Khadas Tone2 Pro: Mini Desktop DAC with built-in Headphone Amplifier
Dec 17, 2020 at 3:06 AM Thread Starter Post #1 of 245


Sponsor: KHADAS
Nov 14, 2020
Shenzhen, China
Hi Head-Fiers,

Tone2 Pro is our second generation Tone Board from Khadas that incorporates a variety of user feedback from our first-gen product, the Tone1. ESS ES9038Q2M DAC has been paired with four powerful OPA1612 operational amplifiers, and three buffer amplifiers. This 3-stage amplification pathway enables Tone2 Pro to drive a wide-range of demanding audiophile-grade headphones with impedances of up to 150 ohms.

Other additions to the Tone2 Pro include a 4.4mm balanced headphone jack in addition to the standard 3.5mm single-end jack. The Tone2 Pro's aluminum enclosure incorporates a hybrid digital/analog volume control knob, allowing you to rely entirely on analog signal attenuation for accurate sound reproduction. With not one, but two USB-C ports, you can connect a 5V linear power supply to the second USB-C port whilst having USB-C data on the first for excellent power-noise isolation. Finally we've added an industry-first balanced RCA line-out. These novel RCA ports have three signal-pins instead of two, yet retain the same size and form factor as regular RCA ports.

The latest addition to file format support is MQA decoding. The onboard XMOS XU216 processor enables bit-perfect, hardware-native, USB class II, asynchronous "unfolding" of MQA data for both web streaming and local high fidelity audio playback, enabling future-proof "original master quality" audio reproduction just as the artist intended, but at reasonable file sizes and streaming bandwidth requirements.



Tone2 Pro incorporates a 3-stage amplification system between the DAC and your 3.5mm single-end or 4.4mm balanced headphones. The TI OPA1612 op-amp provides superior audio quality and excellent distortion characteristics.
  • Volume Knob: Hybrid Digital-to-Analog Volume Control
  • Independent Volume Path: Does not affect RCA line-out
  • Hardware analog volume for the best possible performance


Tone2 Pro continues with the time-tested ESS ES9038Q2M DAC chip that is also used in the Tone1. Our community is delighted to know that we've also eliminated the "ESS hump".
  • THD+N: 0.000126% (-118dB)
  • SNR: 121dB
  • Noise Level: 3.5uVrms
  • Crosstalk: >120dB @200K


The XMOS XU216 processor embedded within Tone2 Pro, enables full hardware decoding of MQA files (3 unfolds), so you can listen to hi-res streaming audio or local files, just as the artist intended at "Master Quality".
  • XMOS XU216 processor for full hardware MQA decoding
  • Compatible with hi-res streaming & local playback
  • Tone2 Pro is approved by the MQA Company


Balanced RCA is a new standard pioneered by Khadas that gives you balanced stereo line-out in a standard RCA form-factor. This innovation is covered by a protective-patent.
  • Yellow: Ground (Zero)
  • Blue: Cold Line (Negative)
  • Pink: Hot Line (Positive)
Here explain how we designed the full new Balanced RCA.




Tone2 Pro has a bespoke design that is unique to the DAC world. It's slim aluminum enclosure accommodates many features and requests from our community. For example, a silicone thermal conduction pad moves heat away from the XMOS XU216 processor into the aluminum enclosure, ensuring that bit-perfect audio transmission is unaffected by thermal noise. The hybrid digital-to-analog volume knob is damped with a silicone O-ring and high-viscosity gel, to give you a confident, potentiometer-like feeling every time you need to adjust the volume or change input modes.
  • XMOS XU216: Thermally-coupled with the aluminum enclosure
  • Volume Knob: Damped with a silicone o-ring and high-viscosity gel


  • XMOS XU216: Bit-perfect USB Class 2 audio and full hardware-based MQA decoding
  • Intel Altera CPLD: for jitter filtering & pre-shaping
  • ESS ES9038Q2M: ESS digital to analog converter chip
  • Texas Instruments OPA1612: I/V and LPF stage amplification
  • NJU72315: Volume control chip
  • RT6863D: Buffer stage amplification

The motherboard is no larger than a typical credit card, yet contains everything you need from a mini desktop Hi-Fi device.
  • 6 layers stack-up
  • Low dielectric PCB board for smoother audio
  • 82.0 x 56.0 mm (compatible with VIM series SBCs)




Control your Tone2 Pro's headphone volume and mode selection with the ALPS rotate-push encoder. The RGB ring-light displays real-time visual feedback.
  • Rotation: Volume Control, Next, Previous
  • Double-Push: Mode Selection
  • Long Push: Power ON / OFF
User Manual link.



