Questyle Audio CMA400i Current Mode True DSD DAC/Preamp/Headphone Amplifier – Peer Into the Black Depths of Music

About two years ago, Questyle Audio discontinued their popular entry level desktop DAC/Amp, the Q192, in favor of their new Portable Music Server the QP1R. Since True DSD had become a focus for the company and the DAC chip employed in the Q192 did not support it, the Q192 was no longer representative of Questyle Audio’s direction. Instead, they adopted a top down approach to new products, beginning with the well received CMA800i DAC/ Preamp/Amp, a combination of their then flagship CAS192D True DSD DAC and their CMA800R Current Mode Headphone Amplifier in a single case sharing a single power supply. They then released their even more popular CMA600i DAC/ Preamp/Amp, a scaled down version of the CMA800i, with a less expensive DAC and a smaller power supply, but offering more gain and a balanced output (see Eric’s review here). They followed this up with their “Gold Stack” Reference System which I reviewed last year (see the review here). Now they have released a new entry level desktop DAC/ Preamp/Headphone Amplifier the CMA400i, and I would not fall very short to call it state of the art.

The Technology:

I would be remiss in reviewing a Questyle product without some time spent on the technology, as utilizing new and exclusive technologies is their forte. In fact, they hold at least eight patents, the first being their application of Trans Linear Theory for what they call “Current Mode Amplification”.

Questyle Audio is not the first company to use Current Mode Amplification, several ultra high end amplifier companies such as Halcro and Krell have used Current Mode Transmission in their top model amplifiers and preamplifiers for a while now, and most microwave communication is dependent on Current Mode Amplification as Voltage Mode Amplification is not capable of sufficient bandwidth, but what is completely unique to Questyle is their application of Current Mode Amplification, completely eliminating the basic issues of Current Mode Amplification.

The primary drawback to Current Mode Amplification is that it requires a fixed impedance load, which makes it entirely inappropriate for use with speakers (or headphones) which are a dynamic impedance load. To deal with this, Questyle developed a multi-stage amplifier topology. The first stage converts the incoming Voltage Mode signal to Current Mode (in Voltage Mode the signal is created by modulating voltage, whereas in Current Mode, current is modulated). The second stage is a fully discrete pure Class A amplifier operating in Current Mode, all signal amplification takes place here (Gain). The third stage is the negative feedback loop also operating in Current Mode (the negative feedback loop is employed to improve stability, IE: limit Total Harmonic Distortion [THD]). The final stage converts the signal from Current Mode back to Voltage Mode thus making the amplifier compatible with dynamic impedance loads. I hear you saying, “Well that’s fine and all, but what’s the benefit?” The benefit is speed. Questyle Current Mode Amplifiers have a linear bandwidth (linear bandwidth refers to the frequency response at all power levels from 0 to full rated power) in excess of 500 kHz, and by having the negative feedback loop operate in Current Mode, they produce no Transient Intermodulation Distortion (TIMD – that slight harshness and metallic sound associated with solid state amplifiers).

At this point I would like to comment on the deceptiveness of power ratings. While the Questyle Audio CMA400i has a fairly respectable power output of almost a Watt at 32Ω, due the Current Mode Amplifier, it is actually equivalent to amplifiers of much higher outputs using other topologies. “How is that,” you ask? Well power is the product of Voltage and Current, essentially Voltage is pressure and Current is flow, and it is the Current that does the heavy lifting, since Current Mode Amplifiers operate in the Current domain, they tend to be Current heavy. To give an analogy that might be easier to understand, in an engine, Horsepower is the product of Torque (twisting force) and RPM (how fast the motor is turning). Torque is the equivalent of Current and RPM is the equivalent of Voltage. As any gear head can tell you, if you have two vehicles with all else being identical, it is the vehicle with more Torque that has the greater pulling power. Back in the world of audio, it is Current that determines how fast a speaker driver starts and stops, which determines how much detail you have and how accurate, especially in the low frequencies, which require much more Current to reproduce.

