Questyle M12 USB DAC/Headphone Amplifier: Review

Dongle DACs have become a hot commodity in the personal audio category and it was only a matter of time before the more established brands in the DAP and desktop headphone amplifier segments introduced their own products to compete with THX, AudioQuest, Helm Audio, and Clarus. Questyle operates a very high-end factory in Shenzen and they’ve been a major player in the Head-Fi world since 2012. The $139 Questyle M12 USB DAC/Headphone Amplifier is not just any Dongle DAC.

Questyle has been making DAPs since 2015 after releasing a series of desktop current mode amplifiers starting in 2012. With changing times come changes in product lines.

The Chinese manufacturer does not cut corners with any of its products and the prices reflect that; the build quality of the existing Questyle products is exceptionally high and there is no shortage of accolades from both the press and customer base.

If you’re considering products from Topping, you probably need to consider Questyle as well as both companies pack an enormous amount of leading edge technology into all of their products. The Questyle M12 is an interesting option in the category that is affordably priced.

The M12 would classify as a mid-sized Dongle DAC (51mm L x 16.5mm W x 8.1mm D) that is around the size of a package of gum. Questyle has offered a gold finish on a number of its products but the M12 is only available in Black or Silver.

If you are familiar with Dongle DACs like the EarMen Sparrow, HiBy FC3, or HiliDAC Audirect Beam 2SE, the Questyle M12 is very similar.

One end of the M12 sports a USB type-C port while the other has a 3.5mm single ended jack for your headphones. The top panel of the unit has 2 LEDs positioned on either side of the jack; one is used to indicate high/low gain, and the other to indicate PCM, DSD, or MQA being utilized.

While none of that sounds very different than most Dongle DACs current available, like most products from Questyle — the secret sauce is on the inside.

A Karate Man Bleeds on the Inside

The Questyle M12 uses an ESS9281AC DAC at its core. The 9281AC is a system on a chip designed for portable audio use and contains a USB input controller, a DAC roughly equal to the 9802Q2M chip, a 2V headphone amplifier, and most of the supporting cast to handle all the audio functions a smartphone or other portable audio device might need.  

Several recent dongles have adopted this chip as it makes it simple to build a very compact unit without a lot of additional circuitry. Questyle uses most of the chip’s functions but bypasses the headphone amplifier in preference for their own current design. Questyle has been utilizing current driven amplification in its desktop headphone amplifiers and its implementation in a portable Dongle DAC is unique.

The differences in current mode amplification and voltage mode amplification really have to do with the limits of negative feedback and current amplification is the more complicated circuit design but has advantages in both available bandwidth and available power.  

The reason for this without going into too much of a science lesson is that negative feedback in a voltage based system diminishes as frequency goes up so either there has to be a limiter or the feedback mechanism fails.  

For audio applications, frequency is often limited to 20Hz-20kHz which allows voltage mode amplification to work without issue. Current mode amplification is more commonly seen in high bandwidth applications but is seen in audio due to its lower distortion and noise when compared to similar voltage driven designs.  

This is an oversimplification of the topic but Questyle users rave about the low noise floor, low distortion when driving very difficult headphones, and exceptional clarity.

The M12 also has another trick up its sleeve; the automatic detection of the impedance of the headphone plugged into it. The M12 adjusts power output to match the impedance profile of the headphone and as a result is one of the few dongles capable of really powering the Beyerdynamic 600 (ohm) models.  

It does mean that headphones like the Fostex T50rp are the nemesis of the M12 with a low impedance but a need for high gain as it cannot be switched manually.  

I also ran into one AKG headphone that tripped the >600 ohm barrier and put the M12 into line-out mode where I lost volume control. 

This is a feature rather than a bug as it is designed to put the M12 in line-out mode if being used as a DAC/pre-amp rather than directly outputting to a headphone.  (just know that it can happen if using headphones near 600 ohms).  

Another noteworthy point, on most devices, the M12 will not be detected without a headphone connected as the detection process is part of the devices start-up routine. I’ve seen more than a few questions on forums and Facebook about QC issues that turn out to be due to not having a device plugged in.

Bugs?

I did run into a couple of genuine quality control issues but it turned out to be more the software connecting to the M12 than the M12 itself. Foobar suffers from drop-outs when using WASAPI but works well with direct sound.  

The M12 also seems to be application dependent on Android as well as I had better luck with UUAP and neutron than with Poweramp and some other players. I didn’t have any issues with Tidal or with my Apple iPhone.

Sound Quality

The biggest takeaways from listening to the M12 are that it has a near neutral tonal balance with good detail and more than enough power for most situations . The bass response is quite potent with sufficient texture and impact without sounding elevated above its overall neutral presentation.

The M12 can also deliver that degree of control across most types of music without losing its edge as the music becomes more complex and demanding of both the Dongle DAC and headphones. Not every Dongle DAC in the category is as authoritative or poised in that regard.

The midrange is very transparent sounding and well-detailed; the treble has good extension and some air at the top but stops short of being harsh. It is a relatively balanced sounding Dongle DAC with excellent resolution. I did hear a few small artifacts with some MQA-encoded tracks but I’m not entirely sure if it was the track itself or a fault with the source device.

The soundstage is reasonable in terms of its depth and width; it does lack some depth compared to the EarMen Sparrow and some of the larger and more powerful Dongle DACs available but it’s definitely acceptable in that regard. It’s definitely not the best in the category if soundstage depth and width is one of your top criteria.

The cost of all that performance is battery life and I did notice that my phone batteries did take a significant hit when using the M12 for extended listening sessions.

Conclusion

From a sonic perspective, I have nothing but praise for the Questyle M12 — but not everything when it comes to Dongle DACs is about just sound quality.

The M12 is one of the best available below $200 (perhaps even the best) but there are some operational issues to consider; It struggles with low impedance, low sensitivity models where it needs high gain but the auto-sensing forces the M12 into low gain mode.

On the other hand, if you are using high impedance headphones like the Sennhesier HD58x, HD6xx series, or even the 600 ohm Beyerdynamic models, the M12 is one of the few dongles that really deliver enough power to drive them fully.   

For low impedance, high sensitivity IEMs, it has a jet black noise floor and does a great job of not over-driving them. Within its limits and with specific headphones, the Questyle M12 is near the top of the pile at this very moment.

For more information: Questyle M12

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