You can attach a 5V USB-C linear power supply to the second USB-C port, labelled I2S. Some users require clean signal-to-noise ratios when using high-gain amplifiers.
  • Connector: USB-C
  • Voltage: 5V
  • Tone2 Pro will prioritize power from LPS over USB

Attach a Khadas-designed external Bluetooth module to your Tone2 Pro, and stream music wirelessly from your mobile devices. Our module is still in development.
  • USB-C (I2S) port with custom pin-layout
  • Khadas-designed external hi-res Bluetooth module
  • Compatible codecs: aptX HD, LDAC (Qualcomm QCC5125)


Connect your Tone2 Pro to existing balanced XLR-3 equipment, with our male and female converter cables.
  • Balanced RCA to XLR-3 Female Cable (1.0m)
  • Balanced RCA to XLR-3 Male Adapter (0.2m)
  • Use standard RCA cables for single-end applications

Up to two people can listen at once with Tone2 Pro. There are two headphone jacks on the right-side, a 3.5mm single-end and 4.4mm balanced. Listen with those we love.
  • Hybrid digital-to-analog encoder for volume control
  • Tone2 Pro can drive up to 150 ohm headphones
  • Separate amplifiers for each headphone jack



ModelTone2 Pro
OverviewProfessional Hi-Fi DAC & Headphone Amplifier
HighlightsMini desktop DAC with built-in headphone amplifier
World's first balanced RCA line-out
MQA & DSD playback, bit-perfect audio transmission
FinishBlack, Red, Blue
MaterialsEnclosure/Volume Knob: Aircraft-Grade Aluminum
Bottom Cover: ABS, Polycarbonate
Foot Pad: Silicone
DAC Performance [1]Balanced RCA:
THD+N0.000126% (-118dB)
THD+N, A-Weighted0.000112% (-119dB)
Noise, A-Weighted2.75uVrms
DNR, A-Weighted123.5dB
Crosstalk, 200KΩ> 120dB
Output, 200KΩ4.0 Vrms
Frequency Response, 20Hz~20KHz±0.15dB
RCA (Single End):
THD+N0.000158% (-116dB)
THD+N, A-Weighted0.000141% (-117dB)
Noise, A-Weighted1.6uVrms
DNR, A-Weighted122dB
Crosstalk, 100KΩ> 118dB
Output, 100KΩ2.0 Vrms
Frequency Response, 20Hz~20KHz±0.15dB
Headphone Amplifier Performance [1]4.4 Headphone:
Output Impedance2.4Ω
THD+N, 1KHz, 300Ω0.000158% (-116dB)
THD+N, 1KHz, 150Ω0.000158% (-116dB)
THD+N, 1KHz, 32Ω0.000282% (-111dB)
THD+N, 1KHz, 16Ω0.000398% (-108dB)
Noise< 4.2uVrms
Max Output @300Ω83mW (5.0Vrms)
Max Output @150Ω167mW (5.0Vrms)
Max Output @32Ω211mW (2.6Vrms)
Max Output @16Ω123mW (1.4Vrms)
Crosstalk, 32Ω> 117dB
Frequency Response, 20Hz~20KHz±0.15dB
3.5 Headphone:
Output Impedance1.2Ω
THD+N, 1KHz, 150Ω0.000200% (-114dB)
THD+N, 1KHz, 32Ω0.000251% (-112dB)
THD+N, 1KHz, 16Ω0.000316% (-110dB)
Noise< 2.4uVrms
Max Output @150Ω35.3mW (2.3Vrms)
Max Output @32Ω125mW (2.0Vrms)
Max Output @16Ω114mW (1.35Vrms)
Crosstalk, 32Ω> 69dB
Frequency Response, 20Hz~20KHz±0.15dB
Sampling RateUSB Input: PCM 384KHz 32bit [2]
USB Input: DSD 512MHz (Native)
Coaxial Input: 192KHz 24bit
Audio FormatsMQA, AAC, FLAC, APE, WMA, WAV, OGG, MP3 ...
ProcessorXMOS XU216, 16 Real-time Logical Cores
CoprocessorSTM8S003, Programmable
DAC ChipsetESS ES9038Q2M 32-Bit Stereo Mobile Audio DAC
Apple MFiMFi 3.0 [3]
Amplifier ChipsetsI/V Stage: TI OPA1612 x2
LPF Stage: TI OPA1612 x2
Buffer Stage: RT6863D x3
Ultralow Noise LDOs1x ESS ES9311Q, 1.3uVrms (10Hz-100KHz)
5x ADI ADP151, 9uVrms (10Hz-100KHz)
1x ADI ADP7118, 11uVrms (10Hz-100KHz)
1x ADI ADP7182, 18uVrms (10Hz-100KHz)
Jitter Filter TechnologyBuilt-in Intel Altera MAX V CPLD, Pre-shaping Technology
Accusilicon AS318-B Series Professional Audiophile Crystal Oscillator
High Precision0.1% Film Resistors
5% Film Capacitors
PCB BoardStackup: 6 Layers
Glass Transition Temperature (Tg Rating): 170 °C
KnobHybrid Digital Volume Control
Rotate/Push Operation
LEDsSide: White, Pink
Knob: RGB Light Ring
ConnectivityUSB Port: USB-C 2.0
I2S Port: USB-C with I2S Pinout, Linear Power Supply
Balanced RCA (Orange): Coaxial Input
Balanced RCA (White): Left Channel Line-out
Balanced RCA (Red): Right Channel Line-out
4.4 mm Headphone Jack (Balanced)
3.5 mm Headphone Jack (Single End)
O/S CompatibilityWindows 7, 8, 10 (Khadas USB ASIO driver required)
Linux (with UAC2 compliant kernel)
Android (supports OTG function)
Rated VoltageDC 5V
Power ConsumptionPower off: 8mA
Standby: 380mA
DSD256: 450mA (max)
PCM384: 450mA (max)
DSD512: 510mA (max)
PCM768 [2]: 620mA (max)
CompliancesCE, FCC, RoHS
Size17.0mm(h) x 88.0mm(w) x 61.5mm(l) / 68.0mm(with RCA)
Weight100 grams
Warranty1 Year Limited Hardware Warranty
In the BoxTone2 Pro
USB-C Cable (C to C, 1 meter)
Quickstart Guide and Warranty Card

