The review article comes from the Korean media outlet Gamja sarada.
In this review, we are going to discuss two USB DAC products launched by Questyle - the M12i and M15i.
In this review, we are going to discuss two USB DAC products launched by Questyle - the M12i and M15i.
The main feature of these two devices is the integration of Questyle's proprietary CMA (Current Mode Amplification) technology into a compact USB DAC form factor. Questyle's engineers have put in significant effort to achieve the integration of this technology while maintaining a compact and portable design. They managed to adopt SiP (System-in-Package) packaging technology which allowed them to successfully integrate the complex components used for current amplification.
Founded in 2012 in China, Questyle quickly made a significant impact on the audio market with the introduction of its first amplifier, featuring groundbreaking "Current Mode Amplification" technology. This innovative core technology not only defines the brand's identity but also laid the foundation for its future growth.
In less than two years, Questyle's products were prominently displayed in the largest Bang & Olufsen store in the United States, marking the brand’s rapid rise and establishing it as a globally well-reconsidered company.
Questyle didn't rest on their laurels after achieving great success in the headphone amplifier market. Instead, they collaborated with leading semiconductor companies to miniaturize their CMA (Current Mode Amplification) circuitry, continuously pushing the boundaries of their technology.
Questyle, with its relentless focus on technological innovation, is now exploring new frontiers by applying its proprietary Current Mode Amplification technology to other product lines. One notable example of this effort is the QP series of DAPs (Digital Audio Players). Following this successful venture, Questyle introduces the latest additions: the M12i and M15i, which we will be discussing today.
The outer packaging of Questyle's M12i / M15i USB DAC features a very simple design.
Upon untying the ribbon and opening the packaging, the first thing you will notice is the array of manuals and the main product itself. The product specifications are conveniently listed on the back of the packaging.
The packaging and accessories of these two products are basically the same.
As you lift the lid and remove the manuals, you will find the main device securely nestled in a foam compartment at the center. Beneath the device, you will discover a Type-C to Type-C data cable and a Type-C to USB-A adapter. It's worth noting that the quality of the Type-C to Type-C cable is particularly impressive.
Although the M12i and M15i have obtained MFI certification and are compatible with Apple products, the packaging does not include a Lightning to Type-C cable. If you want to connect to devices with a Lightning interface，you need to buy a separate OTG cable.
Let's take a look at the M12i.
Among portable DAC products, the M12i is impressively compact in size. Its design is particularly striking, featuring a transparent window that allows a clear view of the internal circuit board.
For achieving a transparent design while ensuring high durability, Questyle has used a special type of strengthened glass called Kunlun Glass. This glass is well-recognized for its application in Huawei smartphones and is known for its exceptional durability.
One side features a USB-C port for data input, while the other side has a 3.5mm single-ended jack.
Let's take a look at the M15i. We can see that it is equipped with a 3.5mm single-ended jack as well as an additional 4.4mm balanced jack.
Due to the larger size of the 4.4mm balanced jack, the overall size of the M15i are slightly bigger. Nevertheless, its size remains average among portable DAC products.
Neither of the two products has a separate volume control button. However, the M15i is specifically equipped with a gain adjustment switch. This is particularly useful when connecting low-impedance headphones to the 4.4mm balanced jack.
Let's move on to the circuit board of the M12i.
Between the connectors at both ends lies an array of chipsets, with the most prominent being the ESS Sabre ES9281AC DAC chip. This low-power, high-performance quad-core DAC chip is widely used in various portable DAC products, with its performance thoroughly validated by the market.
Beneath the CMA (Current Mode Amplification) logo, you’ll find the SiP chipset, specifically developed to enable Questyle's Current Mode Amplification technology. SiP stands for System-in-Package, which refers to the integration of multiple circuit components with different functions into a single package. This technology allows for circuits to be stacked in multiple layers, facilitating overall miniaturization.
While this manufacturing approach is technically demanding and increases production costs, it enables Questyle's patented Current Mode Amplification technology to be integrated into a chip smaller than a fingernail, making the compact USB DAC form factor possible.
The M15i takes things a step further by incorporating an additional SiP amplifier chipset to achieve a fully balanced design. This is why you will find the increasingly popular 4.4mm balanced output alongside the standard 3.5mm jack.
