Tone Board, re - imagined.
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.
GALLERY
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FEATURES
HEADPHONE
AMPLIFIER
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.
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Volume Knob: Hybrid Digital-to-Analog Volume Control
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Independent Volume Path: Does not affect RCA line-out
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Hardware analog volume for the best possible performance
HIGH
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".
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THD+N: 0.000126% (-118dB)
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SNR: 121dB
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Noise Level: 3.5uVrms
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Crosstalk: >120dB @200K
FULL MQA
DECODING
MQA (Master Quality Authenticated) is an award-winning British technology that delivers the sound of the original master recording. The master MQA file is fully authenticated and is small enough to stream or download.
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XMOS XU216 for full hardware MQA decoding (tri-unfold)
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Listen to hi-res streaming audio and local files
BALANCED
RCA
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.
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Yellow: Ground (Zero)
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Blue: Cold Line (Negative)
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Pink: Hot Line (Positive)
DESIGN
MECHANICAL & THERMAL
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.
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XMOS XU216: Thermally-coupled with the aluminum enclosure
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Volume Knob: Damped with a silicone o-ring and high-viscosity gel
AUDIO ARCHITECTURE
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XMOS XU216: Bit-perfect USB Class 2 audio and full hardware-based MQA decoding
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Intel Altera CPLD: for jitter filtering & pre-shaping
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ESS ES9038Q2M: ESS digital to analog converter chip
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Texas Instruments OPA1612: I/V and LPF stage amplification
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NJU72315: Volume control chip
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RT6863D: Buffer stage amplification
PCB LAYOUT
The motherboard is no larger than a typical credit card, yet contains everything you need from a mini desktop Hi-Fi device.
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6 layers stack-up
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Low dielectric PCB board for smoother audio
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82.0 x 56.0 mm (compatible with VIM series SBCs)
EXPERIENCE
ROTATE - PUSH
ENCODER
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.
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Rotation: Volume Control, Next, Previous
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Double-Push: Mode Selection
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Long Push: Power ON / OFF
LINEAR
POWER SUPPLY
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.
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Connector: USB-C
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Voltage: 5V
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Tone2 Pro will prioritize power from LPS over USB
HI - RES
BLUETOOTH
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.
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USB-C (I2S) port with custom pin-layout
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Khadas-designed external hi-res Bluetooth module
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Compatible codecs: aptX HD, LDAC (Qualcomm QCC5125)
CONVERTERS
& CABLES
Connect your Tone2 Pro to existing balanced XLR-3 equipment, with our converters and cables.
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Balanced RCA to XLR-3 Male Cable (1m)
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Balanced RCA to XLR-3 Male Adapter (0.2m)
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Use standard RCA cables for single-end applications
COUPLE
LISTENING
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.
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Hybrid digital-to-analog encoder for volume control
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Tone2 Pro can drive up to 150 ohm headphones
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Separate amplifiers for each headphone jack
SPECIFICATIONS
[1] Performance testing based on USB input, coaxial input will have slight performance differences.
[2] iPhone support requires the USB-C to Lightning (Apple C78-USBH) cable, normal Lightning charging cables will not work.