[1] Performance testing based on USB input, coaxial input will have slight performance differences.
[2] PCM 32bit 768kHz support requires a dedicated firmware package with digital volume control disabled.
[3] iPhone support requires the USB-C to Lightning (Apple C78-USBH) cable, normal Lightning charging cables will not work.



You can also visit our website for further information:

Have fun!
Last edited:
Dec 17, 2020 at 11:02 AM Post #2 of 245
Dec 17, 2020 at 11:49 AM Post #4 of 245
Looking forward to this one - love my toneboard and already got a TB2 on the way. Now if I could find the cables for balanced as they aren't listed for sale yet.

Dec 17, 2020 at 12:24 PM Post #6 of 245
Very attractive product and I would definitely consider if I didn't have my current stack.

Im an amp noob but am I missing something? It says 3 stage amplification, can drive demanding cans but output power at 32ohms is 211mW/125mW meanwhile a magni (my current amp) puts out 2.4W at 32 ohms?
Dec 17, 2020 at 1:03 PM Post #8 of 245
Awesome! I'm looking to shrink my desktop footprint and this might be the ticket.
Dec 17, 2020 at 2:00 PM Post #10 of 245
Guys.... Been trying to find out if this dac/amp works like a dongle??
I mean like ibasso DC01 let's say...
Can I connect it via USB C to a dap/smartphone and draw power from the dap/smartphone listening to music at the same time via the same USB C connection?? Is Khadas Tone2 Pro using/drawing power from other compatible devices (daps/smartphones) via USB C connection and transferring data via the same connectivity?? :confused:
Dec 17, 2020 at 2:02 PM Post #11 of 245
Guys.... Been trying to find out if this dac/amp works like a dongle??
I mean like ibasso DC01 let's say...
Can I connect it via USB C to a dap/smartphone and draw power from the dap/smartphone listening to music at the same time via the same USB C connection?? Is Khadas Tone2 Pro using/drawing power from other compatible devices (daps/smartphones) via USB C connection and transferring data via the same connectivity?? :confused:
That seems to be the case, the question would be how much power it needs. Assuming your device can provide enough power then it should work.
Dec 17, 2020 at 2:09 PM Post #12 of 245
That seems to be the case, the question would be how much power it needs. Assuming your device can provide enough power then it should work.
I have searched at the official Khadas forum for an answer but no guarantees yet... Basically if I go on and pre-order Khadas I am going to use it with Hiby R3 or Hiby R5 daps via type c connection
That's why I need to know for sure in advance you see.....
Dec 17, 2020 at 3:20 PM Post #14 of 245
Really nice feature set and $179 with the $20 off coupon. Looks like to be a good deal.

Users who are viewing this thread