Despite having a standalone amplifier design, Questyle’s USB DACs manage to maintain excellent control over power consumption and heat generation, perfectly aligning with the needs of portable devices.
Questyle understands that current limitations in smartphones can lead to noise and connection issues. To address this, they have integrated a TOREX power management chip, ensuring efficient performance with lower power consumption.
In practical tests, the M12i and M15i can stably drive various headphones when connected to mobile devices like Samsung or iPhone. Even during the hot summer days, the temperature of these two devices remains low, even cooler than other portable DAC products on the market.
M12i and M15i use "current (A) amplification" instead of the typical "voltage (V) amplification". Unlike "voltage amplification" which boosts voltage by regulating current, the key feature of "current amplification" is to amplify current as steadily as possible.
You may have learnt this formula in physics class: "V = I × R," which means current times resistance equals voltage. According to this formula, voltage (V) is proportional to current (I), which may lead one to believe that there is no significant difference between the two amplification methods.
In reality, some headphones may struggle to demonstrate the differences between these two amplification methods. However, the key point is that the impedance (i.e., resistance, R) of the headphones and IEM connected to the DAC often changes dynamically rather than remaining constant.
The HD600, ranked as one of the best headphones in history, is a great example of this. Although the HD600's specification sheet lists its impedance as 300Ω, if we measure its impedance by frequency, we will find that at around 100Hz, the impedance value will spike to around 550 Ω.
If we pair products like the HD600, which have a low-frequency impedance peak characteristic, with a Questyle DAC, what changes will occur?
In the frequency range where the impedance curve rises, the voltage (V) will increase, which will affect the diaphragm's displacement and volume.
In other words, we can expect to hear changes in sound in the low-frequency range, as if an equalizer has been applied according to the impedance curve.
In practice, when pairing and listening to the HD600, although the changes in sound are not as dramatic as the impedance curve suggests, one can indeed perceive that the low frequencies become thicker, and the bass resonance feels deeper.
Founded in 2012 in China, Questyle quickly made a significant impact on the audio market with the introduction of its first amplifier, featuring groundbreaking "Current Mode Amplification" technology. This innovative core technology not only defines the brand's identity but also laid the foundation for its future growth.
In less than two years, Questyle's products were prominently displayed in the largest Bang & Olufsen store in the United States, marking the brand’s rapid rise and establishing it as a globally well-reconsidered company.
Questyle didn't rest on their laurels after achieving great success in the headphone amplifier market. Instead, they collaborated with leading semiconductor companies to miniaturize their CMA (Current Mode Amplification) circuitry, continuously pushing the boundaries of their technology.
Questyle, with its relentless focus on technological innovation, is now exploring new frontiers by applying its proprietary Current Mode Amplification technology to other product lines. One notable example of this effort is the QP series of DAPs (Digital Audio Players). Following this successful venture, Questyle introduces the latest additions: the M12i and M15i, which we will be discussing today.
The outer packaging of Questyle's M12i / M15i USB DAC features a very simple design.
Upon untying the ribbon and opening the packaging, the first thing you will notice is the array of manuals and the main product itself. The product specifications are conveniently listed on the back of the packaging.
The packaging and accessories of these two products are basically the same.
As you lift the lid and remove the manuals, you will find the main device securely nestled in a foam compartment at the center. Beneath the device, you will discover a Type-C to Type-C data cable and a Type-C to USB-A adapter. It's worth noting that the quality of the Type-C to Type-C cable is particularly impressive.
Although the M12i and M15i have obtained MFI certification and are compatible with Apple products, the packaging does not include a Lightning to Type-C cable. If you want to connect to devices with a Lightning interface，you need to buy a separate OTG cable.
Let's take a look at the M12i.
Among portable DAC products, the M12i is impressively compact in size. Its design is particularly striking, featuring a transparent window that allows a clear view of the internal circuit board.
For achieving a transparent design while ensuring high durability, Questyle has used a special type of strengthened glass called Kunlun Glass. This glass is well-recognized for its application in Huawei smartphones and is known for its exceptional durability.
