xDuoo MT-602 Tube Class-A Headphone Amplifier

xDuoo MT-602 Tube Headphone Amp - Freak Trickster

MT-602 is a headphone amplifier with tubes on a budget, priced at 100 USD, and it comes with two 6J1 Tubes, runs in class A, and will be compared to JDS Labs Atom AMP+, Soundavo HP-1 DAC-AMP, and xDuoo TA-10 Headphone AMP, also with tubes.

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Introduction





xDuoo generally does not fail, but this time around they made a rather odd device. It goes to show that there is an actual limit to how much you can squeeze from a low price, and how much you can optimise things inside, before you run into certain issues. Chifi has always been my passion, and will stay a passion, as almost 70% of the awesome stuff I review is from China, but being the cheapest product out there is not always the purpose and sometimes I wish companies would invest more in the final product rather than adding every single feature possible for it. Basically, refinement goes a long way if you want to get the best product you can.





It should be noted that I have absolutely no affiliation with xDuoo or XTENIK. I'd like to thank XTENIK for providing the sample for this review. This review reflects my personal experience with xDuoo MT-602. Every opinion expressed is mine and I stand by it, the purpose of this review is to help those interested in xDuoo MT-602 find their next music companion.





Packaging





First things first, let's get the packaging out of the way:

We get the Amp, and the power delivery. Mine came from Europe, and while the cables are basic, they should be able to support full Class A mode which is how MT-602 Operates, at least judging from the paperwork.











Build Quality/Aesthetics/Functionality





The design is very basic, and made to look flashy above be useful, as I discovered that there are LED Lights beneath the tubes. This means that it is made to look impressive, at least. The overall design is clean, good quality of finishes, typical of xDuoo. There is one RCA input, and one RCA output, for using it as a Preamp. There are two headphone outputs, one in 6.3mm, and one in 3.5mm. There is a volume wheel, and even an AUX Input in 3.5mm, so you can easily connect your smartphone or DAP to MT602.

The overall device has many holes for breathing, but it doesn't get that hot, and it is clear that the company tried to make it look like a replica of a larger headphone amplifier, like APR204 from Qualtion and Audio Hungary. The unit is somewhat heavy, and feels quite nice to the touch, plus the power input is 12V DC, so you can even use some of the power deliveries from iFi, those with mega bells and whistles for a more quiet operation.





Whether they will help or not depends on how noisy your block is, and while for me using an alternative DC converter did not change the sound much, everything is possible if you already live in a really bad area electrically.





The Amplifier waits some time before powering up, so don't turn it loud, or you may blow your ears and your headphones. Especially if you're using IEMs. If the source is at max, it is extremely loud, and at almost half it is already unbearable with HIFIMAN Sundara. This being said, they are not really properly driven, and the bass is a bit slow and lacking. There is some channel imbalance at the beginning of the volume turn, so if you have a DAC with no volume control, this will become noticeable.

I would not use it for IEMs eithert, as the sound is too noisy. With IEMs, with the sound turned off, the volume wheel at absolute maximum off, you can already hear some music, so the circuit is not insulated properly. If you ever imagined that this is possible, if you knock on the unit with your fingernail, while having IEMs, the noise is passed to the IEMs. This is the very first Amplifier that does this for me officially. The sound is always a few dB louder on my right ear than on my left ear, much easier to notice with IEMs than headphones.











Sound Quality





Regardless whether you're using IEMs or headphones, it has a very stable signature, and this remains the same regardless whether the AMP had time to warm up or not. The sound is warm in the mids, with a rolled off bass that lacks substance, and with a somewhat harsh bright treble with good energy. The soundstage is really good, holographic, while instrument separation is decent. All textures have a tube sound modulation to them and have a somewhat vibrato part added by the Tube Preamp. In fact, this is something to consider, but this is not a Full Class A Tube AMP, but a Class A Hybrid Solid State AMP with tube Preamps, at least from what xDuoo writes on their website.

