FiiO New K3 Headphone Amplifier

New K3 ESS DAC

Approximate unit weight

Single-ended / balanced outputs

Audio and power connection

A Model-Specific Conversion Architecture

New K3 uses an ES9038Q2M DAC, XMOS XU208 USB decoding, a TI OPA1612 low-pass filter and two OPA926 amplifier chips. This is the newer ESS generation of K3. Check that model identity when comparing older K3 information, since a shared product name does not make their internal hardware identical.

Choose the Correct Headphone Connection

Use the 3.5 mm single-ended headphone jack with a conventional headphone connection, or the 2.5 mm balanced output with a properly wired balanced cable. The connectors are separate output types. Do not assume that changing plug size with a passive adapter converts single-ended headphones into a balanced connection.

Keep Source and Output Roles Clear

USB-C is the audio input and power connection. Optical and coaxial sockets are digital outputs, while the 3.5 mm line output can feed a suitable powered speaker or external amplifier. Those directions matter: the digital output sockets do not accept optical or coaxial source audio.

Formats Matched to Each Input

USB playback supports PCM up to 32-bit/384 kHz and DSD256. The unit provides USB Audio 1.0 and 2.0 operating modes, so the selected mode and computer configuration matter. Use a compatible playback application and the appropriate driver setup when aiming for the higher supported formats.

Set Gain Around Your Headphones

The listed gain settings are Low / High. The control arrangement is ADC analog potentiometer. A separate bass switch changes the low-frequency balance. Start with a low level before connecting or changing headphones, then increase it to suit the recording and headphone sensitivity.

Which version is this?

This listing is New K3 with the ESS ES9038Q2M DAC. Its balanced headphone connector is 2.5 mm, not the 4.4 mm connector used by the larger K11 and K7.

Which headphones should I match it with?

FiiO recommends headphones in the 16–150-ohm range. Sensitivity also matters. The balanced port requires a properly wired 2.5 mm balanced headphone cable; the 3.5 mm port is the single-ended option.

How do the headphone outputs differ?

Use the 3.5 mm single-ended headphone jack with a conventional headphone connection, or the 2.5 mm balanced output with a properly wired balanced cable. The connectors are separate output types. Do not assume that changing plug size with a passive adapter converts single-ended headphones into a balanced connection.

Which way do the source and line connections work?

USB-C is the audio input and power connection. Optical and coaxial sockets are digital outputs, while the 3.5 mm line output can feed a suitable powered speaker or external amplifier. Those directions matter: the digital output sockets do not accept optical or coaxial source audio.

What formats does it support?

USB playback supports PCM up to 32-bit/384 kHz and DSD256. The unit provides USB Audio 1.0 and 2.0 operating modes, so the selected mode and computer configuration matter. Use a compatible playback application and the appropriate driver setup when aiming for the higher supported formats.

Does it need a separate power supply?

New K3 takes DC 5 V / 500 mA power over USB and has no battery. Connect it to a suitable USB source.

Can I use it with passive speakers?

The line output can feed an appropriate external amplifier or powered speakers. Passive speakers need a speaker amplifier; the line output is not a speaker-power connection.