AudioQuest DragonFly Cobalt USB DAC/Headphone Amp

AudioQuest DragonFly Cobalt — USB DAC / Preamp / Headphone Amplifier

The DragonFly Cobalt is the flagship of AudioQuest's DragonFly family — the most refined expression of a product category that AudioQuest essentially created in 2012. It sits above the DragonFly Black and DragonFly Red, sharing the same thumb-drive form factor and plug-and-play simplicity but upgrading every critical element of the design: a more advanced DAC chip with a different reconstruction filter, a faster microcontroller with lower current draw, dedicated power-supply noise filtering, the same ESS headphone amplifier and 2.1V output as the Red, and a 10% smaller case. Where the DragonFly Black delivers a transformative improvement over built-in audio and the Red adds headphone-driving authority, the Cobalt goes further by stripping away layers of background noise and digital artefact that are not even apparent until they are removed.

ESS ES9038Q2M: Slow Roll-Off and Why It Matters

The DragonFly Black uses the ESS 9010, the Red uses the ESS 9016, and the Cobalt steps up to the ESS ES9038Q2M — ESS's flagship mobile DAC chip at the time of its introduction. All three are 32-bit Sabre converters, and all three use minimum-phase digital reconstruction filters (which concentrate time-domain ringing after the impulse rather than splitting it before and after, avoiding the perceptually unnatural pre-echo of linear-phase designs). The key difference is that the 9038Q2M in the Cobalt uses a minimum-phase slow roll-off filter, while the chips in the Black and Red use standard minimum-phase filters.

The distinction lies in the trade-off between frequency-domain precision and time-domain behaviour. A standard (or "fast") roll-off filter achieves very steep attenuation above the Nyquist frequency, suppressing ultrasonic aliasing images by 100dB or more — but the steepness of the filter produces extended time-domain ringing that can smear transient detail. A slow roll-off filter relaxes the cutoff slope, which means some ultrasonic content rolls off more gradually and aliasing suppression is reduced (Stereophile's measurements show ~34dB suppression in the Cobalt versus >110dB in the Red). In return, the time-domain ringing is dramatically shorter — almost impulse-like — resulting in a more natural transient response. The ultrasonic aliasing products that are less attenuated are well above the audible frequency range; the improvement in transient clarity is within it. AudioQuest describes the sonic result as a combination of warmth and detail that is emotionally engaging without becoming fatiguing — an important quality for a device likely to be used with headphones for extended listening sessions.

Like the Black and Red, the Cobalt's analogue circuits are direct-coupled from the ESS DAC chip's output, with no coupling capacitors or extraneous components in the signal path.

Power-Supply Noise Filtering: What AudioQuest Learned from Cables

The Cobalt's most significant engineering advancement over the Red is its dedicated power-supply filtering — a technology informed by AudioQuest's research into noise-dissipation for their cable products, now applied to the unique electrical environment of a portable DAC. The problem it addresses is specific and increasingly severe: every device the DragonFly plugs into is a source of high-frequency electrical noise. WiFi radios, Bluetooth transmitters, cellular modems, and the switching power supplies that feed them all generate interference that travels along the USB power line into the DAC, contaminating the analogue audio signal at the point of conversion.

The DragonFly Black and Red have no dedicated filtering for this noise — they rely on the inherent power-supply rejection of their DAC chips and the low-noise characteristics of the Microchip microcontroller. The Cobalt adds purpose-built filtering circuitry between the USB power input and the audio circuitry, designed specifically to attenuate the frequencies at which WiFi (2.4GHz and 5GHz), Bluetooth (2.4GHz), and cellular signals (700MHz–2.6GHz) operate. The result is a lower noise floor, which means the very quietest musical details — the decay of a note, the breath of a singer, the ambient space of a recording — are preserved rather than masked by the electrical noise of the host device. This matters most with high-resolution audio, where the additional information captured at higher bit depths and sample rates is precisely the low-level detail that noise would otherwise obscure.

Upgraded Microcontroller

The Cobalt uses Microchip's PIC32MX274, replacing the PIC32MX found in the Black and Red. The 274 increases processing speed by 33% while drawing less current — an improvement that benefits both audio performance (faster processing reduces the microcontroller's contribution to timing uncertainty) and battery life on mobile devices. As with the Black and Red, the microcontroller runs Gordon Rankin's Streamlength asynchronous USB code, which commands the timing of data transfer from the host device rather than accepting whatever the computer or phone sends. Asynchronous mode ensures that the DAC's own high-precision clock governs the conversion timing, not the host device's USB bus clock, which is optimised for data throughput rather than audio fidelity.

The Cobalt retains the monoClock architecture shared across the DragonFly range — a single ultra-low-jitter clock generated from the ESS DAC chip runs all functions: the DAC conversion, the headphone amplifier, and the microcontroller. Where many portable DACs use separate clocks for different subsystems (introducing inter-clock interference and timing uncertainty), the single-clock approach eliminates this noise source entirely.

