00
          width: 32 bits
          clock: 33MHz
     *-scsi:0
          physical id: 1
          logical name: scsi3
          capabilities: emulated
        *-disk
             description: ATA Disk
             product: Crucial_CT240M50
             physical id: 0.0.0
             bus info: scsi@3:0.0.0
             logical name: /dev/sda
             version: MU03
             serial: 14080C03C012
             size: 223GiB (240GB)
             capabilities: gpt-1.00 partitioned partitioned:gpt
             configuration: ansiversion=5 guid=cd4f31d9-3ed5-4d57-acbe-c4e42880085b sectorsize=4096
           *-volume:0
                description: Windows FAT volume
                vendor: MSDOS5.0
                physical id: 1
                bus info: scsi@3:0.0.0,1
                logical name: /dev/sda1
                version: FAT32
                serial: e429-4e5c
                size: 95MiB
                capacity: 99MiB
                capabilities: boot fat initialized
                configuration: FATs=2 filesystem=fat name=EFI system partition
           *-volume:1
                description: reserved partition
                vendor: Windows
                physical id: 2
                bus info: scsi@3:0.0.0,2
                logical name: /dev/sda2
                serial: 097a642c-17b6-476a-8e0d-062ab83515d2
                capacity: 127MiB
                capabilities: nofs
                configuration: name=Microsoft reserved partition
           *-volume:2
                description: Windows NTFS volume
                vendor: Windows
                physical id: 3
                bus info: scsi@3:0.0.0,3
                logical name: /dev/sda3
                version: 3.1
                serial: 30c2fca5-bea3-364d-8a20-b472cbd2a1cd
                size: 111GiB
                capacity: 111GiB
                capabilities: ntfs initialized
                configuration: clustersize=4096 created=2014-04-03 19:14:50 filesystem=ntfs name=Basic data partition state=clean
           *-volume:3
                description: EXT4 volume
                vendor: Linux
                physical id: 4
                bus info: scsi@3:0.0.0,4
                logical name: /dev/sda4
                logical name: /
                version: 1.0
                serial: 06154fcb-4155-4a01-b015-d8faefe51ccb
                size: 104GiB
                capabilities: journaled extended_attributes large_files huge_files dir_nlink recover extents ext4 ext2 initialized
                configuration: created=2014-04-05 14:50:22 filesystem=ext4 lastmountpoint=/ modified=2014-04-16 13:14:16 mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,data=ordered mounted=2014-04-16 13:14:16 state=mounted
           *-volume:4
                description: Linux swap volume
                vendor: Linux
                physical id: 5
                bus info: scsi@3:0.0.0,5
                logical name: /dev/sda5
                version: 1
                serial: 8bcabb8c-72e7-4606-ba5b-2e057c484562
                size: 7627MiB
                capacity: 7628MiB
                capabilities: nofs swap initialized
                configuration: filesystem=swap pagesize=4095
     *-scsi:1
          physical id: 2
          bus info: usb@1:3
          logical name: scsi6
          capabilities: emulated scsi-host
          configuration: driver=usb-storage
        *-cdrom
             description: DVD-RAM writer
             product: eSAU208   2
             vendor: Slimtype
             physical id: 0.0.0
             bus info: scsi@6:0.0.0
             logical name: /dev/cdrom
             logical name: /dev/sr0
             version: ML05
             capabilities: removable audio cd-r cd-rw dvd dvd-r dvd-ram
             configuration: status=nodisc
     *-scsi:2
          physical id: 3
          bus info: usb@9:1
          logical name: scsi7
          capabilities: emulated scsi-host
          configuration: driver=usb-storage
        *-disk
             description: SCSI Disk
             product: 2115
             vendor: ASMT
             physical id: 0.0.0
             bus info: scsi@7:0.0.0
             logical name: /dev/sdb
             version: 0
             serial: 2D000000000000000123
             size: 931GiB (1TB)
             capabilities: partitioned partitioned:dos
             configuration: ansiversion=6 sectorsize=4096 signature=00011613
           *-volume
                description: Windows NTFS volume
                physical id: 1
                bus info: scsi@7:0.0.0,1
                logical name: /dev/sdb1
                logical name: /home/chaot/Chaos
                version: 3.1
                serial: 5eca0e19-89e6-f14d-8cce-83387fcfb2a8
                size: 931GiB
                capacity: 931GiB
                capabilities: primary ntfs initialized
                configuration: clustersize=4096 created=2014-04-01 15:51:12 filesystem=ntfs label=Chaos mount.fstype=fuseblk mount.options=rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096 state=mounted

