Although Questyle may be a new name to some audiophiles, the company has been in existence for several years. It combines two complementary operations: Questyle Audio Technology Co. Ltd, China, and Questyle North America Inc., USA. All Questyle products are manufactured by its “strategy partner manufacturing center,” Foxconn, which also makes many Apple products.
The component under review, the Questyle QP1R portable music player, was in development for over three years. Questyle’s goal was “to make it possible for true music lovers and professional audiophiles to enjoy the same hi-fi listening experience achieved in state-of-the-art home-based systems in a portable body.”
Questyle has two versions of its portable player. The standard QP1 lists for $599, while the QP1R lists for $899. According to Questyle, the QP1R uses higher-quality components as well as a more critical approach to the audio circuit. The QP1R also produces lower distortion; the QP1R’s THD+N is 0.0006%, while the QP1 THD+N is 0.0015%. The QP1R also employs a different PCBA, a larger internal storage chip (32GB), and a different version of its operating software.
The unique technological feature of Questyle digital products is their patented “current mode amplification” Class A output circuitry. This circuit originally appeared in Questyle’s flagship headphone amplifier, the CMA800. Jason Wang, the CEO and chief designer for Questyle, developed the first current-mode circuit in 2004, while he was working on a communications circuit project in school. The first prototype had a bandwidth of 1MHz!
After graduation Wang went to work for an IC design firm where he continued to refine his current-mode amplification design with the help of several mentors, including Dr. Charles from the University of California, Los Angeles. The CMA800, the world’s first current-mode headphone amplifier, was introduced in 2007. With the CMA800, Wang solved the technology issue of how to mass-produce the current-mode circuit using discrete components, and the Questyle brand was born.
In the current-mode amplifier, transistors amplify the signal’s current via a circuit operating in a pure Class A. The output stage can be either a Class A or AB voltage amplifier. The CMA design reduces capacitance between the transistors so the circuit operates at a very low impedance, which improves the speed and full-power capabilities of the entire amplifier. The current-mode amp also employs a negative feedback loop that is hundreds of times faster than that of conventional voltage amplifiers. This CMA circuitry not only vastly reduces transient intermodulation distortion; it also contributes to wider overall bandwidth.
On the digital side, the QP1R uses a three-clock integrated circuit with FIFO asynchronous structure and three voltage-stabilized power stages. The QP1R employs Cirrus Logic’s flagship DAC chips (CS4398), along with a customized clock from NDK with phase noise lower than -150dB. Other premium parts in the QP1R include power inductors from Wurth, an ALPS encoder, and Nichicon F95 tantalum capacitors.
The QP1R chassis is milled out of a solid piece of aluminum and merged with a Gorilla Glass front and back, which not only reduces the QP1R’s overall weight but also provides a better environment for EMI sensitive circuits.