The bass is the part that I am not enthusiastic about the most. At low volumes, it has a rolled off presentation with the sub bass having to suffer a bit, even with Basshead IEMs like Wave, and Xelento. In fact, with almost all IEMs, the sound ends up being bright, but this does not improve with HIFIMAN Sundara, which are a bit bright and rolled off in the bass with MT-602. This changes a bit with the DAC, and it sounds better on the RCA input, than it does on the Aux Input, especially if you don't have a DAC with a Line Out. At medium to high volumes, the bass is rounded more nicely, with good overall clarity and impact, although at maximum and near maximum it tends to become a bit boomy.





The midrange is sweet, warm, and somewhat distorted by the tube, which seems to always apply a pretty high gain. Turning the DAC at a lower volume and the MT-602 loud seems to provide a somewhat clearer sound, which means that it may not be expecting a full blown 2V DAC, or that my DACs are sending more than 2V. The midrange has a nice soundstage in width, but it is not overly deep. Overa,, the detail is excellent for the price, and the sound is a bit more neutral than with the JDS AMP+.





Voicing is a bit odd, with somewhat thinner male voices, and natural female voices. We get a somewhat harsh treble presentation where it exists, but the treble also rolls off in the highest octaves, especially at high volumes. So we have two situations, where we go with a DAC at high volume and it sounds bright and harsh, and if we go with the AMP at max and the DAC at lower volumes, we get a more natural, smoother, fuller sound but which is rolled off in the treble, a bit in the bass too, and which has a somewhat harsh treble presentation. The sound works well for metal, rock, and EDM, but not for Pop, Classical, or Jazz.











Comparisons





Given that MT-602 is a 6J1 Tube AMP or rather Hybrid AMP, I decided to compare it to three devices, all different. Those include JDS Labs Atom AMP+, Soundavo HP-1 DAC/AMP, and xDuoo TA-10, which is another product also made by xDuoo.

xDuoo MT-602 vs Soundavo HP-1 DAC/AMP (100 USD vs 130 USD) - Well, for 30 USD more you can get a DAC too, which increases the value of HP-1 considerably. It also does not suffer from any of the issues that the MT-602 has, but if you're into driving a HD800 from just 100 USD, then the MT-602 has considerably more driving power, so it surely will have its fans. The main problem is that those power will be hard to control unless you have a DAC with variable volume, but then, HP-1 has a more granular control, does not have microphonics, and I recommend spending 30 USD more on a DAC/AMP that may prove to be useful for longer, especially since MT602 will need the tubes replaced eventually, costing more along the way.





xDuoo MT-602 vs JDS Labs Atom AMP+ (100 USD vs 100 USD) - Cent for cent, those two amplifiers show that if you're in the entry-level price range, going for full solid state may be a good idea. AMP+ has a more coherent sound, has more control over the sound, and generally does not suffer from any of the issues that MT-602 has. The worst part about this comparison is that despite it being solid state, AMP+ has more of that warmer, analogic sound magic, than MT-602 which is a hybrid design and has actual tubes there, only to add some distortions.





xDuoo MT-602 vs xDuoo TA-10 DAC / Tube Amplifier (100 USD vs 290 USD) - This is an excellent example of what xDuoo can do if you're ready to spend on some of their better DAC/AMPs. It is three times the price, but you get actual tubes, a good DAC performance, and what an entry-level Tube AMP is supposed to do, offer a smoother, more liquid and fun experience. Honestly, this is the most affordable Tube AMP I know at this point that is worth the effort of having tubes in your system, and I do want to open a challenge to all audio companies, for someone to make something more affordable than TA 10 that will convince me you can make tubes on a budget.











Value and Conclusion





Although we're used to seeing good value from xDuoo, this one is will cut it for most folks who just want a nice tube AMP for low cost, but for me it feels a lot like it is just a gimmick AMP made for those who never had contact with proper audiophile AMPs or DACs. Having LED lights below the Tubes, having microphonics in the AMP, having no flexible gain function despite the extremely loud output, are all issues that someone who has any decent experience with audio will notice. On the other hand, if you're a beginner, it may prove to be a fun trip, the sound is not bad at all, and the device itself works just fine for most folks.

