Special thanks to Questyle’s Leo Jiang and Nancy Du for making this review possible, and for their much-appreciated continued support.
If you’ve been an active audiophile or hi-fi enthusiast over the past decade or so, the name Questyle should be very familiar to you. The Shenzhen-based company, founded in 2012, is one of the most progressive makers of desktop and portable audio playback systems in the world, ably supported by Foxconn, the world’s foremost electronics manufacturer.
One of Questyle’s numerous claims to fame is its patented current mode amplification technology, invented (and later patented) by the company’s founder Jason Wang back in 2006. I’ll discuss this technology in more detail later in this review, but suffice it to say it’s no coincidence that the company’s flagship desktop devices are all prefixed with ‘CMA’.
Which brings us to the star of this particular review: the new CMA18 Portable. Historically, Questyle has made DAC/amp devices in three formats – dongle (portable), DAP (portable), and desktop. While both the dongle and desktop lines have been fairly active recently (with the M15 and CMA18 Master devices respectively), the company’s most recent DAP, QP-M, was released back in 2019.
The new CMA18 Portable doesn’t quite fit into either the dongle or desktop categories, although the fact that Questyle lists it under desktop devices should be an indication of its performance tier. As such, even though CMA18 Portable is very much a portable device – as its fairly diminutive and battery power-only design would suggest – it’s also significantly more powerful and versatile than any of Questyle’s dongles and DAPs, with performance figures that wouldn’t look out of place in a full-size desktop device.
Portability and power
When we think of truly portable DAC/amps, one of the first compromises we expect them to make is power output. The more power an amplifier generates, the more heat it produces, the less efficient it becomes, and the more battery it consumes. This is generally true for all types of amplification, but it’s also where current mode amplifiers offer a distinct advantage over more traditional amplification designs.
Without getting bogged down in the science, the elevator pitch for Questyle’s patented SiP (single-ended input, push-pull output) current mode amplification technology is that all amplification is done in the current, rather than voltage, domain. Think of it as controlling the flow of water through a pipe, with the precise control of the flow having knock-on benefits for speed and efficiency.
In theory, this means the technology helps to greatly reduce distortion in the amplified signal, and also mitigates many timing-related issues common to typical voltage mode amplifiers. Current mode amplifiers have better transient response than voltage amps, allowing them to respond more quickly to changes in the input signal and therefore reduce signal artefacts like pre- and post-ringing. They also reduce phase distortion, which results in more accurate sound reproduction.
Most importantly, though, current mode amplifiers are far more power efficient, making them better-suited for driving low-impedance loads, such as IEMs and headphones, and contributes to better sound quality in portable audio devices.
CMA18 Portable is fitted with four sets of current mode low-power PCT SiP units, capable of delivering a sustained power output of 1,000mW (1 watt) at 32 ohms and instantaneous output current up to 2 amps. While these numbers might look comparable to those from some of today’s high-powered DAPs and portable amps, the efficiency of Questyle’s current mode technology means the numbers quoted are conservative relative to real world performance, while traditional amps often fall well short of their quoted specs in practice.
Of course, these numbers and theoretical musings are all good and well; as you’ll soon see, actual performance is what really matters.
Packaging and accessories
When I first unpacked the CMA18 Portable, I was admittedly underwhelmed. Thankfully, it turns out the plain white cover is just that; underneath is a precision-cut clamshell box that opens up to reveal one of the more premium unboxing experiences I’ve had to date.
The first thing you’ll see is the transparent glass panel that – and take my word for it – looks even better in person than these photos. Set inside a foam insert on the right-hand side of the box, Questyle cleverly used the space around the frame to label the various features and functions, giving you a virtual product tour before you even get started.
On the opposite side of the clamshell is another foam panel with inserts for the various cables and connectors. You get a long USB-C to C charging cable, and two shorter USB-C to C (OTG) and USB-C to Lightning cables for connecting to portable devices (CMA18 Portable is MFi-certified for iPhone and iPad).
You also get a USB-C to A adapter for connecting to a PC or Mac, and an optical/Toslink to 3.5mm adapter for connecting your desktop DAC, TV or any other optical-out device to the optical input.
All the cables are finished in an attractive material sheathing that feels very premium to the touch. My only complaint is the number of cables included; it would have been useful to get at least one analogue-to-analogue cable, single-ended or balanced, and maybe also one of Questyle’s 3.5mm-to-RCA cables for connecting an external amp or speakers. For the price I would have also liked to see a case and screen protectors included in the box.
But these are small nitpicks; everything you need to get started is provided, and all of the extra accessories are available to purchase elsewhere.
As mentioned, I was also sent the custom leather case, which fits like a glove, has a window for the gain and hold switches, and embossed markers for each of the buttons, making it easy to operate the device when cased. Unlike many cases cut too loosely, this one fits tight, and it takes some effort to remove once inserted (that’s a good thing, by the way). The leather also seems to be of very high quality, with a grippy texture that makes it much easier to handle.
Continue to design and specs…
