To check settings

Which sound cards are installed, and what number are they?

> cat /proc/asound/cards
0 [NVidia         ]: HDA-Intel - HDA NVidia
                     HDA NVidia at 0xfc080000 irq 69
1 [Generic        ]: HDA-Intel - HD-Audio Generic
                     HD-Audio Generic at 0xfc500000 irq 72
2 [USB            ]: USB-Audio - Scarlett 2i2 USB
                     Focusrite Scarlett 2i2 USB at usb-0000:30:00.4-2.3, high speed
3 [Pro            ]: USB-Audio - FiiO K5 Pro
                     GuangZhou FiiO Electronics Co.,Ltd FiiO K5 Pro at usb-0000:30:00.4-1, high spee

Focusrite Scarlett 2i2

> cat /proc/asound/card2/stream0 
Focusrite Scarlett 2i2 USB at usb-0000:30:00.4-2.3, high speed : USB Audio

Playback:
  Status: Stop
  Interface 1
    Altset 1
    Format: S32_LE
    Channels: 2
    Endpoint: 0x01 (1 OUT) (SYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 24
    Channel map: FL FR

Capture:
  Status: Running
    Interface = 2
    Altset = 1
    Packet Size = 200
    Momentary freq = 192000 Hz (0x18.0000)
  Interface 2
    Altset 1
    Format: S32_LE
    Channels: 2
    Endpoint: 0x82 (2 IN) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 24
    Channel map: FL FR

UCA202:

# cat /proc/asound/CODEC/pcm0p/sub0/hw_params
# cat /proc/asound/card0/codec#0

access: MMAP_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2 <-------- will be 4 for iO4
rate: 48000 (48000/1) <------ this changes with the input audio file
period_size: 44100
buffer_size: 88200

FiiO

48kHz and below: BLUE

48kHz and above: YELLOW

DSD: GREEN

# cat /proc/asound/card0/stream0 | grep Momentary

or

# cat /proc/asound/card1/stream0 | grep Momentary

   Momentary freq = 44095 Hz (0x5.8308)

- - - -

# cat /proc/asound/card0/stream0 
# cat /proc/asound/card0/pcm0p/sub0/hw_params

GuangZhou FiiO Electronics Co.,Ltd FiiO K5 Pro at usb-0000:00:12.2-3, high spee : USB Audio

Playback:
  Status: Running
    Interface = 1
    Altset = 2
    Packet Size = 36
    Momentary freq = 44095 Hz (0x5.8308)
    Feedback Format = 16.16
  Interface 1
    Altset 1
    Format: S32_LE
    Channels: 2
    Endpoint: 1 OUT (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000, 352800, 384000, 705600, 768000
    Data packet interval: 125 us
  Interface 1
    Altset 2
    Format: S16_LE
    Channels: 2
    Endpoint: 1 OUT (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000, 352800, 384000, 705600, 768000
    Data packet interval: 125 us
  Interface 1
    Altset 3
    Format: SPECIAL
    Channels: 2
    Endpoint: 1 OUT (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000, 352800, 384000, 705600, 768000
    Data packet interval: 125 us

FiiO via S/PDIF

# cat /proc/asound/card1/pcm1p/sub0/hw_params

access: MMAP_INTERLEAVED
format: S32_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 1024
buffer_size: 32768