One side features a USB-C port for data input, while the other side has a 3.5mm single-ended jack.
Let's take a look at the M15i. We can see that it is equipped with a 3.5mm single-ended jack as well as an additional 4.4mm balanced jack.
Due to the larger size of the 4.4mm balanced jack, the overall size of the M15i are slightly bigger. Nevertheless, its size remains average among portable DAC products.
Neither of the two products has a separate volume control button. However, the M15i is specifically equipped with a gain adjustment switch. This is particularly useful when connecting low-impedance headphones to the 4.4mm balanced jack.
Let's move on to the circuit board of the M12i.
Between the connectors at both ends lies an array of chipsets, with the most prominent being the ESS Sabre ES9281AC DAC chip. This low-power, high-performance quad-core DAC chip is widely used in various portable DAC products, with its performance thoroughly validated by the market.
Beneath the CMA (Current Mode Amplification) logo, you’ll find the SiP chipset, specifically developed to enable Questyle's Current Mode Amplification technology. SiP stands for System-in-Package, which refers to the integration of multiple circuit components with different functions into a single package. This technology allows for circuits to be stacked in multiple layers, facilitating overall miniaturization.
While this manufacturing approach is technically demanding and increases production costs, it enables Questyle's patented Current Mode Amplification technology to be integrated into a chip smaller than a fingernail, making the compact USB DAC form factor possible.
The M15i takes things a step further by incorporating an additional SiP amplifier chipset to achieve a fully balanced design. This is why you will find the increasingly popular 4.4mm balanced output alongside the standard 3.5mm jack.
Despite having a standalone amplifier design, Questyle’s USB DACs manage to maintain excellent control over power consumption and heat generation, perfectly aligning with the needs of portable devices.
Questyle understands that current limitations in smartphones can lead to noise and connection issues. To address this, they have integrated a TOREX power management chip, ensuring efficient performance with lower power consumption.
In practical tests, the M12i and M15i can stably drive various headphones when connected to mobile devices like Samsung or iPhone. Even during the hot summer days, the temperature of these two devices remains low, even cooler than other portable DAC products on the market.
M12i and M15i use "current (A) amplification" instead of the typical "voltage (V) amplification". Unlike "voltage amplification" which boosts voltage by regulating current, the key feature of "current amplification" is to amplify current as steadily as possible.
You may have learnt this formula in physics class: "V = I × R," which means current times resistance equals voltage. According to this formula, voltage (V) is proportional to current (I), which may lead one to believe that there is no significant difference between the two amplification methods.
In reality, some headphones may struggle to demonstrate the differences between these two amplification methods. However, the key point is that the impedance (i.e., resistance, R) of the headphones and IEM connected to the DAC often changes dynamically rather than remaining constant.
The HD600, ranked as one of the best headphones in history, is a great example of this. Although the HD600's specification sheet lists its impedance as 300Ω, if we measure its impedance by frequency, we will find that at around 100Hz, the impedance value will spike to around 550 Ω.
If we pair products like the HD600, which have a low-frequency impedance peak characteristic, with a Questyle DAC, what changes will occur?
In the frequency range where the impedance curve rises, the voltage (V) will increase, which will affect the diaphragm's displacement and volume.
In other words, we can expect to hear changes in sound in the low-frequency range, as if an equalizer has been applied according to the impedance curve.
In practice, when pairing and listening to the HD600, although the changes in sound are not as dramatic as the impedance curve suggests, one can indeed perceive that the low frequencies become thicker, and the bass resonance feels deeper.
If you find that the bass on the HD600 or other open-back headphones is slightly lacking, the Questyle M series DACs might be the perfect match for you.
The compatibility of the M12i and M15i with IEM is also excellent. In particular, when paired with single balanced armature headphones, you will experience various changes, such as a brighter sound, making it a lot of fun to try different headphones.
Thanks to their exceptionally low distortion rates, the M12i and M15i can deliver noise-free, clear sound whether you’re using highly sensitive in-ear monitors or more demanding over-ear headphones.
With their current-driven design, the Questyle M12i and M15i integrate the unique impedance characteristics of your headphones and earphones into the sound. These DACs allow you to rediscover the charm of your familiar gear or explore the fun of finding the perfect pairing with various devices.