Questyle Audio, never afraid to show their build quality and use of top quality components including a custom made NORATEL Toroidal Transformer, Nichicon FG capacitors in the power supply, WIMA capacitors in the audio chain and DALE military resistors

True DSD is an implementation that involves bit-streaming DSD from the source to the DAC chip to be decoded in its native format without encoding into PCM packets (DoP) and without the use of filters (including the standard low pass filter, giving Questyle DACs a bandwidth of about 100kHz with DSD64), bypassing all digital signal processing including volume control.

The Experience:

I received a prototype Questyle Audio CMA400i a couple of weeks ago to conduct an IEM review. I know you’re thinking, “How so?” Well this is the most exciting thing about the CMA400i, it was designed from the ground up with IEMs in mind, and goes so far as to be the first desktop DAC/Amp to include a 2.5mm Balanced output. It also has user accessible gain switches on the bottom for use with IEMs. Beyond that, with the press of a button it can be used as a straight DAC, with both single ended and balanced outputs, or as DAC/Preamp for use in a two channel system.

The CMA400i was the best match for the Periodic Be IEMs of all the sources I tested with them, taking full advantage of the Be’s extended high frequencies without being painful or fatiguing, while providing strong, well controlled bass.

Starting with the MrSpeakers ETHER C Flows single ended, in the low gain setting, listening to “And You And I” (Yes – Close to the Edge – DSD), the inky black silence of the noise floor was breath taking, allowing me to hear a synthesizer subsonic sweep that I had never noticed before in the thousands of times I had used that track for reference. The dynamic range was stunning, and I was able to achieve plenty of volume in the low gain mode single ended (I never came close to full volume).

Switching to balanced, with the same track, the increase in dynamic range was palpable. The soundstage was huge, giving the song that epic presentation it truly deserved. The levels of detail cannot be overstated, especially in the low frequencies elucidating the many layers of musical instruments used in the recording.

Returning to IEMs, I broke out the Noble Katanas, it was transcendent. I would point out that this was the first time I listened through a desktop unit where I didn’t hear noticeable levels of gain noise, in fact it was dead silent at normal listening levels with no signal. I purposely waited until I was listening through the Katana’s before having my usual session with “The Firebird Suite” (Eiji Oue & Minnesota Orchestra – DSD, Robert Shaw & Atlanta Symphony Orchestra – 24/96kHz vinyl rip) as I anticipated this being the first time I would fully experience what the Nobles are capable of and I wasn’t disappointed. For the first time, I felt the same chills listening to the Eiji recording that I normally associate with the Shaw performance. Not only was the soundstage three dimensional and large, the instrument placement laser pointer sharp, the dynamics were as close to real life, as I have heard. The tonal balance was exceptional, making it easy to separate the oboe from the French horn from the clarinet from the bassoon, the violin from the viola. There was a breathy flute overlayed over the oboe that simply wasn’t there before. And the tympanis, fast, impactful and dynamic, each pulse clearly delineated, with the triangle ringing a sharp counterpoint.

Questyle Audio’s Bruce Ball proudly displays the production sample of the CMA400i

To judge the musicality of the midrange, I put on Sinéad O’Connor’s “Just Like U Said It Would B” (The Lion and the Cobra – 16/44.1kHz), not only is her voice heart wrenching, it is a bit strident bordering on harsh. All of the emotion was there, clear without veil or syrup, but totally musical, edge without harsh or distortion.

Exploring the CMA400i’s performance with less expensive gear, I popped in the 1MORE Dual Driver IEMs and cued up “Non Mi Lasciare” performed by Dario Baldan Bembo (16/44.1kHz). The piano was rich and powerful, the bass deep, resonant and pervasive. As for the operatic vocals they were mystical, performed in a vast empty hall.

As a final experiment I connected the balanced preamp out to my desktop rig to see how the CMA400i fares as a DAC. While not as “Analog” sounding as my reference DAC (which sells for over double the price), the sound was spectacular, exhibiting amazing bass extension and control, as well as, a smooth clarity that bests most DACs I’ve tried, as evidenced playing Jimi Hendrix’s cover of “Born Under a Bad Sign” (DSD128).

