A solution for no audio output on SPDIF when using a B650 (or the like) motherboard. Claude helped me figure out that the dsp device for it was missing and suggested a fix 
Version: FreeBSD 15.1-RELEASE-p6
In Short:
Problem: Missing device to output sound to.
Solution: Set
Checking if you have this device
Version: FreeBSD 15.1-RELEASE-p6
In Short:
Problem: Missing device to output sound to.
Solution: Set
UAUDIO_MAX_CHILD to 3 in /usr/src/sys/dev/sound/usb/uaudio.c and recompile the kernel.
Code:
# diff -u /usr/src/sys/dev/sound/usb/uaudio.c.orig /usr/src/sys/dev/sound/usb/uaudio.c
--- /usr/src/sys/dev/sound/usb/uaudio.c.orig 2026-10-23 05:09:49.176032000 +1000
+++ /usr/src/sys/dev/sound/usb/uaudio.c 2026-10-23 04:44:57.225849000 +1000
@@ -352,7 +352,7 @@
#define UAUDIO_SPDIF_OUT_96K 0x04 /* Out sample rate = 96K */
#define UAUDIO_SPDIF_IN_MIX 0x10 /* Input mix enable */
-#define UAUDIO_MAX_CHILD 2
+#define UAUDIO_MAX_CHILD 3
struct uaudio_softc_child {
device_t pcm_device;Checking if you have this device
Code:
# pciconf -lv | grep -A4 '^hdac'
vendor = 'Advanced Micro Devices, Inc. [AMD/ATI]'
device = 'Navi 48 HDMI/DP Audio Controller'
class = multimedia
subclass = HDA
--
vendor = 'Advanced Micro Devices, Inc. [AMD/ATI]'
device = 'Radeon High Definition Audio Controller'
class = multimedia
subclass = HDA
--
vendor = 'Advanced Micro Devices, Inc. [AMD]'
device = 'Ryzen HD Audio Controller'
class = multimedia
subclass = HDA