Frequency response curve 1
Test conditions: linear input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, single ended output (32Ω load)
Red: left channel; Blue: right channel

Frequency Response Curve 2


Test conditions: linear input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, balanced output (32Ω load)

red: left channel; Blue: right channel

Frequency Response Curve 3


Test conditions: 4.4mm balanced input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, single ended output (32 Ω load)

red: left channel; Blue: right channel

Frequency Response Curve 4


Test conditions: 4.4mm balanced input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, balanced headphone output (32Ω load)

red: left channel; Blue: right channel

Frequency response curve 5


Test conditions: coaxial/optical input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, single ended output (32Ω load)

red: left channel; Blue: right channel

Frequency response curve 6


Test conditions: coaxial/optical input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, balanced headphone output (32Ω load)

red: left channel; Blue: right channel

Frequency Response Curve 7


Test conditions: coaxial/optical input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, single-ended line output (10KΩ load)

red: left channel; Blue: right channel

Frequency Response Curve 8


Test conditions: coaxial/optical input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, balanced line output (10KΩ load)

red: left channel; Blue: right channel

frequency response curve 9


Test conditions: USB DAC/BT input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, single ended output (32Ω load)

red: left channel; Blue: right channel

frequency response curve 10


Test conditions: USB DAC/BT input, -5dB sine signal, high gain, 20Hz-20kHz, balanced headphone output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 1.

Test conditions: linear input, Vin=480mVrms, high gain, single ended output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 9.

Test conditions: USB DAC, playback -3dB sinusoidal signal, high gain, 48kHz 20Hz-20kHz, single ended output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 10.

Test conditions: USB DAC, playback -3dB sinusoidal signal, high gain, 48kHz 20Hz-20kHz, balanced headphone output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 11.

Test conditions: USB DAC, playback -3dB sinusoidal signal, high gain, 48kHz 20Hz-20kHz, single-ended line output (10KΩ load)

red: left channel; Blue: right channel

Distortion diagram of curves 2.

Test conditions: linear input, Vin=480mVrms, high gain, balanced headphone output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 3.

Test conditions: 4.4mm balanced input, Vin=3Vrms, high gain, single ended output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 4.

Test conditions: 4.4mm balanced input, Vin=2.4Vrms, high gain, balanced headphone output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 5.

Test conditions: coaxial/optical input, Vin=480mVrms, high gain, single ended output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 6.

Test conditions: coaxial/optical input, Vin=480mVrms, high gain, balanced headphone output (32Ω load)

red: left channel; Blue: right channel

Distortion diagram of curves 7.

Test conditions: coaxial/optical input, Vin=0.8Vrms, high gain, single-ended line output (10KΩ load)

red: left channel; Blue: right channel

Distortion diagram of curves 8.

Test conditions: coaxial/optical input, Vin=700mVrms, high gain, balanced line output (10KΩ load)

red: left channel; Blue: right channel

frequency response curve 11


Test conditions: USB DAC/BT input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, single-ended line output (10KΩ load)

red: left channel; Blue: right channel

Frequency response curve 12


Test conditions: USB DAC/BT input, -5dB sinusoidal signal, high gain, 20Hz-20kHz, balanced line output (10KΩ load)

red: left channel; Blue: right channel

Distortion diagram of curves 12.

Test conditions: USB DAC, playback -3dB sinusoidal signal, high gain, 48kHz 20Hz-20kHz, balanced line output (10KΩ load)

red: left channel; Blue: right channel

General specifications
Name / Model No. K9 Pro Hardware solution

DAC: AK4499, USB: XMOS XUF208, Bluetooth: QCC5124, LPF: OPA1612 * 2,

volume IC: NJU72315 * 2, AMP: THX AAA788+ * 2, linear transformer
Color Black Volume Scroll Potentiometer+ADC Sampling
Weight ≈2750g Channel balance L12~R12 (0.5dB per level)
Gain L/M/H Bluetooth format indication Supported
FiiO Control Supported Sampling rate indication Supported
Firmware upgrade System firmware and Bluetooth version can be upgraded via USB Deep standby Long press the multi-function button for about 3s
Low battery reminder / Dimensions ≈200×224.5×76mm
Bluetooth transmission / Bluetooth receiver (5.0) AAC/SBC/aptX/aptX LL/aptX HD/LDAC/atpX Adaptive
Bluetooth format indicator SBC: blue, AAC: cyan, aptX HD: yellow, aptX: purple, aptX LL: purple, LDAC: white, atpX Adaptive: green Charging indicator /
Maximum supported sampling rate 384kHz-32bit/DSD256（USB DAC） Recommended headphone impedance 16~600 Ω
192kHz-24bit (coaxial)
96KHz-24bit (optical)
Buttons and interfaces
Button Physical key + toggle switch USB Type-C, USB B (data transmission)
Single-ended line input interface RCA socket Balanced line input interface 4.4mm balanced socket
Spdif in Optical fiber socket Digital coaxial input interface RCA socket
Balanced output interface 4.4mm socket, XLR4 balanced socket Headphone output interface Standard 6.35 mm socket
Balanced line output interface XLR3 balanced socket Single-ended line output interface RCA socket
Power parameters
Power supply AC 110-115V~/AC 220-230V~ （Recommended） Battery capacity /
Charging time / PO battery life /
Audio parameters
Single-ended line output performance parameters
THD+N ＜0.0007%(1kHz/10kΩ/dbA) SNR ≥123dB (dbA)
Crosstalk ≥110dB (1kHz/10kΩ) Noise floor ＜1.9μV（dbA）
Frequency response 20Hz~20kHz (-3dB) Line Level 2.5Vrms (1kHz/10kΩ)
Balanced line output performance parameters
THD+N ＜0.0004%(1kHz/10kΩ/dbA) SNR ≥128dB (dbA)
Crosstalk ≥123dB (1kHz/10kΩ) Noise floor ＜1.9μV（dbA）
Frequency response 20Hz~20kHz (-3dB) Line Level 5Vrms (1kHz/10kΩ)
Single-ended headphone output performance parameters（6.35mm）
Continuous undistorted output power 1 ≥1.1W（16Ω / THD+N＜1%， AUX IN) Output impedance ＜1Ω（32Ω）
Continuous undistorted output power 2 ≥2W（32Ω /THD+N＜1%，AUX IN) Crosstalk ≥75dB (1 kHz/32Ω，AUX IN)
Continuous undistorted output power 3 ≥278mW（300Ω / THD+N＜1%，AUX IN) THD+N ＜0.0005% (1 kHz/32Ω/dbA)
Noise floor ＜2μV（dbA） SNR ≥123dB (dbA)
Frequency response 20 Hz~20kHz (-3dB) MAX Output Voltage ＞26Vp-p
Balanced headphone output performance parameters（4.4mm/XLR4）
Continuous undistorted output power 1 ≥1.1W（16Ω / THD+N＜1%，AUX IN) Output impedance ＜1Ω（32Ω）
Continuous undistorted output power 2 ≥2W（32Ω /THD+N＜1%，AUX IN) Crosstalk ≥114dB (1 kHz，AUX IN)
Continuous undistorted output power 3 ≥1.1W（300Ω / THD+N＜1%，AUX IN) THD+N ＜0.0004% (1 kHz/32Ω/dbA)
Noise floor ＜3μV（dbA） SNR ≥123dB (dbA)
Frequency response 5Hz~50kHz (-3dB) MAX Output Voltage ＞51Vp-p