Quartet: A Reference Digital Audio Upscaler Built Around Timing Precision
Chord Electronics’ new Quartet digital audio upscaler is being positioned as one of the most important components in the company’s history, and its mission is clear: fix timing errors in digital playback rather than simply boosting resolution figures. Designed to partner with Chord DACs and fully exploit the flagship DAVE’s 768 kHz capability, Quartet focuses on how accurately it can reconstruct the precise arrival of musical transients. These micro-events—tiny leading edges of notes—carry critical information about pitch, timbre, and spatial cues. When their timing is even slightly off, the result can be flattened dynamics, blurred imaging, and a less convincing sense of musicians in real space. Quartet’s design prioritises timing precision DAC performance over headline sample rates, aiming to recover low-level detail and ambience that often remain hidden in digital music files, even in high-end audio reconstruction chains.
Four Million Filter Taps and Five FPGAs: Blackbird WTA Takes Flight
At the heart of Quartet is Chord’s new Blackbird WTA filter, a radical evolution of the company’s proprietary interpolation technology. Where the earlier M Scaler deployed one million filter taps audio enthusiasts already considered extreme, Quartet pushes to four million taps distributed across five Xilinx FPGAs. In simple terms, taps describe how complex and finely grained the reconstruction filter is; more taps allow the filter to infer with greater accuracy what should exist between the original digital samples. Chord claims this Blackbird implementation delivers a tenfold improvement in transient timing accuracy over its previous WTA filter and five times the FPGA processing power of the DAVE DAC. Crucially, Quartet executes its filtering directly in hardware rather than relying on FFT convolution, which Chord argues can reintroduce timing errors. The target is a reconstruction filter whose coefficients approach the theoretical ideal sinc function, maximising timing precision for demanding listeners.
Why Timing Precision Matters in Digital Audio Reconstruction
Quartet is explicitly designed to tackle what Chord’s digital designer Rob Watts describes as the core weakness of conventional digital audio: timing. Converting analogue sound into digital, then back again, can disrupt the exact arrival time of transients, the sharp leading edges that define the character of instruments and the boundaries of recorded space. When these are smeared or misaligned, the brain has to work harder to parse pitch, locate performers, and perceive depth. The result can be a flatter, less engaging sound, even from the best digital audio upscaler or DAC. By using an ultra-long filter with four million taps, Blackbird WTA aims to reconstruct missing information between samples with far greater temporal accuracy. Chord argues this yields cleaner bass pitch definition, more realistic timbre, and a more stable, three-dimensional soundstage, revealing low-level details and reverberation that standard reconstruction filters can leave buried.
Built-In Pulse Array ADC: Bringing Analogue Sources Into the Digital Timing Chain
In a first for a Chord upscaler, Quartet integrates a custom Pulse Array analogue-to-digital converter so that analogue sources can traverse the same timing-focused digital pipeline as files and streams. This ADC is designed to address aliasing—ultrasonic noise folding back into the audible band—which Chord says can corrupt timing information. Instead of relying on conventional half-band filters, Quartet uses proprietary decimation filters to clean up its 104 MHz noise-shaper output while avoiding additional timing compromises. For audiophiles, this means turntables, tape decks, and other line-level sources can be digitised with minimal timing distortion before being upscaled. The Quartet then applies its four-million-tap Blackbird WTA filter to these newly digitised signals, offering high-end audio reconstruction benefits previously reserved for purely digital sources. In effect, the entire system becomes a timing precision DAC front-end for both analogue and digital music libraries.
Positioning Quartet in the High-End Digital Playback Ecosystem
Quartet’s engineering ambition clearly targets system builders chasing reference-grade digital audio chains. Its role is to sit between a source and a DAC, providing ultra-precise upscaling and timing correction before conversion back to analogue. With four million taps and hardware-based filtering, it extends the concept introduced by the M Scaler rather than replacing it with a simple spec bump. The inclusion of an ADC broadens its appeal, allowing owners of serious vinyl and tape rigs to integrate those sources into a single digital timing architecture. For listeners already invested in Chord’s DAVE or other Pulse Array DACs, Quartet functions as a dedicated timing engine designed to unlock more information from existing libraries. While its complexity will appeal most to experienced enthusiasts, the underlying promise is straightforward: reduce timing error to recover hidden detail, making familiar recordings sound more lifelike, coherent, and spatially convincing.