Questyle CMA Fifteen

Questyle CMA Fifteen: a benchmark headphone amp and DAC

Fifteen years of technological evolution concentrated in a compact chassis: the CMA Fifteen marks an important milestone for Questyle. This headphone DAC-amp builds on the fundamentals of the CMA Twelve while introducing a new architecture that, for the first time, combines a current-output DAC chip with amplification stages operating on the same principle. The result is an audio chain in which the signal travels end-to-end without any intermediate conversion between current and voltage.

An architecture that eliminates unnecessary conversions

Most high-end DACs deliver their signal in the form of current. Conventional amplifiers, however, require a voltage input, which entails an intermediate conversion stage – an additional link in the signal path. The CMA Fifteen bypasses this step by directly coupling the ESS ES9038PRO chip to four current-mode amplifiers, a fully symmetrical topology that Questyle has patented (US 9614483 B2). This approach, called Current Mode², preserves signal integrity from digital-to-analog conversion all the way to the headphone transducers.

The conversion stage supports PCM formats up to 768 kHz in 32-bit and native DSD512. Full MQA decoding is also integrated, indicated by dedicated LEDs on the front panel: green for standard MQA content, blue for MQA Studio files.

Power and settings suited to all headphones

Three headphone outputs share the front panel: unbalanced 6.35 mm jack, balanced 4.4 mm jack, and 4-pin XLR. In balanced mode, the amplifier delivers 765 mW into 300 ohms and 2 W into 32 ohms, figures that allow it to drive both power-hungry planar headphones and high-impedance models. The unbalanced output delivers 1.5 W into 32 ohms, almost double that of the CMA Twelve.

The adjustment options make it possible to tailor the unit’s behavior to the headphones in use. A bias selector on the front switches between two modes: High extends operation in Class A, while Standard saves energy by moving earlier into Class A/B. Four micro-switches located under the chassis one for each of the four amplifiers set the gain to either Standard or Low. This layout may seem inconvenient for frequent changes, but it guarantees perfect channel balance, since all four stages must be adjusted simultaneously.

Comprehensive connectivity and analog input

The rear panel concentrates a variety of inputs that cover most setups. Two USB ports are provided: Type-C (priority if both are connected) and Type-B, both supporting high-resolution formats up to DSD512. The optical and coaxial inputs accept PCM streams up to 192 kHz/24-bit. Bluetooth 5.0 supports SBC, AAC, and LDAC codecs – the latter allowing transmission up to 96 kHz/24-bit. The aptX codec, however, is not offered.

The addition of an RCA analog input is one of the notable changes compared to the previous model. It allows you to integrate a turntable (via an external phono preamp) or any other analog source into the system, turning the CMA Fifteen into a truly versatile audio hub.

Preamplifier function for active speakers

Beyond headphone listening, the CMA Fifteen can serve as a preamplifier to feed active speakers or a power amplifier. The RCA and balanced XLR outputs offer two voltage levels: Standard mode (2 V on RCA, 4 V on XLR) is suitable for consumer equipment, while Studio mode (14 dBu on RCA, 20 dBu on XLR) targets professional setups. A second switch lets you choose between variable volume (ADJ) and fixed level (FIX), the latter disabling the potentiometer for unity gain.

Measurements for the preamp section show a signal-to-noise ratio above 119 dB on XLR and harmonic distortion of 0.0003%, figures that place this section on par with dedicated preamplifiers.

Construction designed for acoustic neutrality

The 6063 aircraft-grade aluminum chassis, 10 mm thick, is not just about looks. This thickness and the machining precision (±0.02 mm) are intended to minimize mechanical resonances that could affect sensitive circuits. Questyle has also studied front-to-back mass balance once cables are connected, in order to reduce parasitic vibrations.

Inside, the PCB reveals a carefully organized layout that clearly separates the DAC, amplification, and power supply sections. Components come from renowned manufacturers: Nichicon FW and WIMA capacitors, military-grade DALE resistors. The integrated linear power supply avoids the need for an external brick, while an XMOS controller handles USB inputs on a dedicated daughterboard. An automatic protection system cuts the outputs in the event of a detected fault.

The included remote control allows you to adjust volume, select sources, and mute the sound without leaving your seat.

