Sound OK using built-in speakers, but loud "static" with headphones

Thu Apr 16 17:31:34 UTC 2015

This is on a fairly new laptop (ref.
<https://wiki.freebsd.org/Laptops/Dell_Precision_M4800>, so there is
some probability that there's an electrical or mechanical issue with the
hardware... but I'd like to eliminate other possibilities before losing
the ability to use the machine for several days.

The static is loud enough that a colleage (whose cube is diagonally
across the aisle from mine at work) heard it (and thought at first
that it was an exceptionally busy disk drive).

At the moment, the laptop is running:

FreeBSD g1-254.catwhisker.org 10.1-STABLE FreeBSD 10.1-STABLE #38  r281579M/281599:1001512: Thu Apr 16 04:27:12 PDT 2015     root at g1-254.catwhisker.org:/common/S1/obj/usr/src/sys/CANARY  i386

(I have recent stable/10 & head for both i386 & amd64 readily
available -- though the head/i386 is a couple of days old: kernels
built both yesterday & today panic early in the boot process,
apparently during hda probes. amd64 doesn't exhibit that.)

/dev/sndstat says:

Installed devices:
pcm0: <NVIDIA (0x0042) (HDMI/DP 8ch)> (play)
pcm1: <NVIDIA (0x0042) (HDMI/DP 8ch)> (play)
pcm2: <Realtek (0x0292) (Analog 2.0+HP/2.0)> (play/rec) default
pcm3: <Realtek (0x0292) (Analog)> (play/rec)

The auto-created devices relevant to the above:

crw-rw-rw-  1 root  wheel  0x9e Apr 16 06:05:04 2015 /dev/dsp0.0
crw-rw-rw-  1 root  wheel  0xa5 Apr 16 06:05:04 2015 /dev/dsp0.1
crw-rw-rw-  1 root  wheel  0x9f Apr 16 06:05:04 2015 /dev/dsp1.0
crw-rw-rw-  1 root  wheel  0xa3 Apr 16 06:05:04 2015 /dev/dsp1.1
crw-rw-rw-  1 root  wheel  0xa2 Apr 16 09:21:58 2015 /dev/dsp2.1
crw-rw-rw-  1 root  wheel  0xa1 Apr 16 06:05:04 2015 /dev/dsp3.0
crw-rw-rw-  1 root  wheel  0xa4 Apr 16 06:05:04 2015 /dev/dsp3.1
crw-rw-rw-  1 root  wheel  0x4c Apr 16 06:01:12 2015 /dev/mixer0
crw-rw-rw-  1 root  wheel  0x4d Apr 16 06:01:12 2015 /dev/mixer1
crw-rw-rw-  1 root  wheel  0x4e Apr 16 06:01:12 2015 /dev/mixer2
crw-rw-rw-  1 root  wheel  0x4f Apr 16 06:01:12 2015 /dev/mixer3
cr--r--r--  1 root  wheel   0x5 Apr 16 06:44:42 2015 /dev/sndstat

Relevant excerpts from dmesg:
...
vgapci0: Boot video device
hdac0: <NVIDIA (0x0e1b) HDA Controller> mem 0xf5080000-0xf5083fff irq 17 at device 0.1 on pci1
xhci0: <Intel Lynx Point USB 3.0 controller> mem 0xf7120000-0xf712ffff irq 16 at device 20.0 on pci0
...
usbus1 on ehci0
hdac1: <Intel Lynx Point HDA Controller> mem 0xf7130000-0xf7133fff irq 22 at device 27.0 on pci0
pcib2: <ACPI PCI-PCI bridge> irq 16 at device 28.0 on pci0
...
load_dn_sched dn_sched WF2Q+ loaded
hdacc0: <NVIDIA (0x0042) HDA CODEC> at cad 0 on hdac0
hdaa0: <NVIDIA (0x0042) Audio Function Group> at nid 1 on hdacc0
pcm0: <NVIDIA (0x0042) (HDMI/DP 8ch)> at nid 5 on hdaa0
pcm1: <NVIDIA (0x0042) (HDMI/DP 8ch)> at nid 7 on hdaa0
hdacc1: <Realtek (0x0292) HDA CODEC> at cad 0 on hdac1
hdaa1: <Realtek (0x0292) Audio Function Group> at nid 1 on hdacc1
pcm2: <Realtek (0x0292) (Analog 2.0+HP/2.0)> at nid 20,21 and 24,25 on hdaa1
pcm3: <Realtek (0x0292) (Analog)> at nid 22 and 18 on hdaa1
usbus1: 480Mbps High Speed USB v2.0
....