The Wrap Up:

The Questyle Audio CMA400i is one of the most versatile products I have tested. It operates equally well with IEMs and hard to drive full size Cans. While the ETHER C Flows may not be the most difficult to drive headphone, it is a planar magnetic which do like a little bit of current. In the high gain mode using the balanced output I would be surprised to find many headphones that the CMA400i can’t drive easily and well. At its price point, I can heartily recommend it as a low cost high performance DAC, though you may well discover that its amp outperforms whatever amplifier you were planning on matching it up to. And for those of you who wish to enter the wonderful world of two channel audio, simply add a pair of quality amplified speakers and you’re ready to go.

As for sound quality, it leaves little to be desired, it has excellent tonal balance and exemplary bandwidth and detail. The low frequency extension and control is a must hear to believe proposition. While it does not veil or sweeten the mid range, neither does it add anything to it, meaning it has a musicality that makes even listening to headphones that fall out on the bright or harsh side can be a pleasant and eye opening experience. While I attribute a great deal of the performance of the DAC to the amplifier section, and the wonderful ears of the designers at Questyle, you would be hard pressed to find one that has greater detail and low frequency performance.

Price: $799 USD

Specifications:

Pre-amplifier and DAC Section

  • THD+N: RCA:< 0.0009%; XLR:< 0.0009% – SNR: RCA: >110dB; XLR: >113dB (non-weighting)
  • USB Type B Input:

44.1K-384K/16-32Bit PCM and DSD native, DSD64 / 128 / 256

  • Digital Interface:

SPDIF input and output, OPT input;

Support 44.1K-192K / 24Bit PCM

Headphone Amplifier Section

  • Output Interface:

A 6.35mm standard headphone jack

A 4-PIN full-balanced headphone jack

A 2.5mm full-balanced headphone jack

  • Max Output Power (Po):

106mW@300Ω; 980mW@32Ω (normal headphone jack)

418mW@300Ω; 3920mW@32Ω (balanced headphone jack)

  • THD+N:

0.0013%@1kHz, Po=100mW, 300Ω

0.0016%@1kHz, Po=50mW, 32Ω

  • Frequency Response:

DC-100kHz (+0, -0.7dB); DC-600kHz (+0, -3dB)

Chassis

  • Finish: Black
  • Chassis Materials: special CNC tooled Aluminum
  • Dimension:279mm[W]×189mm[D]×55mm[H]
  • Weight:84.65oz (2.4kg)
  • Working Status: Pure Class A
  • Voltage : 100-120V or 220-230V, switchable
  • Power Consumption:17W

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Gary Alan Barker

Gary Alan Barker is a writer who has been a member of the Audio Industry since 1978, having acted as technical writer for several high-end audio companies, and been an electronics hobbyist since 1960. He has also been a musician and writer since the mid 1960s.

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REPLY
  • Saleh Munir
  • 2017-08-15 02:05:00
  • Hi Gary, many thanks for your response and the time you spent to mention all these details. I highly appreciate it! couldn't find the reply here on this page, so I started a new comment. I think I feel more comfortable with the cma400i now. as mentioned, I can't try it before I buy it, but moon audio offer 14 days return option with 10% restocking fee, fair enough. will update if I end up buying it in the next couple of weeks! thanks again.
  • Reply