Some things I tried and what effect they had:

• If I plug the PC into another power socket (from another room) the noise is slightly reduced but still exists
• If I exchange the PC with a Laptop with or without battery and also connected to the multi plug and using the USB audio interface there is no noise at all
• The noise stays the same when I disable networking
• The power socket should be grounded but I didn't test it yet
• I have the same noise on Linux and Windows
• I have very quiet (doesn't bother me at all and I think this is normal) and different noise on the phones connected directly to the USB audio interface

This brought me to the conclusion that my PC hardware is the problem. Probably the power supply unit of the PC. As I am a beginner (with regard to digital audio stuff) I didn't want to start exchanging every single part of my PC without even knowing why so I hope that someone could point me in the right direction what I should try first and what tests I could conduct to gather more usefull information about my problem.

Please tell me if there is some information missing in this post that I should supply.

Thanks for reading and I hope someone can help me!

[aprzekaz]

What if you unplug the guitar and keyboard cables from your interface? Is there noise then? If so it could be a cable issue. Maybe move the cables away from your speakers or mouse or invest in some higher quality instrument cables with better shielding. I only say this because I have a similar problem when I move my mouse around next to my cheap instrument cables when they are live.

[1984]

Thanks for your answer!

Right. I also tried changing some things with the cables. My USB audio interface is connected to the following devices:

• PC via USB cable
• 2x speakers via TS 6.3mm
• guitar via TS 6.3mm
• keyboard audio out via TS 6.3mm
• keyboard midi out via midi cable
• phones via TS 3.5mm

Behavior when unplugging things:

• When I unplug everything except USB and speakers the noise doesn't change. It's as loud as before
• Obviously when I unplug the speakers or the USB connection from the audio interface the noise is gone
• Moving the cables such that they don't cross anymore or are as far as possible from each other doesn't have any effect

In my opinion this contradicts the idea that there's something wrong with the cables like suggested from you, aprzekaz. Or am I missing something?

Edit: I forgot to mention that I think it would be strange if there is something wrong with the cables but when using a laptop with the same audio equipment there is no noise at all. I think there should be noise with any PC or laptop if there is a problem with the cables. The layout of the cables almost remained the same when I tried it with a laptop.

[aprzekaz]

Yeah I guess you're right it's not the cables. I'm just shooting in the dark really. Maybe the motherboard in your pc isn't properly grounded or something.

[Shadow_7]

My guess would be motherboard or power supply. You might try using a powered usb hub to de-stress the motherboard a bit, but it probably wont make a difference. I've had cheap electret mics that when placed on my laptops LCD would click when the screen image changed. Like the counter clock on ardour. The only solution to that was to add distance between the input and the computer. Not really a solution though as it still clicked, just less loudly. Balanced cables and external interfaces solves a few woes.

[DepreTux]

I used to have noise on my amps when connected to the wall outlet in my bedroom. I run a ground cable, and noise was softened, but then the computer started inserting noise from mouse movements, fan, and hard drive.

The solution to my problem was to connect the speakers to the grounded outlet and the computer to an ungrounded one.

I hope it helps.

[1984]

Thanks for your answers, again.

Unfortunately right now I don't have the time to try all those things out. But of course I will try them and i'll also report back what I tried and if something changed.

[Shadow_7]

My guess would be power. GPU maxing out the PSU? USB power under spec? Grid power too rough for audio needs? A higher spec'd PSU? A powered USB Hub? A pure sine wave inverter / battery backup system? Just guesses of course.

[bazsound]

disconnecting ground is not wise .

[DepreTux]

disconnecting ground is not wise .