Technical specifications

DAC section

• DAC chip: ESS ES9038Pro (high-end, current-output mode)
• Architecture: Current Mode² (DAC and amplifiers in current mode)
• Maximum PCM decoding: 768 kHz / 32-bit
• Native DSD decoding: DSD512
• DSD DoP: DSD256
• MQA: full decoder (Full / Core decoder)

Amplification section

• Amplifier type: 4 groups of current-mode amplifiers (patented technology)
• Architecture: fully discrete, topological, symmetrical
• Patent: US 9614483 B2 (global PCT)
• Total harmonic distortion + noise (THD+N):
  • Less than 0.0003% at 300 Ω
  • Less than 0.001% at 32 Ω
• Frequency response: DC – 22 kHz (± 0.2 dB) at 48 kHz / 24-bit
• Components:
  • Nichicon FW capacitors
  • WIMA capacitors
  • DALE military-grade resistors

Headphone outputs

• Available connectors:
  • 6.35 mm unbalanced jack
  • 4-pin balanced XLR
  • 4.4 mm balanced jack
• Output power:
  • 6.35 mm unbalanced jack: 188 mW at 300 Ω, 1.5 W at 32 Ω
  • 4.4 mm balanced jack: 765 mW at 300 Ω, 2 W at 32 Ω
  • 4-pin balanced XLR: 765 mW at 300 Ω, 2 W at 32 Ω
• Signal-to-noise ratio (SNR):
  • 6.35 mm unbalanced jack: greater than 117 dB
  • 4.4 mm balanced jack: greater than 120 dB
  • 4-pin balanced XLR: greater than 120 dB

Digital inputs

• USB Type-C (priority): PCM 44.1 – 768 kHz / 32-bit, native DSD512, DoP DSD256, MQA
• USB Type-B: PCM 44.1 – 768 kHz / 32-bit, native DSD512, DoP DSD256, MQA
• Optical (OPT): PCM 44.1 – 192 kHz / 24-bit
• Coaxial (S/PDIF): PCM 44.1 – 192 kHz / 24-bit
• Bluetooth:
  • Supported codecs: SBC, AAC, LDAC
  • Maximum LDAC quality: 96 kHz / 24-bit, 990 kbps
  • Certification: Sony LDAC partner

Analog connections

• Analog input:
  • RCA: 2 Vrms
• Preamplifier outputs:
  • RCA: 2 V (Standard mode), up to 14 dBu (Studio mode)
  • XLR: 4 V (Standard mode), up to 20 dBu (Studio mode)
• Preamplifier specifications:
  • THD+N: 0.0004% (RCA), 0.0003% (XLR)
  • SNR: greater than 116 dB (RCA), greater than 119 dB (XLR)
  • Frequency response: DC – 22 kHz (± 0.2 dB)

Settings and adjustments

• Bias: High / Standard (front panel selector)
• Gain: Standard / Low (4 switches under the unit)
• Preamplifier output level: Standard / Studio (rear panel selector)
• Preamplifier volume: ADJ (variable) / FIX (fixed) (rear panel selector)

System compatibility

• Windows XP / Vista / 7 / 8: Questyle ASIO driver required
• Windows 10 and later: driverless (DoP DSD256), with driver (native DSD512)
• macOS: natively compatible
• Linux: compatible
• Smartphones: audio OTG compatible
• Apple Music Lossless: supported

Build and design

• Chassis: aerospace-grade 6063 aluminum, 10 mm thick
• Machining precision: ± 0.02 mm
• Anti-resonance design: front / rear balanced
• Markings: laser engraving
• Finish: classic Questyle black
• Operating temperature: less than or equal to 45 °C
• Indicators: amber LED, green LED (MQA), blue LED (MQA Studio)

Additional functions

• Preamplifier function: can be used with a turntable or active speakers
• Output protection: automatic cutoff in case of anomaly
• USB priority: Type-C takes priority if both USB ports are connected
• MQA indicator: green LED (MQA), blue LED (MQA Studio)

Certifications and technologies

• Current Mode Amplification (Questyle patented technology)
• ESS SABRE Pro / SABRE HiFi
• MQA (full decoding)
• Sony LDAC (certified partner)