The Tight and Tasty Questyle Q192 DAC/Headphone Amp
Questyle Q129 DAC/Headphone Amp ($649)
Questyle Audio Engineering is on the rise. With reviews completed or in progress from a number of audio review sites, the company's visibility is growing rapidly. Everyone I've talked to, from end-users to journalists, seems very impressed thus far. Most of the focus centers around the decidedly high-end CMA800R current-mode amplifier, which at $1,500 is not all that accessible to most people. Questyle isn't limited to amps: their CAS192 balanced DAC is a top performer as well. But again, at $2k, it's not really a mass market device.
Questyle wanted to show the community that they can do affordable gear without sacrificing quality. To that end, they submitted their Q192 for review. I've spent some time with it in several different systems and have come to really enjoy what it has to offer. At $649 it isn't what I'd call "cheap" but is more approachable for most users compared to their flagship gear.
So what exactly is the Q192? Questyle basically takes trickle-down tech from their higher models and distills it into a relatively compact, all-in-one unit. The result is a USB DAC with integrated headphone amp, preamp functionality, and USB to SPDIF conversion. The aim is not just to produce a versatile device, but a truly excellent performer in each category. Easier said than done.
The Q192 is what I'd call a "smallish" device, which means it barely fits in the small category as I define it. The all-aluminum enclosure is roughly 10 inches deep, 5 inches wide, and a bit over 2 inches tall. That makes it small enough for most situations, thought I did find the depth a bit much at times when using it for a desktop system. In comparison to something like the AMI DDH-1, those extra inches of depth can make a big difference.
Build quality seems on par with Questyle's higher-end CMA800R and CAS192which is to say "very nice indeed". I have absolutely no complaints here. If we look at something like the Parasound Zdac or the previously mentioned AMI DDH-1, the Q192 falls perfectly in line. I actually think it may be nicer than either when it comes to the texture and finish of the enclosure... not the type of thing that can be easily captured in photos, but it's something I notice in person.
Simplicity is a strength here. Compared to the DDH-1, the Q192 has a lot less going on. That's bad if you want sample rate indicators and separate jacks for 1/4" and 1/8" plugs, but good if you value aesthetics and ease of use. You decide which style fits you best.
It really doesn't get much more simple than this: front panel has a big volume knob, an input selector, and one more switch to toggle between fixed and variable output. The small LED power indicator and a single 1/4" jack round out the entire front panel. That's it. Nice and easy.
Around back, things are a bit more complex, but not by much. We get inputs in both USB and coaxial, a coaxial output (for DDC functionality), and a pair of analog outputs which can be used to feed an external amp or active speakers. Add in the IEC cable connection with a hard on/off switch, and we're done with the rear panel.
Popping the cover shows some thoughtfulness in both layout and component selection. There's a custom shielded toroidal transformer with separate windings for digital and analog. A dozen Shottky rectifiers, Nichicon FineGold stiffening capacitors, and 15 independent power regulators combine to provide robust, clean power to the device.
For inputs, the Q192 shares traits with its more expensive CAS192 sibling. The USB chipset is custom branded by Questyle, but judging by the driver package it's actually the C-Media CM6631A asynchronous solutionas also seen in the Schiit Gungnir and Asus Xonar STU among others. Questyle employs their "3X Clock Structure" system which means 3 independent, custom made, ultra-low phase noise clocks: one each for data transmission, 44.1kHz, and 48kHz signals (and their direct multiples). There's also a mystery chip (complete with Questyle branding) near the USB receiver, that I suspect to be a Field Programmable Gate Array (FPGA for short). Questyle says they prefer to keep it a secret, so I didn't press the issue. SPDIF receiver is the excellent Wolfson WM8805 which features an "elastic buffer" to absorb timing errors without modifying the original samples in any way. Jitter is scrubbed to a low 50ps RMS. Both inputs support PCM signals up to 24-bit/192kHz.
The DAC chip used here is the affable Wolfson WM8470. I've seen this chip used in everything from quality budget stuff like the NAD C545BEE, to rather upscale gear - Lyngdorf CD-2, YBA Heritage CD100, and Linn Majik. It's not a cutting edge Sabre chip and it's no longer even the top model from Wolfson (that would be the newer WM8741 as used in Questyle's CAS192 and PS Audio's PerfectWave to name just a few) but it can still sound quite good when properly done. And I'd say that is indeed the case here.
While we place a lot of emphasis on the choice of DAC chip, the analog output stage is arguably more important in determining the final sound quality. Key components here include WIMA FKP2 capacitors and ADI OP275 opamps used for buffering. The headphone stage uses a pair of OPA627 opamps feeding discrete transistors in a unique topologythat would be Questyle's current-mode amplification technology derived from the flagship CMA800 series. You can read my review of that device for more detail but essentially it involves converting the voltage input to the current domain for amplification, then back to voltage prior to output. The low impedance, ultra-high speed feedback loop is key to achieving exceptional measured performance (very low THD, great SNR, 500kHz bandwidth, and practically no TIMD). Questyle's particular implementation is unique and while you can find vaguely similar technology in gear from Krell or Bakoon, none of their stuff comes in at anything near affordable pricing. The one potential weakness I see in the specs: Q192 is not a powerhouse in terms of output. It is rated at 100mW RMS into a 32 ohm load, and 60mW RMS into 300 ohms. Not the highest I've ever seen, though voltage swing is decent at 4V RMS. On the plus side, output impedance is so low as to not matter (under 1 ohm)another Questyle trend that I'd like to see others follow.
Alrighty, flip the page and we'll turn this thing on.