- dmesg output, 2022-01-14
- clock source workaround is present
- `IMPLICIT_FB_GENERIC_DEV(0x1397, 0x0507),` line under playback_implicit_fb_quirks in /sound/usb/implicit.c (doesn't really change the feedback mode as per previous attempt)
- modprobe snd_usb_audio dyndbg==p implicit_fb=1`
- implicit feedback and no stuttering, but had to switch the profiles many times in pavucontrol

[49984.668880] usb 3-3: USB disconnect, device number 22
[50016.322880] usbcore: deregistering interface driver snd-usb-audio
[50020.574773] usbcore: registered new interface driver snd-usb-audio
[50028.188416] usb 3-3: new high-speed USB device number 23 using xhci_hcd
[50028.315600] usb 3-3: config 1 has an invalid interface number: 5 but max is 3
[50028.315614] usb 3-3: config 1 has no interface number 3
[50028.317833] usb 3-3: New USB device found, idVendor=1397, idProduct=0507, bcdDevice= 1.00
[50028.317843] usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[50028.317847] usb 3-3: Product: UMC202HD 192k
[50028.317850] usb 3-3: Manufacturer: BEHRINGER
[50028.317852] usb 3-3: SerialNumber: 12345678
[50028.322197] usb 3-3: 1:1: added playback implicit_fb sync_ep 88, iface 2:1
[50028.322216] usb 3-3: 1:1: add audio endpoint 0x8
[50028.322234] usb 3-3: Creating new data endpoint #8
[50028.322238] usb 3-3: Creating new data endpoint #88
[50028.322398] usb 3-3: 1:1 Set sample rate 192000, clock 40
[50028.327205] usb 3-3: 2:1: add audio endpoint 0x88
[50028.327935] usb 3-3: 2:1 Set sample rate 192000, clock 40
[50028.545091] usb 3-3: [10] FU [PCM Playback Switch] ch = 2, val = 0/1/1
[50028.545114] usb 3-3: [10] FU [PCM Playback Switch] ch = 1, val = 0/1/1
[50028.548309] usb 3-3: [10] FU [PCM Playback Volume] ch = 2, val = -32512/0/256
[50028.551652] usb 3-3: [10] FU [PCM Playback Volume] ch = 1, val = -32512/0/256
[50028.552073] usb 3-3: [11] FU [Mic Capture Switch] ch = 2, val = 0/1/1
[50028.552083] usb 3-3: [11] FU [Mic Capture Switch] ch = 1, val = 0/1/1
[50028.555339] usb 3-3: [11] FU [Mic Capture Volume] ch = 2, val = -32512/0/256
[50028.558568] usb 3-3: [11] FU [Mic Capture Volume] ch = 1, val = -32512/0/256
[50028.710395] usb 3-3: Open EP 0x88, iface=2:1, idx=0
[50028.710407] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=9600, periods=4, implicit_fb=0
[50028.710415] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.710861] usb 3-3: 2:1 Set sample rate 48000, clock 40
[50028.714375] usb 3-3: Setting params for data EP 0x88, pipe 0x41780
[50028.714396] usb 3-3: Set up 12 URBS, ret=0
[50028.714402] usb 3-3: Setting usb interface 2:1 for EP 0x88
[50028.720445] usb 3-3: Closing EP 0x88 (count 1)
[50028.720455] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.720976] usb 3-3: EP 0x88 closed
[50028.722099] usb 3-3: Open EP 0x88, iface=2:1, idx=0
[50028.722108] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=9600, periods=4, implicit_fb=0
[50028.722116] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.722379] usb 3-3: 2:1 Set sample rate 48000, clock 40
[50028.936263] usb 3-3: Setting params for data EP 0x88, pipe 0x41780
[50028.936294] usb 3-3: Set up 12 URBS, ret=0
[50028.936298] usb 3-3: Setting usb interface 2:1 for EP 0x88
[50028.936837] usb 3-3: Closing EP 0x88 (count 1)
[50028.936843] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.937092] usb 3-3: EP 0x88 closed
[50028.937931] usb 3-3: Open EP 0x8, iface=1:1, idx=0
[50028.937937] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=9600, periods=4, implicit_fb=1
[50028.937942] usb 3-3: Open EP 0x88, iface=2:1, idx=0
[50028.937945] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=9600, periods=4, implicit_fb=0
[50028.937949] usb 3-3: Setting usb interface 1:0 for EP 0x8
[50028.938093] usb 3-3: 1:1 Set sample rate 48000, clock 40
[50028.939161] usb 3-3: Setting params for data EP 0x8, pipe 0x41700
[50028.939181] usb 3-3: Set up 12 URBS, ret=0
[50028.939185] usb 3-3: Setting usb interface 1:1 for EP 0x8
[50028.939666] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.939814] usb 3-3: 2:1 Set sample rate 48000, clock 40
[50028.940905] usb 3-3: Setting params for data EP 0x88, pipe 0x41780
