Chord QUARTET Upscaler

Quartet – Reference Upscaler for digital high-end audio playback

The Quartet Reference Upscaler is a high-end digital audio device designed for absolute signal purity and marks a technological milestone in digital signal processing for audio. Developed by Chord Electronics, the Quartet combines state-of-the-art FPGA architecture with innovative filtering and conversion technologies to elevate both digital and analog sources to a new reference level.

At its core is the proprietary Blackbird WTA (Watts Transient Aligned) filter technology, which, with approximately four million filter coefficients, enables unprecedented temporal precision in transients. The result is an extremely natural, precise, and spatially stable reproduction that particularly shines with complex musical signals.

Digital reference technology for the highest demands

The Quartet utilizes five Xilinx FPGAs, which together provide exceptional computing power and enable fully hardware-based signal processing. By deliberately avoiding classic FFT convolution in the software, the generation of additional timing errors is minimized and the original signal integrity is preserved.

The implementation achieves a near-ideal mathematical approximation of sinc reconstruction – the gold standard of digital audio conversion – thus ensuring exceptionally precise waveform reconstruction.

Integrated pulse-array ADC for analog sources

A particular highlight is the newly integrated pulse-array ADC, which allows high-quality analog sources such as turntables to be directly incorporated into the upscaling process. Advanced decimation filters minimize aliasing effects and enable reference-level processing – even for classic analog setups.

Dual-housing concept for maximum signal purity

To consistently eliminate electromagnetic interference, the Quartet employs a separate two-box architecture. The sensitive audio stage is powered by an external, highly sophisticated power supply that effectively suppresses mains interference through a special RF filter architecture. The result is a level of sonic purity approaching that of a battery-powered system.

Connectivity and system integration

The Quartet offers extensive connectivity options for modern high-end systems:

• USB-B input (isolated)
• Optical digital input
• BNC inputs and outputs (dual output)
• Supports sampling rates up to 768 kHz
• Optimal integration with reference DACs such as the DAVE DAC

Thanks to its flexible architecture, the Quartet is fully compatible with existing Chord Electronics DAC systems and is designed as a central digital switching point in the high-end setup.

Technical Highlights at a Glance

• Blackbird WTA filter with millions of coefficients for maximum timing precision
• 5× Xilinx FPGA processing with enormous computing power
• Fully hardware-based signal processing without FFT-based software convolution
• Integrated pulse-array ADC for high-quality analog sources
• Dual-enclosure design for complete RF isolation
• 108-bit lossless digital equalizer (±18 dB control range)
• Up to 768 kHz high-resolution signal processing
• Programmable latency (10 ms to 3 s) for perfect AV synchronization

Technical data

Full power consumption: 130 W

Standby power consumption: 20W

Dimensions: 7.8 cm (H) 33.5 cm (W) 15.2 cm (D) (Also applies to the power supply)

Weight: 3 kg; Power supply: 3.2 kg

Digital inputs

2x BNC (or dual BNC)
2x Optical
1x USB-B (galvanically isolated)

Digital outputs

1x optical 192 kHz
1x S/PDIF
2x Dual BNC output with 768 kHz

Analog inputs

2x RCA

Please note: The Choral Ensemble stand shown is sold separately.