The sound has two very different flavors, depending on whether your DAC has volume, and if you can change the volume, or if you're locked at maximum volume from the DAC at all times. If you're locked at full DAC volume, then you probably won't have the best sound, as MT-602 is quite bright and lacks body at can be shouty at low volumes, while if you do have DAC volume, you need to play with the volume of the two, as if you turn MT-602 at max and leave all volume control from the DAC, you'll get a thicker, more lush sound, but which lacks treble and can sound uncontrolled and modulated at times.

At the end of today's review, I don't hate the MT-602, it is a fun Amplifier if you want something to play with, it is well made and won't burn your headphones, but I honestly feel that it won't give the best impression of what to expect from tube tech and xDuoo made better Tube AMPs, so maybe don't try to get tube if you want to stay budget, there are good solid state options even in the entry-level range.

MT-602 is not my first encounter with the Xduoo brand, which belongs to a TA-05 model. But just like the first time around I'm again having a hybrid tube headphone amplifier on the bench.

Build and Connectivity​

xDuoo MT-602’s design took a new turn compared to TA-05. First of all, it’s smaller, packed in a sand-blasted grey aluminum body. Except for the protruding tubes on the upper side, the red volume knob also makes sure the look feels fresh and modern. I’m usually not a fan of punchy bright colors but for some reason, it looks just right in this case, especially while it’s working and tubes are glowing.

On the back panel, we find two pairs of RCA outputs. One is reserved for line input while the other one is a variable pre-amp output. So yes, you can use this little thing as a small tube preamp too. It’s power with 12V DC and the laptop-sized brick is provided in the box. The front panel hosts a power switch, volume knob, and two headphones outputs, a smaller 3.5 mm one, and a bigger 6.3 mm. A little bit unexpectedly, there’s another auxiliary 3.5 mm input in the corner too. You’ll surely not hear me complain about connectivity here.

Construction​

As already mentioned, xDuoo MT-602 is a hybrid amplifier. This means that tubes are used in a pre-amp stage while class A transistors provide power and grunt in the power-amp section. This is a scheme many products revert to trying to capture the soft and natural presentation of tubes, but without losing the power and control of a solid-state solution. That said, xDuoo claims a power of 1300 mW into 32 Ohms, with 15 dB gain, saying it’s suitable for headphones ranging from 16 to 600 Ohms. Looks promising on paper, but let’s see who it behaves in actual use.

Sound​

So let’s get this out of the way first – does Xduoo MT-602 offers a warmer sound signature, as you might expect from a device with glowing orange tubes protruding from it? Yes, it does, but only to some extent, limited to a certain part of the frequency spectrum.

The Bass region is weighty and voluminous. When mass and boldness in lower registers are needed, this amp will provide. The bassline is not noticeably slow and sluggish, but it is also not the quickest one either. Pleasantly rounded is the description that comes to mind. Great thing is that texture was not sacrificed in the process. Vibrating bass strings sound like vibrating strings and not as a faceless sweet mass. This praise-worthy texture retrieval continues over the midrange section too. The upper midrange is actually the part responsible for that is open and textured sound. Because of it, listening to a saxophone, for example, is a joy. We get both bold instrument body and raspy airy texture on top of it. If anything, that whole upper midrange part is slightly more pronounced than I’d consider perfectly neutral. Luckily, it’s done in moderation and not overcooked to the point to become harsh or picky in any way. The highest region is again very clear and resolving. If you have hoped for a sweet and roll-off treble response, you’ll have to look elsewhere.

So tonally, I really liked this little hybrid amplifier, but what about other things? Dynamics are just fine, nothing to complain about, but also nothing to write home about. This is not a heavy-hitting kind of amplifier, it’s more the type of listener that appreciates smooth sailing. Sound-staging on the other hand is as good as it gets at this price point. There’s a decent sense of width, but not much depth and three-dimensionality though. Layering is quite capable with enough air around instruments.