[50028.940920] usb 3-3: Set up 12 URBS, ret=0
[50028.940924] usb 3-3: Setting usb interface 2:1 for EP 0x88
[50028.941203] usb 3-3: Starting data EP 0x8 (running 0)
[50028.941208] usb 3-3: No URB submission due to implicit fb sync
[50028.941212] usb 3-3: Starting data EP 0x88 (running 0)
[50028.941317] usb 3-3: 12 URBs submitted for EP 0x88
[50028.943332] usb 3-3: Reopened EP 0x88 (count 1)
[50028.943370] usb 3-3: Closing EP 0x88 (count 2)
[50028.943996] usb 3-3: Reopened EP 0x88 (count 1)
[50028.944018] usb 3-3: Stopping data EP 0x88 (running 1)
[50028.944075] usb 3-3: Stopping data EP 0x8 (running 1)
[50028.945259] usb 3-3: Closing EP 0x8 (count 1)
[50028.945268] usb 3-3: Setting usb interface 1:0 for EP 0x8
[50028.945597] usb 3-3: EP 0x8 closed
[50028.945601] usb 3-3: Closing EP 0x88 (count 2)
[50028.945661] usb 3-3: Closing EP 0x88 (count 1)
[50028.945665] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.945918] usb 3-3: EP 0x88 closed
[50028.959559] usb 3-3: Open EP 0x8, iface=1:1, idx=0
[50028.959567] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=9600, periods=4, implicit_fb=1
[50028.959572] usb 3-3: Open EP 0x88, iface=2:1, idx=0
[50028.959575] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=9600, periods=4, implicit_fb=0
[50028.959579] usb 3-3: Setting usb interface 1:0 for EP 0x8
[50028.959709] usb 3-3: 1:1 Set sample rate 48000, clock 40
[50028.960828] usb 3-3: Setting params for data EP 0x8, pipe 0x41700
[50028.960846] usb 3-3: Set up 12 URBS, ret=0
[50028.960851] usb 3-3: Setting usb interface 1:1 for EP 0x8
[50028.961210] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.961386] usb 3-3: 2:1 Set sample rate 48000, clock 40
[50028.962494] usb 3-3: Setting params for data EP 0x88, pipe 0x41780
[50028.962510] usb 3-3: Set up 12 URBS, ret=0
[50028.962515] usb 3-3: Setting usb interface 2:1 for EP 0x88
[50028.962812] usb 3-3: Starting data EP 0x8 (running 0)
[50028.962821] usb 3-3: No URB submission due to implicit fb sync
[50028.962825] usb 3-3: Starting data EP 0x88 (running 0)
[50028.962926] usb 3-3: 12 URBs submitted for EP 0x88
[50028.963966] usb 3-3: Reopened EP 0x88 (count 1)
[50028.964002] usb 3-3: Closing EP 0x88 (count 2)
[50028.965081] usb 3-3: Reopened EP 0x88 (count 1)
[50028.965121] usb 3-3: Stopping data EP 0x88 (running 1)
[50028.965210] usb 3-3: Stopping data EP 0x8 (running 1)
[50028.967243] usb 3-3: Closing EP 0x8 (count 1)
[50028.967252] usb 3-3: Setting usb interface 1:0 for EP 0x8
[50028.967827] usb 3-3: EP 0x8 closed
[50028.967833] usb 3-3: Closing EP 0x88 (count 2)
[50028.967904] usb 3-3: Closing EP 0x88 (count 1)
[50028.967909] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.968129] usb 3-3: EP 0x88 closed
[50028.977906] usb 3-3: Open EP 0x8, iface=1:1, idx=0
[50028.977932] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=384000, periods=2, implicit_fb=1
[50028.977941] usb 3-3: Open EP 0x88, iface=2:1, idx=0
[50028.977947] usb 3-3:   channels=2, rate=48000, format=S32_LE, period_bytes=384000, periods=2, implicit_fb=0
[50028.977955] usb 3-3: Setting usb interface 1:0 for EP 0x8
[50028.978116] usb 3-3: 1:1 Set sample rate 48000, clock 40
[50028.979233] usb 3-3: Setting params for data EP 0x8, pipe 0x41700
[50028.979250] usb 3-3: Set up 12 URBS, ret=0
[50028.979257] usb 3-3: Setting usb interface 1:1 for EP 0x8
[50028.979630] usb 3-3: Setting usb interface 2:0 for EP 0x88
[50028.979811] usb 3-3: 2:1 Set sample rate 48000, clock 40
[50028.981603] usb 3-3: Setting params for data EP 0x88, pipe 0x41780
[50028.981621] usb 3-3: Set up 12 URBS, ret=0
[50028.981627] usb 3-3: Setting usb interface 2:1 for EP 0x88
[50028.982096] usb 3-3: Starting data EP 0x8 (running 0)
[50028.982104] usb 3-3: No URB submission due to implicit fb sync
[50028.982108] usb 3-3: Starting data EP 0x88 (running 0)
[50028.982202] usb 3-3: 12 URBs submitted for EP 0x88
[50028.984552] usb 3-3: 1:1 Start Playback PCM
[50028.985846] usb 3-3: Reopened EP 0x88 (count 1)
[50028.987265] usb 3-3: Starting data EP 0x88 (running 1)
[50028.987277] usb 3-3: 2:1 Start Capture PCM