The phenomenon described earlier with the HD600 is a result of back electromotive force generated when the driver operates at its optimal resonant frequency. This isn’t exclusive to the HD600; in fact, a wide variety of products exhibit diverse impedance curves for different reasons, making the Questyle M series an ideal choice for audiophiles seeking precision and compatibility.
Multi-driver headphones, especially multi-dynamic driver models with crossover networks, are classic examples where impedance characteristics can cause unexpected sound changes when paired with specific products. However, for single dynamic driver (1DD) earphones or planar magnetic headphones with strong magnetic systems, the impedance characteristics are typically very flat. As a result, you may not notice significant sound differences when using these types of headphones.
Let’s talk about the compatibility of the M12i/M15i USB DAC with planar magnetic headphones.
Although the tonal changes may not be dramatic, the driving compatibility with planar headphones remains excellent.
Looking at HiFiMAN’s lineup, renowned for producing high-quality planar magnetic headphones, we observe that many of their models are classified as "low sensitivity, low impedance headphones." This means they have relatively low sensitivity and impedance values, making them challenging to drive. By calculating these parameters, we can estimate the voltage and current required to drive them effectively.
If we set the target listening volume to 110dB, the required voltage would be around 1.59Vrms, which may not seem very high. However, the real challenge lies in the required current.
Driving low sensitivity headphones demands higher power (P). According to the formula P = I × V = I × I × R, when impedance (R) decreases, the required current (I) increases significantly. Simply put, current (I) is directly proportional to power (P) and inversely proportional to impedance (R). In cases where high power is needed but impedance is low, the current demand becomes substantially greater than what standard devices can typically supply.
Given the reasons mentioned above, Questyle DACs utilizing "Current Mode Amplification" may demonstrate advantageous characteristics when driving planar magnetic headphones. However, even with current mode amplification, the M12i and M15i, as USB DACs designed for compatibility with mobile devices, have inherent power limitations. As a result, driving planar headphones through the single-ended output may present some constraints. Nevertheless, the balanced output of the M15i is expected to deliver a notably satisfying performance.
Unfortunately, Questyle has not disclosed specific output parameters based on a 32-ohm low-impedance load for the M15i. However, according to feedback from users both domestically and internationally, the M15i performs admirably when driving demanding planar headphones, offering a performance that exceeds expectations.
In a market saturated with USB DACs featuring similar chipsets and configurations, Questyle’s M12i and M15i stand out thanks to their distinctive "Current Mode Amplification" technology, setting them apart as truly unique products.
The M12i and M15i are the culmination of Questyle’s long-term commitment to "Current Mode Amplification" technology—a testament to their relentless pursuit of audio excellence. Many users who have auditioned these devices have recognized their value, and I too find myself captivated by their charm.
These products, though only the size of a thumb, truly embody the allure of "Current Mode Amplification" and exhibit a high level of execution. For those seeking flagship USB DACs with unique characteristics and impressive driving capabilities, I can wholeheartedly recommend the M12i and M15i.
The compatibility of the M12i and M15i with IEM is also excellent. In particular, when paired with single balanced armature headphones, you will experience various changes, such as a brighter sound, making it a lot of fun to try different headphones.
Thanks to their exceptionally low distortion rates, the M12i and M15i can deliver noise-free, clear sound whether you’re using highly sensitive in-ear monitors or more demanding over-ear headphones.
With their current-driven design, the Questyle M12i and M15i integrate the unique impedance characteristics of your headphones and earphones into the sound. These DACs allow you to rediscover the charm of your familiar gear or explore the fun of finding the perfect pairing with various devices.
The phenomenon described earlier with the HD600 is a result of back electromotive force generated when the driver operates at its optimal resonant frequency. This isn’t exclusive to the HD600; in fact, a wide variety of products exhibit diverse impedance curves for different reasons, making the Questyle M series an ideal choice for audiophiles seeking precision and compatibility.
Multi-driver headphones, especially multi-dynamic driver models with crossover networks, are classic examples where impedance characteristics can cause unexpected sound changes when paired with specific products. However, for single dynamic driver (1DD) earphones or planar magnetic headphones with strong magnetic systems, the impedance characteristics are typically very flat. As a result, you may not notice significant sound differences when using these types of headphones.