  • Gary Alan Barker
  • 2017-08-14 21:51:00
  • The HD800 are in my experience one of the hardest headphones to drive properly. The Questyle CMA800R was designed specifically to drive the HD800 and I felt they only truly came alive when running two CMA800Rs in dual mono. That being said, a couple of weeks ago I had the opportunity to listen to the HD800 on both the CMA600i and the CMA400i, and I felt the CMA400i did an admirable job and was perfectly acceptable. On the other hand, the CMA600i will sound better with them, and the CMA800i better still, and the CMA800R better then that, with the dual mono configuration only being outperformed by the "Gold Stack" Reference system, but like all high-end audio, the returns become less and less as the price goes up. The fundamental difference between the CMA400i and the CMA600i is one of power supply. A larger power supply means more dynamic headroom which exhibits itself in terms of tighter more controlled and more dynamic bass. It will also give you a little more detail and a slightly more musical midrange as a result of that improved control. (Moving to the upper products you also have a change of DAC which makes a notable difference in the sound, and the Golden units have completely different and unique circuit boards, which effects everything) At the same event where I listened to the two using the HD800, another gentleman had a pair of HD800 S that he did extensive comparison tests with the two and eventually chose the CMA600i, though I believe overall volume was also a consideration in his listening tests. Music can also be a consideration, if you listen to a lot of bass heavy music then you may need the CMA600i. And of course price is a consideration, there is a significant jump between the two. I would really recommend listening to the CMA400i and see if it meets your needs, I should also point out that you will need a balanced cable for the HD800 S (the CMA400i has 4 times the power output in balanced). As to the Woo Fireflys, they are probably closest to the CMA400i, but that being said, there is a significant difference between the sound of a tube amp and a current mode amp, especially depending on the tubes you are using. While they are trying to achieve the same results (the elimination of TIMD) they do it in a completely different way. Essentially a current mode eliminates TIMD by offering a bandwidth that exceeds the production of TIMD pushing it well outside the audible spectrum (in the case of the CMA400i about 500 kHz) while a tube amp eliminates TIMD by having a slew rate that is too slow to reproduce it. So the CMA400i will be a lot more neutral and natural sounding with deeper and more controlled bass. While the CMA400i is very musical it will not cover up or de-emphasize flaws in the upper midrange of your source material. Given the right tubes, a tube amp can be very magical, they have a very honeyed midrange and highs, though they can often lack bass, they can also take the edge of a headphone like the HD800 S, especially with low resolution sources. So again, while I heartily recommend the CMA400i, I also recommend listening before you buy, if at all possible, if not, buy from a reliable dealer who will allow a reasonable audition period.
  • Reply


  • Saleh Munir
  • 2017-08-11 07:01:00
  • Hi Gary, I'm quiet a beginner in personal audio world, my apologies if any of my questions seemed naive. i was wonder if its a prediction or if you have actually tried the CMA400i with an HD800 S and found that it doesn't have enough power? I was about to buy it instead of the CMA600i (CMA400i has lower price and I don't need any more features than what it has!) but your comments here kind of stopped me. unfortunately I cant try before I buy as you recommended, and not much reviews out there yet. I do have a Woo WA7 tube amp gen2 now which is awesome, but I'm really keen on getting a fully balanced amp, especially that I got that expensive balanced cable already when I bought my HD800 S and I keep reading about the advantages of using it for the HD800s. after some endless search, I'm convinced to go with questyle. the question is which one of these two. another question that I have failed to find an answer for, is how these amps fair compared to my Woo WA7 tube amp .have you tried it with an HD800 S? I wonder if I would I be getting "better" over all sound if I end up buy either the CMA600i /CMA400i.
  • Reply


  • PhotoNatura
  • 2017-08-08 09:37:00
  • Hi! Im assuming the cma400i will be enough to drive phones like the HD650 properly? At least in balanced operation?
  • Reply


  • Steve Assante
  • 2017-08-07 15:24:00
  • I would likely purchase the 400i in a "heartbeat" except for it's significant omission: that being that it lacks analog inputs for my Metrum Hex DAC! This appears to have the finesse that I'm looking for to compliment the Hex. I suppose I'll have to find a deal on the 600i (Though I'm open to suggestions for other Class A ,low gain,low distortion headphone amps.; Any thoughts on the Meier amps?)
  • Reply


