Public bug reported:
Title: Legion 5 15AGP11 (83Q6) - PDM microphone array delivers corrupt
data, not audio (acp-pdm-mach / snd_acp70)
Hardware:
- Lenovo Legion 5 15AGP11, product 83Q6, mainboard LNVNB161216
- CPU: [AMD Ryzen AI 9 465 w/ Radeon 880M
- Released ~July 2026, AMD Ryzen AI 400 series platform (ACP 7.0)
Kernel: 7.0.0-1013-oem (also reproduced on 7.0.0-31-generic)
Sound cards (arecord -l):
card 2: Generic_1 [HD-Audio Generic] - ALC257 Analog
card 3: acppdmmach [acp-pdm-mach] - DMIC capture dmic-hifi-0
Loaded driver chain: snd_acp70 -> snd_acp_pdm / snd_acp_i2s (legacy path,
not SOF - snd_sof_amd_acp70 is loaded but refcount 0, unused)
Problem:
Both capture devices produce no audible output, but the digital mic
array (card 3, acp-pdm-mach) is not simply silent - it delivers
corrupted data. Captured with:
arecord -vv -d 8 -f S16_LE -r 48000 -c 2 vutest.wav
VU meter pegs at MAX throughout, but analysis of the raw samples shows:
- 768000 total samples
- only 17 distinct values across the whole file
- min -32768, max 32767 (full scale)
- stddev only 462.87 despite touching both extremes
- sample pattern is not correlated with speech/silence
This is consistent with a raw PDM bitstream leaking through without
proper decimation/filtering into PCM, rather than a routing, mute,
or gain issue. amixer -c acppdmmach controls returns no mixer
elements at all (no Capture switch, no gain control), consistent
with this being a stub/incomplete machine-driver configuration for
this specific board.
Already ruled out:
- BIOS/UEFI: no mic-disable option present
- Hardware Fn mute key: present, confirmed not muted
- firmware-sof-signed: installed, irrelevant (legacy driver path used, not SOF)
- Tested on both linux-generic and linux-oem-26.04b, same result on both
- ALC257 "Internal Mic" pin (card 2) also silent - not usable as fallback,
likely not physically wired on this board
Suspected cause: DMI machine-quirk table for the ACP 7.0 PDM mach
driver does not yet have an entry for this exact board
(83Q6 / LNVNB161216), so a generic/incorrect topology is applied.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: alsa-base 1.0.25+dfsg-0ubuntu9
ProcVersionSignature: Ubuntu 7.0.0-1013.13-oem 7.0.14
Uname: Linux 7.0.0-1013-oem x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Sep 18 15:10:48 2026
InstallationDate: Installed on 2026-09-03 (15 days ago)
InstallationMedia: Ubuntu 26.04.1 LTS "Resolute Raccoon" - Release amd64
(20260826)
MachineType: LENOVO 83Q6
PackageArchitecture: all
ProcEnviron:
LANG=C.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: alsa-driver
Symptom: audio
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 01/01/2026
dmi.bios.release: 1.28
dmi.bios.vendor: LENOVO
dmi.bios.version: T3CN28WW
dmi.board.asset.tag: NO Asset Tag
dmi.board.name: LNVNB161216
dmi.board.vendor: LENOVO
dmi.board.version: No DPK
dmi.chassis.asset.tag: NO Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Legion 5 15AGP11
dmi.ec.firmware.release: 0.28
dmi.modalias:
dmi:bvnLENOVO:bvrT3CN28WW:bd01/01/2026:br1.28:efr0.28:svnLENOVO:pn83Q6:pvrLegion515AGP11:rvnLENOVO:rnLNVNB161216:rvrNoDPK:cvnLENOVO:ct10:cvrLegion515AGP11:skuLENOVO_MT_83Q6_BU_idea_FM_Legion515AGP11:pfaLegion515AGP11:
dmi.product.family: Legion 5 15AGP11
dmi.product.name: 83Q6
dmi.product.sku: LENOVO_MT_83Q6_BU_idea_FM_Legion 5 15AGP11
dmi.product.version: Legion 5 15AGP11
dmi.sys.vendor: LENOVO
** Affects: alsa-driver (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2167717
Title:
microphone delivers corrupt data
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