Let’s talk about the compatibility of the M12i/M15i USB DAC with planar magnetic headphones.
Although the tonal changes may not be dramatic, the driving compatibility with planar headphones remains excellent.
Looking at HiFiMAN’s lineup, renowned for producing high-quality planar magnetic headphones, we observe that many of their models are classified as "low sensitivity, low impedance headphones." This means they have relatively low sensitivity and impedance values, making them challenging to drive. By calculating these parameters, we can estimate the voltage and current required to drive them effectively.
If we set the target listening volume to 110dB, the required voltage would be around 1.59Vrms, which may not seem very high. However, the real challenge lies in the required current.
Driving low sensitivity headphones demands higher power (P). According to the formula P = I × V = I × I × R, when impedance (R) decreases, the required current (I) increases significantly. Simply put, current (I) is directly proportional to power (P) and inversely proportional to impedance (R). In cases where high power is needed but impedance is low, the current demand becomes substantially greater than what standard devices can typically supply.
Given the reasons mentioned above, Questyle DACs utilizing "Current Mode Amplification" may demonstrate advantageous characteristics when driving planar magnetic headphones. However, even with current mode amplification, the M12i and M15i, as USB DACs designed for compatibility with mobile devices, have inherent power limitations. As a result, driving planar headphones through the single-ended output may present some constraints. Nevertheless, the balanced output of the M15i is expected to deliver a notably satisfying performance.
Unfortunately, Questyle has not disclosed specific output parameters based on a 32-ohm low-impedance load for the M15i. However, according to feedback from users both domestically and internationally, the M15i performs admirably when driving demanding planar headphones, offering a performance that exceeds expectations.
In a market saturated with USB DACs featuring similar chipsets and configurations, Questyle’s M12i and M15i stand out thanks to their distinctive "Current Mode Amplification" technology, setting them apart as truly unique products.
The M12i and M15i are the culmination of Questyle’s long-term commitment to "Current Mode Amplification" technology—a testament to their relentless pursuit of audio excellence. Many users who have auditioned these devices have recognized their value, and I too find myself captivated by their charm.
These products, though only the size of a thumb, truly embody the allure of "Current Mode Amplification" and exhibit a high level of execution. For those seeking flagship USB DACs with unique characteristics and impressive driving capabilities, I can wholeheartedly recommend the M12i and M15i.
RudeWolf
100+ Head-Fier
- Joined
- May 29, 2011
- Posts
- 469
- Likes
- 249
50mA is a challenge?
Very good review. Very detailed.
SilicaGel
New Head-Fier
Well, I never expected to see my review translated here. What a surprise.
For those wondering - 'gamja' is 'potato' in Korean, and 'sarada' is also 'salad' in Korean.
So yeah, I'm using 'potatosalad' as a nickname over there. lol
I intended to mention it as one of the positive aspects of Current Amplification technology, but I think the analogy was a bit off, thank you for mentioning.
For those wondering - 'gamja' is 'potato' in Korean, and 'sarada' is also 'salad' in Korean.
So yeah, I'm using 'potatosalad' as a nickname over there. lol
I also think it's not really a problem anymore, as small USB DACS have become astonishingly powerful these days.
I intended to mention it as one of the positive aspects of Current Amplification technology, but I think the analogy was a bit off, thank you for mentioning.
RudeWolf
100+ Head-Fier
- Joined
- May 29, 2011
- Posts
- 469
- Likes
- 249
I think it's a decent review overall. Current mode amplification is a bit esoteric. Proponents of it claim that it lowers distortion in transducers. The problem is that most speakers and headphones are built with voltage drive in mind and hence will exhibit unusual behavior when driven by a high output impedance source. Single drivers usually will increase amplitude at self-resonance frequency (thus the bass boost). The real problems start with multi-driver IEMs where the load is much more complex and interacts with the high-impedance driver. There you will get tonal shifts from both the drivers and the filter unit.
0.966 and 1.22 is high impedance out?
(Based of gen 1, gen 2 has no published specs)