ESS Headphone Amplifier and Bit-Perfect Volume Control

The Cobalt shares its headphone amplifier with the DragonFly Red: the ESS Sabre 9601, which includes a bit-perfect digital volume control integrated into the DAC chip itself. This is a fundamentally different approach from the DragonFly Black's analogue volume control. In the Black, the host device sends a command that adjusts a 64-step analogue attenuator — effective, but the signal passes through the attenuator circuit regardless. In the Cobalt (and Red), volume adjustment happens in the digital domain at 64-bit precision before conversion, meaning the full dynamic range and signal-to-noise ratio of the DAC are preserved at every volume setting. The practical difference is most apparent at lower listening levels, where the bit-perfect approach maintains detail and dynamic contrast that an analogue attenuator would compress.

The maximum output is 2.1V RMS — a significant step up from the Black's 1.2V and identical to the Red's. This higher output voltage means the Cobalt can drive a much wider range of headphones, including power-hungry, low-efficiency over-ear models that the Black would struggle to control at dynamic peaks. Where the Black is best suited to headphones above ~95dB/mW sensitivity, the Cobalt and Red comfortably handle headphones down to 16 ohms impedance and beyond, with the authority and grip needed to maintain transient speed and bass control into demanding loads.

Output Modes and System Integration

Like all DragonFly models, the Cobalt operates in two modes. Connected directly to headphones or powered speakers, it functions in variable-output mode with the host device's volume slider controlling the listening level via the internal bit-perfect volume control. Connected to a preamplifier, integrated amplifier, or AV receiver input via a 3.5mm-to-RCA cable (such as AudioQuest's own Evergreen or Golden Gate 3.5mm-to-RCA variants), you set the host volume to maximum for a fixed 2.1V line-level output — comfortably driving any domestic line-level input — and control volume from the amplifier. In this second configuration, the Cobalt serves as a high-quality external DAC that happens to cost a fraction of a traditional separates-format converter, with the noise-dissipation filtering providing a genuinely useful advantage over the Black and Red when connected to a laptop or phone running multiple wireless radios.

MQA Rendering

The Cobalt is an MQA Renderer, completing the final unfolding stage of MQA decoding when a Core signal is provided by a compatible application such as Tidal, Audirvana, or Roon. The LED glows purple during MQA playback. As with the Black and Red, MQA rendering is built into the firmware and costs nothing additional.

Compatibility and LED Indicator

The DragonFly Cobalt is compatible with macOS (10.6.8 and later), Windows (7 and later), and Linux computers, as well as iOS devices (using Apple's Lightning-to-USB 3 Camera Adapter, or a USB-C adapter for newer devices) and Android devices running Lollipop 5.0 or later. No drivers are required on any platform. The Cobalt includes a form-fitting DragonTail USB-A to USB-C adapter (built to AudioQuest's Carbon-level USB cable specification), accommodating the growing number of laptops, tablets, and phones that have moved to USB-C.

The Cobalt uses a different LED colour scheme from the Black and Red to indicate sample rate: red for standby, green for 44.1kHz, blue for 48kHz, yellow for 88.2kHz, and light blue for 96kHz. Purple indicates MQA rendering, as with all DragonFly models. Files above 96kHz will play — the host device's software downsamples them before sending to the DragonFly.

Build and Design

The Cobalt is housed in an aluminium case with a metallic cobalt-blue finish — visually distinctive from the matte-black of the Black and the matte-red of the Red. At 57.5mm × 18.6mm × 11.9mm, it is approximately 10% smaller than the Black and Red (which measure 62mm × 19mm × 12mm), making it the most pocket-friendly DragonFly to date. The USB Type-A connector is gold-plated, and the included DragonTail USB-C adapter means the Cobalt is ready for use with USB-C devices straight out of the box. A leatherette travel pouch is included for protection.

The DragonFly Family: Choosing Your Level

All three DragonFly models share the same Streamlength asynchronous USB platform, the same monoClock single-clock architecture, the same direct-coupled analogue output topology, and the same MQA rendering capability. The DragonFly Black is the entry point — the ESS 9010 with analogue volume control and 1.2V output, ideal for efficient headphones and external amplifiers. The DragonFly Red steps up with the ESS 9016, the ESS 9601 headphone amplifier with bit-perfect digital volume control, and 2.1V output — the choice when headphone-driving authority and dynamic range at low volumes are priorities. The Cobalt adds the ESS 9038Q2M with its slow roll-off filter for superior transient naturalness, the PIC32MX274 for faster processing and lower power draw, and the dedicated noise-dissipation filtering that sets it apart from every other DragonFly — it is the model for listeners who want the lowest possible noise floor and the most refined, fatigue-free presentation that this form factor can deliver.