Hifiman EF500

gain switch

FiiO KA2

USB-DAC

iFi Audio Zen Can 3

Bass Boost, gain switch

iFi Audio Zen Dac 3

gain switch, USB-DAC, Bass Boost

FiiO BTR17

Microphones, Display, Tone control, USB-DAC, Bluetooth

FiiO KA17

gain switch, USB-DAC

FiiO K17

USB-DAC, Display, USB host, Tone control, gain switch, Wi-Fi, aptX, Infrared, Airplay, Bluetooth

Mackie Hm-800

gain switch

FiiO K11 R2R

USB-DAC, Display, gain switch

Terratec HA-1 batch

Bass Boost, Powerbank

InLine Replacement Tube for AmpUSB HiFi DSD Headphone Tube Amplifier

Mackie Hm-400

FiiO BTR7

Display, Microphones, USB-DAC, Bluetooth

Hifiman Serenade

USB-DAC, Bluetooth

FiiO BTR13

Tone control, Display, USB-DAC, Microphones, Bluetooth