Re: [BUG] snd-usb-audio: Audient iD14 (2708:0008) 20 dB channel imbalance

On Tue, 11 Aug 2026 20:13:45 +0200,
Neil Andrews wrote:
> 
> On Tue, 11 Aug 2026, Takashi Iwai wrote:
> > It's fine to skip the volume if it actually improves -- so please test
> > it ;)
> >
> > Judging from your description, an alternative with keeping the volume
> > control would be to just rename it; the problem is that it's tied with
> > "Speaker".  You can name it a different, some non-standard one,
> > instead, too.
> 
> Hi Takashi,
> 
> I tested both on 7.1.6 with sound/usb rebuilt out of tree, measured with
> the loopback rig from the original report. Both fix it. I would suggest
> the rename.
> 
> Baseline, unpatched, PipeWire at 50% (control driven to 109/127):
> 18.00 dB imbalance.
> 
> 1. { 12, NULL }
> 
> Control gone, userspace falls back to software volume, 0.00 dB. So it
> does improve.
> 
> One wrinkle: FU 12 keeps its value across a module reload, so if the
> quirk arrives while the hardware is already attenuated, the imbalance
> stays and there is no longer a control with which to undo it (measured:
> 18.00 dB, control absent). Only a power cycle clears it, which matters
> for anyone whose saved ALSA state holds a value below 0 dB.
> 
> 2. { 12, "Monitor Mix Playback" }
> 
> --- a/sound/usb/mixer_maps.c
> +++ b/sound/usb/mixer_maps.c
> @@ -495,6 +495,19 @@
>  	{}
>  };
> 
> +/* Audient iD14: FU 12 advertises Volume on only 4 of its 6 logical channels
> + * and sits on the monitor-mixer branch, but it is traced through to the
> + * Speaker output terminal and gets named "Speaker Playback Volume". Userspace
> + * then adopts it as the stream's hardware volume, and any setting below 0 dB
> + * attenuates some channels but not others (20 dB imbalance at 80%). Give it a
> + * non-standard name so that it is no longer taken for the stream's master
> + * volume, while remaining reachable for anyone who wants the monitor gain.
> + */
> +static const struct usbmix_name_map audient_id14_map[] = {
> +	{ 12, "Monitor Mix Playback" },	/* FU, partial coverage */
> +	{}
> +};
> +
>  /*
>   * Control map entries
>   */
> @@ -579,6 +592,11 @@
>  		.map = maya44_map,
>  	},
>  	{
> +		/* Audient iD14 */
> +		.id = USB_ID(0x2708, 0x0008),
> +		.map = audient_id14_map,
> +	},
> +	{
>  		/* KEF X300A */
>  		.id = USB_ID(0x27ac, 0x1000),
>  		.map = scms_usb3318_map,
> 
> Gives numid=11,name='Monitor Mix Playback Volume'. PipeWire no longer
> picks it up (control stays at 127, 0.00 dB), and it still works when set
> deliberately, so an attenuated device can be recovered: 107 by hand
> gives 20.00 dB, back to 127 gives 0.00 dB. The name ends in "Playback"
> because a mapped name suppresses the automatic " Playback" but still
> gets " Volume" appended.
> 
> 3. A qualification to my report
> 
> I said userspace adopts the control as the card's hardware playback
> volume, without qualifying it. That is too broad.
> 
> alsa-ucm-conf 1.2.16.1 ships
> USB-Audio/Audient/Audient-iD14-HiFi-0008.conf, which splits the device
> into 2-channel sinks and declares no playback mixer element. With it in
> use PipeWire never touches FU 12: the control stays at 127 at every
> volume setting, on both split sinks and on the underlying node.
> Reproducing needs the ACP path instead, which I got by setting
> api.alsa.use-ucm = false for the device in WirePlumber (then 100% ->
> 127, 80% -> 122, 50% -> 109). All measurements above were taken that
> way.
> 
> So the affected set is narrower than I implied: the ACP path rather than
> that UCM profile, plus anyone whose saved ALSA state carries a value
> below 0 dB, since that is restored at boot either way. The descriptor
> problem itself is unchanged.
> 
> Happy to send either version as a proper patch with a Signed-off-by, and
> to test anything else on the hardware.

Let's take the rename approach, then.  Dropping can be done anytime
later if really needed, too.  Please submit a formal patch.


thanks,

Takashi