Chord Electronics Quartet Upscaler

The Chord Electronics Quartet is a reference-class two-box digital upscaler that runs the new Blackbird WTA filter on five Xilinx FPGAs, processing audio with four million filter taps for a tenfold improvement in transient timing accuracy over Chord's previous WTA generation. Eight years in development by Rob Watts, it's purpose-built to unlock the full potential of Chord's flagship DAC, the DAVE.

Key Features of the Chord Electronics Quartet

• Blackbird WTA Filter Architecture: The new Watts Transient Aligned filter delivers at least a tenfold improvement in transient timing accuracy over Chord's previous WTA designs, with nearly 100 percent of filter coefficients reaching the theoretical ideal sinc function.
• Five Xilinx FPGAs: Five times the processing power of the reference DAVE DAC, with 3,700 DSP cores running over two million lines of bespoke code to execute the Blackbird filter without compromise.
• Four Million Filter Taps: Interpolation complexity beyond any standalone DAC, computed directly in hardware rather than via FFT convolution shortcuts that introduce additional timing errors.
• Integrated Pulse Array ADC: A first for a Chord upscaler. Analog sources, including high-end turntables, feed RCA inputs and benefit from the same upscaling and decimation filtering that eliminates aliasing distortion.
• Two-Box Architecture: Audio circuitry isolated from a dedicated Rob-Watts-designed power supply featuring a proprietary pinch-off RF filter architecture, achieving the sonic purity of a battery-powered device from a mains-connected unit.
• 108-bit Lossless Digital EQ: Ten-shelf equalization with plus or minus 18 dB of adjustment across the audio band, with zero degradation of signal quality.
• Programmable Latency: Selectable delay from 10 milliseconds to three seconds for perfect lip-sync during audio-visual playback.
• Comprehensive Isolated Connectivity: Galvanically isolated USB-B, dual BNC (or single BNC) and optical inputs, plus dual BNC outputs at 768 kHz optimized for pairing with the DAVE DAC.

Engineered for the Chord Electronics DAVE DAC

The Quartet is the upscaler the Chord Electronics DAVE has been waiting for. Just as the Hugo M Scaler was developed to extract the full potential of the Hugo TT2, the Quartet exists to do the same for the DAVE, only at a far deeper level. Five Xilinx FPGAs and four million Blackbird WTA filter taps feed the DAVE's dual BNC inputs at 768 kHz, unlocking the maximum digital resolution Chord's flagship DAC was designed to receive. If you own a DAVE, this is the front end it was built for. If you're considering one, the DAVE + Quartet pairing is the reference combination in Chord's lineup.

Eight Years of Development

The Quartet represents the most significant advancement in digital audio technology in Chord Electronics' history. Developed over eight years by Chord's Digital Design Consultant Rob Watts, it addresses a fundamental flaw inherent in standard digital playback: the subtle but critical mistiming of transients that obscures spatial cues, blunts attack, and flattens the realism of recorded music. Every architectural decision in the Quartet exists to correct that flaw at a level no other digital component has approached.

The Blackbird WTA Filter Architecture

At the core of the Quartet's performance is the all-new Blackbird WTA (Watts Transient Aligned) filter. Representing the culmination of 46 years of specialized research, the Blackbird filter uses four million filter taps, the technical measure of interpolation complexity. That figure represents a tenfold increase over previous WTA designs and delivers a corresponding tenfold improvement in transient timing accuracy, while completely eliminating certain transient timing errors that earlier architectures could not.

Technically, nearly 100 percent of the filter's mathematical coefficients reach the theoretical ideal sinc function: the gold standard for perfect waveform reconstruction. All filtering is executed directly within the hardware architecture. By avoiding the software-industry shortcut of FFT convolution, which converts audio to frequency data and back, the Quartet preserves pure signal integrity and delivers unmatched transient fidelity.

Five Xilinx FPGAs and Hardware-Level Processing

To process this complex interpolation algorithm without compromise, the Quartet uses five Xilinx 200T FPGAs, five times the processing power of the reference DAVE DAC. Together they provide 3,700 DSP cores running over two million lines of proprietary code. Every filter calculation is executed in hardware. Nothing is offloaded to a general-purpose processor, nothing is shortcut through frequency-domain conversion. This is what allows the Blackbird filter to operate at full tap depth in real time without introducing latency artifacts that would defeat the purpose of the filter itself.

Integrated Pulse Array ADC for Analog Sources

For the first time in a Chord Electronics upscaler, the Quartet integrates a proprietary Pulse Array ADC. Analog sources, including high-end turntables, connect via RCA inputs and benefit directly from the device's upscaling power. The ADC's advanced decimation filtering eliminates the aliasing distortion that compromises traditional analog-to-digital conversion, outperforming even dedicated studio-grade conversion hardware. For an analog source, the Quartet behaves like the front end of a reference digital chain: take the signal in, eliminate aliasing artifacts, and pass it forward at full Blackbird-grade transient resolution.

Two-Box Architecture and the External Power Supply

The Quartet's two-box configuration isolates sensitive audio circuitry from its power supply. The external PSU is itself a Rob Watts design, incorporating a proprietary pinch-off RF filter architecture, battery-level isolation characteristics, and Chord Electronics' most advanced RF filtering implementation to date. The objective: achieve the exceptional sonic purity of a battery-powered device while running from the mains. Four-stage output isolation further protects the high-rate digital outputs from any noise that could compromise the signal arriving at the DAC.

Lossless EQ and Programmable Latency

The Quartet includes a subjectively lossless 108-bit digital EQ operating at 705.6 / 768 kHz, with ten-band octave control providing plus or minus 18 dB of adjustment. Because the EQ runs at the Quartet's native processing resolution, there is no degradation of signal quality regardless of how aggressively it is used. Programmable latency from 10 milliseconds to three seconds is also included, allowing perfect lip-sync alignment when the Quartet is used in an audio-visual playback chain.

Comprehensive Isolated Connectivity

The rear panel features comprehensive, isolated connectivity. Digital inputs include two BNC (or dual BNC), two optical, and one galvanically isolated USB-B. Digital outputs include one optical at 192 kHz, one S/PDIF, and dual BNC at 768 kHz, capable of unlocking the maximum input resolution of the DAVE DAC. Two RCA analog inputs feed the integrated Pulse Array ADC.

Pair With

The Quartet is part of Chord Electronics' Choral product range, designed to integrate visually and acoustically as a complete reference stack. Pair the Quartet and the DAVE DAC with the Chord Electronics Ultima Pre for reference analog gain, then close out the chain with a Chord Electronics Ultima Integrated for single-chassis power or step up to dedicated Chord Ultima power amplifiers for full reference separates. The Chord Electronics Choral Ensemble Stand pictured with the Quartet is sold separately and provides the proper isolation and visual integration that ties the full Choral chain together.

The Listening Room Difference

We don't just sell high-end audio, we provide a level of service that's as refined as the products we offer. When you invest in a reference upscaler like the Quartet, you deserve more than a box on your doorstep. You deserve a partner who understands the art of sound and is committed to helping you experience it at its absolute best.

Owner Michael Hoatson will personally deliver the Quartet to your home, anywhere in the country. Not a curbside drop-off. Painstaking setup, room placement, full system integration. Third-generation audio family with decades of experience. Bring a system to life.

Chord Electronics Quartet Specifications