From M Scaler to Quartet: A New Kind of Digital Audio Upscaler
Chord Electronics’ new Quartet upscaler is being positioned as a landmark digital audio upscaler in the company’s 37‑year history. Designed by long‑time digital specialist Rob Watts, Quartet focuses on a single obsession: timing precision audio. Where many components chase higher bit depths or sample rates, Quartet concentrates on reconstructing the micro‑timing of musical transients that define space, texture, and pitch. It is built to work in tandem with Chord’s high-end DAC lineup and is expressly voiced to push the flagship DAVE DAC to its full 768 kHz capability. The result is a component aimed squarely at serious digital audio collectors who already operate in the high-end DAC tier and want their playback chain to act less like a data pipeline and more like a time‑aligned reconstruction system. Quartet is intended not as a marginal tweak, but as a foundational upgrade in reference audio precision.
Four Million Filter Taps and Five FPGAs: Inside Blackbird WTA
At the heart of Quartet is the new Blackbird WTA filter, a dramatic escalation of Chord’s filter tap technology. The previous M Scaler deployed around one million taps; Quartet multiplies that to four million taps distributed across five Xilinx FPGAs, delivering roughly five times the processing power of the DAVE DAC itself. In practice, taps represent the complexity of an interpolation filter—the more taps, the more finely the system can infer what should exist between discrete digital samples. Chord claims Blackbird WTA delivers a tenfold improvement over its previous WTA generation, with most coefficients approaching the theoretical sinc function ideal for reconstruction. Unlike FFT convolution approaches that operate in the frequency domain, Quartet’s filtering is executed directly in hardware, explicitly to avoid additional timing errors. For high-end DAC owners, this architecture promises higher timing precision audio, sharper transient focus, and a more stable, three‑dimensional soundstage.
Why Timing Precision Matters More Than Ever for Digital Collectors
Rob Watts likens conventional digital audio to putting a steak through a mincer and then trying to rebuild the original cut from the mince. The missing element, in his view, is precise transient timing—the leading edges of notes that cue the brain about instrument identity, spatial location, and the boundaries of a recorded acoustic. When those edges are smeared or shifted, depth collapses and complex mixes flatten, even if bit‑perfect data appears intact. Quartet’s four‑million‑tap engine is designed to interpolate the “missing” information with minimal timing error, effectively trying to reassemble the steak rather than merely seasoning the mince. For collectors with extensive digital libraries, this emphasis on timing rather than simple resolution numbers is crucial: it directly targets the sense of realism that makes familiar recordings feel newly alive, particularly through revealing speakers and high-end DACs that can expose these micro‑temporal corrections.
Built-In ADC: Extending Reference-Grade Processing to Analog Sources
A major first for Chord’s digital audio upscaler line is Quartet’s integrated analog‑to‑digital converter. This custom Pulse Array ADC allows analog sources—turntables, tape machines, or any line‑level component—to be digitised and then passed through Blackbird WTA. Traditionally, ADCs risk aliasing, where ultrasonic noise folds back into the audible band, compromising clarity and timing. Standard half‑band filters can control this but often at the expense of temporal accuracy. Quartet counters with proprietary decimation filters that clean up its 104 MHz noise‑shaper output while aiming to avoid added noise floor modulation. For vinyl enthusiasts and tape aficionados, that means their most cherished analog front ends can now feed into the same timing‑focused DSP chain as their digital libraries. In a single chassis, Quartet becomes a hub capable of imposing reference audio precision across both digital and converted‑analog sources, unifying the entire playback ecosystem.
System Synergy and the Future of High-End Digital Playback
Quartet is not intended as a standalone trophy but as the digital engine at the core of a reference playback chain. Its native synergy with Chord’s DAVE and other high-end DAC models lets it handle the heavy lifting of interpolation while the downstream DAC focuses on conversion linearity and analogue output quality. For system builders, the modularity matters: existing premium DACs can be elevated without replacement, and analog sources no longer sit outside the digital timing regime. In aggregate, the four‑million‑tap filter, five‑FPGA architecture, and integrated ADC represent a notable engineering leap in digital-to-analog conversion strategy. Instead of treating resolution, jitter, and noise as isolated specs, Quartet reframes high‑end digital as a timing problem to be solved holistically. For committed audiophiles, it signals a future where reference‑grade sound quality hinges less on sheer format numbers and more on how convincingly time itself is reconstructed.