Right, totally. But in my case there are no dell PSUs that are double insulated, and they have a propetary connector, so my only choice would be getting a different brand and soldering the octogonal connector, and I won't break a working PSU (no screws, it's all glued).

Please correct me if I'm making a serious mistake, but I think as long as the amplifiers are grounded, the only risk is the laptop getting shorted, which while possible is not that probable. Don't blame me if you die painfully, though.

Sometimes I'd rather take a chance than abiding static/hum.

On a side note, you could try to eq the noise into a drone note/chord, but that won't work for lots of styles.

One can't always be wise.

[bazsound]

disconnecting ground is not wise .

Right, totally. But in my case there are no dell PSUs that are double insulated, and they have a propetary connector, so my only choice would be getting a different brand and soldering the octogonal connector, and I won't break a working PSU (no screws, it's all glued).

Please correct me if I'm making a serious mistake, but I think as long as the amplifiers are grounded, the only risk is the laptop getting shorted, which while possible is not that probable. Don't blame me if you die painfully, though.

Sometimes I'd rather take a chance than abiding static/hum.

On a side note, you could try to eq the noise into a drone note/chord, but that won't work for lots of styles.

One can't always be wise.

Right so this isnt so series since the ground is disconnected on the laptop side, laptops work on low voltages anyway and everythingin a laptop is insulated and low voltage anyway.

http://en.wikipedia.org/wiki/Ground_loo ... tricity%29

have a look at this page it may not help you solve the issue but its an interesting read and may be usefull.

I think what you done on your laptop is essentially a ground lift which i dont think is really that dangerous,

To the OP do you have stuff connected to different power sources or are they all connected to the 1 outlet on a 4 way?

[headwar]

Hi,

FWIW, I have a similar issue, and it's nearly gone just by unplugging the AC charger from the laptop. So now, when I want to record, I unplug first (beware of cpu throttling by overzealous "energy saving" background programs, though).
You may too have static on your guitar's mics, it worth checking if grounding the strings - just touching them - changes your noise level.
Halogen lamps are known to cause static too, try unplugging any you have nearby. try also to unplug any non necessary AC converter you have around.

My 2cts , regards
Hw

[DepreTux]

I think what you done on your laptop is essentially a ground lift which i dont think is really that dangerous

Yes, the problem is actually a ground loop, since in this country there is rarely an earth wire installed, all the noise of the laptop is shared through the ground cable with the amplifiers, which use the ground cable as a reference for 0V. So all the noise gets amplified, and you hear the mouse moving, the hard drive, the interference from the PSU itself, etc.

The best solution for this is to get a double insulated (class II) power supply for the laptop. Universal laptop chargers tend to be of this kind, look for the square-in-a-square symbol.
This PSUs don't have a ground contact, but they are still safe if the laptop gets shorted. If your setup consists of more than just a laptop and some amps, it's worth checking only the amplifiers are actually grounded, so as to avoid any posible loop.

Another solution for USB cards is to get a USB galvanic isolator (breking the ground loop between the computer and the interface), but those are industrial and expensive.

Lastly, there is a little device hum-x, but I don't know it's means of functioning. It's cheap, but not available in Argentina, so no go for me.

Of all this, the only plausible solution for my laptop was to get an class II PSU, but the connector on the laptop is propetary, and I would have to break the brick to unsolder the cable.


I hope this helps someone.

[1984]

Hi again!

Sorry for not reporting back earlier. At least I have good news.

A few weeks ago I started again trying to reduce the noise. So I changed the power supply which reduced the noise a little but not to a level which would have been acceptable. So then I looked again into the BIOS settings -- which I did several times before -- and I found that I can disable C6 (some scaling algorithm(?) of AMD as far as I know). This greatly reduced the noise! I really don't know why I haven't found this earlier. Because I still had a problem with regular xruns I uninstalled network manager and now manage my wifi connections (yes, I know...) with wpa_supplicant. Now I have hardly any xruns and this reduced the noise again. I also thought that I already tried this, but it seems I haven't.

The noise is still there when I put my speakers on full volume but when reduced to half the volume (which is more than enough for me) I only hear noise when I put an ear a few centimeters away from the speakers.

So thanks for helping, everyone!