  • Proghead
  • 2017-07-19 13:36:00
  • Thanks for your answer.
  • Reply


  • Gary Alan Barker
  • 2017-07-18 13:45:00
  • Hi, sorry about the delayed response, Disqus is not very good at notifying me of messages. Essentially it is a question of which headphone you're going to use, the 600i has a much heavier power supply so it will perform better with hard to drive headphones like the HD800 or the Abyss then you'll want to go with the 600i on the other hand, if you want to drive IEMs the 400i is the way to go because of the gain switches. Both amps use the same DAC and amplifier design so they pretty much sound the same, though the 400i has a lower noise floor for high efficiency headphones due to the gain switches.
  • Reply


  • Proghead
  • 2017-06-30 12:53:00
  • Hi, could you tell more please about sound differences between 400i and 600i as I see, you reviewed them both. Is 600i much better, or do they sound similar? Thanks.
  • Reply


  • Joshua
  • 2017-06-08 11:42:00
  • Good to know, thanks again! Luckily my Sig Pros are modded for balanced cables. ;)
  • Reply


  • Gary Alan Barker
  • 2017-06-07 01:32:00
  • The issue with the 800i was one of gain as opposed to power, I have run both the Ultrasone Signature Pro and the ZMFs (don't know which model, but they are all based on the same driver) on my QP1 so the 400i should do fine as it has about 3 times as much power (almost 10 times in balanced) though you may need to use the high gain setting. The 800i uses the Wolfson DAC chip and the 600i and 400i use the same AKM chip. The main difference between the 400i and the 600i is the power supply and the gain switches on the 400i. The power supply difference should mostly effect dynamic headroom, which I don't think will be a problem with the headphones you are using (if you were using HD800s or Abysses then I'd say go with the 600i). If you are able to run in the low gain which might not be a problem if you use balanced cables you will probably have a larger sound stage with the 400i due to the lower noise floor. The Wolfson is a little more analog sounding, but the AKM has more detail which means a larger sound stage. I would recommend going with balanced cables as it does open everything up a bit.
  • Reply


  • Joshua
  • 2017-06-06 17:41:00
  • Thanks for the reply! One of my main headphones is the Ultrasone Signature Pro, and I will say it did not have very much room to move the pot on the 800i. My other main set is the ZMF Blackwood, which is obviously a little greedier, but both benefit from some extra power behind the signal. It kind of sounds to me from your description that the 800i is further apart from the other models than the 400i/600i are from each other, does that sound about right? I think realistically the 400i would be a better choice for the office desk, even though I would definitely appreciate the extra juice. One last thing... Do you think soundstage is relatively comparable between the three models? Or does the power supply make a big difference in that department? Thanks again, I appreciate it!
  • Reply


  • Gary Alan Barker
  • 2017-06-06 16:57:00
  • The DAC in the 800i is a little more analog sounding but is limited to 24/192kHz or DSD64. While the 800i has a larger power supply giving more dynamic headroom, the gain is less than the 600i (or the 800R upon which it is based) meaning the maximum volume is a bit less. Both the 400i and the 600i have balanced outputs giving them almost 4 times as much output as the 800i (when using the balanced output). And finally the 400i has a smaller power supply than the 600i meaning less dynamic headroom and a little less overall power. I meant to do some direct comparisons at LAAS but ran out of time. It really comes down to what you are using for headphones. If you are using IEM's or really efficient headphones then the 400i would be the unit of choice, though I do need to go back and listen to the 800i again, because I haven't tested it with IEMs. If you have really hard to drive headphones like the HD800s, then you probably want to listen before making a decision. My guess is that the 400i has plenty of power in high gain with the balanced out (almost 1/2 a watt with the HD800s at 300Ω, and almost 4 watts for most planars).
  • Reply


  • Joshua
  • 2017-06-06 14:51:00
  • Nice! Some time ago I had the privilege of testing the 800i and decided on the spot it would be my next upgrade. I never got the chance, and since then they've released the 600i (which I haven't heard) and now the 400i. Having heard the two "senior" models, how would you say this unit compares? Which one hits the "sweet spot" in terms of cost v. value? The 400i seems like it would be a great option for my office.
  • Reply


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