In the Panasonic DP-UB420 4K Blu-ray player owner's manual, you can see a weird audio setting for simulating tube amp sound:
≥ Digital Tube Sound :
This feature gives you a warm sound, like that
produced by a vacuum tube amplifier.
Recommended setting
∫ Sound Effect Frequency
Set the maximum sampling frequency for the
audio selected in “Sound Effects”.
≥ Even when “96/88.2kHz” is selected, an audio
source with a sampling frequency of 96 kHz or
higher will be output with the original sampling
frequency.
≥ When “Sound Effects” is set to “Off”, this setting
is disabled.
∫ DSD Decode Sampling Frequency
Select the settings that suit your sound quality
preferences.
∫ DSD LPF Setting
Select the settings that suit your sound quality
preferences.
∫ Dialog Enhancer*2
The volume of the center channel is raised to
make dialog easier to hear.
∫ High Clarity Sound
Stop processing signals that affect the audio
quality to make the audio quality clearer. ( 31)
Select whether or not to output images.
This setting is able to switch by pressing green
button on the remote control during music
playback.
≥ If “On (Video Off)” is selected, the setting will be
canceled after you play back a video.
*1 Not every function can be set individually.
*2 This function is effective only when “Digital Audio Output” is
set to “PCM” ( 31).
∫ Signal Format
∫ Pop-Out Level
3D position for the Option menu or message
screen, etc. can be adjusted during 3D playback.
Audio Settings
Remaster 1 Pop and rock
Remaster 2 Jazz
Remaster 3 Classical
Digital Tube
Sound 1 A crisp, delicate sound
Digital Tube
Sound 2 A tight, hi-fi sound
Digital Tube
Sound 3 A soft, rich sound
Digital Tube
Sound 4 A clear, powerful sound
Digital Tube
Sound 5
A distinctive mid-range
sound
Digital Tube
Sound 6 A soft, enveloping sound
What do you think of that? Isn't that silly?