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FiiO K9 Pro ESS Desktop DAC and Amplifier
Overview
The FiiO K9 Pro ESS is a desktop DAC and headphone amplifier built around two ESS ES9038PRO DAC chips, one per channel, and two THX AAA 788+ amplifiers, with a linear power supply. It's for listeners who want a serious, fully balanced headphone system on the desk that can also feed active speakers or an amp, and take in wired and Bluetooth sources.
Each ES9038PRO uses all eight of its parallel outputs for one channel, and the signal stays fully differential through the DAC, volume control and amp across a six-stage circuit. The THX AAA 788+ amps deliver 2100mW per channel into 32 ohms and 1100mW into 300 ohms from the 4.4mm and XLR4 balanced outputs, with low, medium and high gain on a physical switch. Power comes from a linear supply with a low-frequency transformer and four 4700µF capacitors, with separate digital and analog power and low-noise LDOs at each stage. Dual femtosecond clocks handle USB and Bluetooth, and volume uses ADC curve reconstruction to keep channels balanced.
Inputs include USB-C on the side, USB-B on the back (up to 384kHz/32-bit and DSD256), coaxial, optical, RCA and 4.4mm balanced line in, and Bluetooth 5.0 through a Qualcomm QCC5124 with LDAC, aptX Adaptive and aptX HD. It works as an MQA renderer with up to 8x unfolding when paired with a compatible player. Outputs are 6.35mm, 4.4mm and XLR4 headphone jacks plus RCA and XLR line outs, and the FiiO Control app connects over Bluetooth Low Energy to adjust filters and channel balance in any input mode. A stand is included for upright use.
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Use the side USB-C port for a phone or laptop you plug in now and then, and the rear USB-B for a permanent computer connection. The balanced outputs are where the K9 Pro ESS really shows its power, delivering 1100mW into 300 ohms versus 281mW from the 6.35mm jack, so high-impedance headphones are best on a 4.4mm or XLR4 cable. For MQA, your player app needs to do the first unfold, since the K9 Pro ESS works as an MQA renderer.
More Info
Why the FiiO K9 Pro ESS Stands Out
Dual ES9038PRO DACs
One chip per channel, all 8 outputs.
Dual THX AAA 788+
2100mW into 32 ohms, 1100mW into 300.
Linear Power Supply
Low-frequency transformer, 4x 4700µF caps.
Fully Balanced Design
Differential from DAC through amp.
Bluetooth 5.0 LDAC
Qualcomm QCC5124 with aptX Adaptive.
Wide Connections
4.4mm/XLR4/6.35mm out, XLR and RCA line.
Buyer's Guide
Who It's For
- The High-Impedance Headphone Owner: Needs 1100mW balanced into 300 ohms.
- The Wired and Wireless Listener: Wants USB, optical and LDAC Bluetooth.
- The Desktop System Builder: Wants XLR and RCA outs for speakers.
How It Compares
Compared with the FiiO K7, the K9 Pro ESS moves from dual AK4493SEQ to dual ES9038PRO DACs and from an external adapter to a built-in linear supply, adds Bluetooth, balanced line inputs and outputs and an XLR4 headphone jack, and doubles balanced power into 300 ohms from 560mW to 1100mW.
FiiO K9 Pro ESS Desktop DAC and Amplifier Specifications
| General Information | |
|---|---|
| Model | FiiO K9 Pro ESS |
| Brand | FiiO |
| Product Type | Desktop DAC and headphone amplifier |
| Colours Available | Black |
| Audio | |
| DAC | ESS ES9038PRO x2 |
| Amplifier | THX AAA 788+ x2 |
| Low-Pass Filter | OPA1612 x2 |
| Volume | NJU72315 x2; ADC curve reconstruction |
| USB / Bluetooth Chips | XMOS XUF208; Qualcomm QCC5124 |
| Gain | Low, medium, high |
| USB | Up to 384kHz/32-bit, DSD256 |
| Coaxial In | Up to 192kHz/24-bit |
| Optical In | Up to 96kHz/24-bit |
| MQA | Renderer, up to 8x unfolding |
| Bluetooth | 5.0 receiver; LDAC, aptX Adaptive, aptX HD, aptX LL, aptX, AAC, SBC |
| Recommended Impedance | 16 to 600Ω |
| 6.35mm Output | |
| Output Power | 2.1W @ 32Ω; 1.1W @ 16Ω; 281mW @ 300Ω |
| SNR | ≥129dB (A-weighted) |
| THD+N | <0.00033% (1kHz, 32Ω) |
| Output Impedance | <1Ω |
| 4.4mm / XLR4 Balanced Output | |
| Output Power | 2.1W @ 32Ω; 1.1W @ 16Ω; 1.1W @ 300Ω |
| SNR | ≥123dB (A-weighted) |
| THD+N | <0.0003% (1kHz, 32Ω) |
| Output Impedance | <1Ω |
| Line Outputs | |
| XLR Balanced | 5Vrms; SNR ≥128dB (A-weighted) |
| RCA | 2.5Vrms; SNR ≥123dB (A-weighted) |
| Connectivity | |
| Inputs | USB-C (side), USB-B, optical, coaxial, RCA line in, 4.4mm balanced line in, Bluetooth |
| Headphone Outputs | 6.35mm, 4.4mm balanced, XLR4 balanced |
| Line Outputs | XLR balanced, RCA |
| App | FiiO Control via Bluetooth Low Energy |
| Physical Specifications | |
| Power Supply | Internal linear; AC 110-115V / 220-230V |
| Dimensions | About 200 x 224.5 x 72mm (excluding feet) |
| Weight | About 2750g |
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