Relevant excerpts from output of "pciconf -lv":
...
hdac1 at pci0:0:27:0:      class=0x040300 card=0x05cc1028 chip=0x8c208086 rev=0x04 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Lynx Point High Definition Audio Controller'
    class      = multimedia
    subclass   = HDA
...
hdac0 at pci0:1:0:1:       class=0x040300 card=0x05cc1028 chip=0x0e1b10de rev=0xa1 hdr=0x00
    vendor     = 'NVIDIA Corporation'
    class      = multimedia
    subclass   = HDA
....

The "hw.snd" sysctl OIDs:
g1-254(10.1-S)[14] sysctl hw.snd.|sort
hw.snd.compat_linux_mmap: 0
hw.snd.default_auto: 0
hw.snd.default_unit: 2
hw.snd.feeder_eq_exact_rate: 0
hw.snd.feeder_eq_presets: PEQ:16000,0.2500,62,0.2500:-9,9,1.0:44100,48000,88200,96000,176400,192000
hw.snd.feeder_rate_max: 2016000
hw.snd.feeder_rate_min: 1
hw.snd.feeder_rate_polyphase_max: 183040
hw.snd.feeder_rate_presets: 100:8:0.85 100:36:0.92 100:164:0.97
hw.snd.feeder_rate_quality: 1
hw.snd.feeder_rate_round: 25
hw.snd.latency: 5
hw.snd.latency_profile: 1
hw.snd.maxautovchans: 16
hw.snd.report_soft_formats: 1
hw.snd.report_soft_matrix: 1
hw.snd.verbose: 0
hw.snd.version: 2009061500/i386
hw.snd.vpc_0db: 45
hw.snd.vpc_autoreset: 1
hw.snd.vpc_mixer_bypass: 1
hw.snd.vpc_reset: 0
g1-254(10.1-S)[15] 

Output of "mixer" when the effect is perceived:

g1-254(10.1-S)[23] foreach n ( `jot 4 0` )
foreach? echo "/dev/mixer${n}:"
foreach? mixer -f /dev/mixer$n
foreach? echo ""
foreach? end
/dev/mixer0:
Mixer vol      is currently set to   0:0
Mixer pcm      is currently set to   0:0

/dev/mixer1:
Mixer vol      is currently set to   0:0
Mixer pcm      is currently set to   0:0

/dev/mixer2:
Mixer vol      is currently set to   0:0
Mixer pcm      is currently set to 100:100
Mixer speaker  is currently set to  59:59
Mixer line     is currently set to   1:1
Mixer mic      is currently set to  67:67
Mixer mix      is currently set to  37:37
Mixer rec      is currently set to  37:37
Mixer igain    is currently set to   0:0
Mixer ogain    is currently set to 100:100
Recording source: mic

/dev/mixer3:
Mixer vol      is currently set to   0:0
Mixer pcm      is currently set to   0:0
Mixer rec      is currently set to  37:37
Mixer igain    is currently set to   0:0
Mixer ogain    is currently set to   0:0
Mixer monitor  is currently set to  56:56
Recording source: monitor

g1-254(10.1-S)[28] 

(I had manually set vol & pcm to 0 for mixer0 & mixer1, and set vol
to 0 for mixer2 & mixer3.)

If I set vol to (say) 85 for mixer2 (default), the static remains
the same, but I am able to (also) hear the intended audio.

Using the (internal/system) speakers, sound Just Works as I'm used
to -- but a bit more disruptive at work than I'd prefer for viewing
& listening to an instructional video.

How may I diagnose this?

Thanks!

Peace,
david
-- 
David H. Wolfskill				david at catwhisker.org
Those who murder in the name of God or prophet are blasphemous cowards.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 949 bytes
Desc: not available
URL: <http://lists.freebsd.org/pipermail/freebsd-multimedia/attachments/20150416/d1ae2b33/attachment.sig>