Pairing​

This section will be short as xDuoo MT-602 possess enough power to drive almost anything that makes any sense pairing with budget amplifiers (yes, I’m talking to you guys that are using LCD-3 paired with fifteen times cheaper amps – stop doing that, it’s not appropriate sound quality wise first and foremost). Tonally, it’s open and bright, not too much so it shouldn’t be a problem for any headphones that are not overly bright (the ones with huge and wide hills in the upper midrange part of the frequency response).

If used with sensitive in-ears, MT-602 will produce noticeable static background noise. Also, the volume knob offers louse volume control resolution and things become too loud too quickly. With that, I’ll conclude that this is a big cans amplifier, not suitable for sensitive in-ears.

Comparisons​

xDuoo TA-05 is also a hybrid tube/class A transistors amplifier but with clearly different tuning. Its bass is even more voluminous, mid-bass and midrange are warmer and with more bloom, while the highest frequencies are tamer and sweeter. It sounds as warm, bloomy, and sweet as someone could wish for if you’re after that kind of tuning. MT-602 on the other hand is more neutrally tuned, reveals more texture, and it’s brighter up top. Which one is better? Well, you’ll have to decide that one for yourself. I do prefer MT-602 but you might feel differently.

Topping L30 is a typical solid-state amplifier. It sounds clean, fast, and precise. Bass punch is decent, edges possess good energy. It sounds cleaner than MT-602. On the other hand, tone timbre and texture are not that pronounced. In that department, MT-602 has a slight lead to my ears. No matter how many times I went back and forth I couldn’t really decide on a clear winner here. It boils down to your taste and choice of music I suppose. If slow music with raspy vocals, saxophones, and other acoustic instruments is what you’re listening to most of the time, I’d give a slight edge to MT-602. If faster-paced tracks are your thing, you might appreciate a slightly punchier bass-line and more muscly presentation of the L30.

L30 is also dead silent even with sensitive in-ears so there’s that too.

Conclusion​

To come clean, I expected yet another very warm and sweet-sounding amp, but xDuoo went in a different direction this time and I do believe it’ll pay off. I like this compact styling more than the old, vintage, and chunky one too. The price to performance ratio is great and if you don’t plan to use it with in-ears, and you find described voicing appealing, I can’t think of anything particular that should prevent you from seriously considering xDuoo MT-602 as your headphone driver.

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My website with all the other reviews: https://iiwireviews.com/

Thanks to HiFiGo for sending it for the review: https://bit.ly/3eUJLCk

My video review:

disclaimer: This review was originally posted to my blog on 2/12 but I decided to post it here after my images started showing up in other reviews of it. The MT-602 was provided for the purpose of this review and the tube rolling article by Xduoo Audio. I have no financial interest in Xduoo or any of its distributors, nor did I receive any compensation beyond the product itself for this review. If you have an interest in purchasing any of the Xduoo amplifiers I have recently written about, I suggest you check out Xduoo’s website directly as they now offer direct sales. You can also follow them on Facebook for more information.


Unboxing / Packaging:

The packaging of the MT-602 is a new style for Xduoo with a very western retail look to the box. The front has the line drawing of the amp while the reverse has company info and some suggested uses but does not have even basic specs. Lifting the top of the box reveals the manual and then a couple of blocks of heavy foam. The top most block serves to protect the pre-installed tubes, while the lower block protects the 601 itself. Beneath the unit and foam protection is a box containing the power supply cable. One thing worth noting, if you get the MT-601 and 602 both like I did, the power supplies look identical, have the same sized barrel connector so will physically interchange, but are not cross-compatible as the 602 uses a 12V power supply while the 601 uses a 24V supply. Close inspection of the box on the power supply does show that the only difference in the two (externally) is the voltage label. With these in black lettering on a black surface they do not immediately leap out so marking them in some easily seen way as you unbox them may be a wise plan to keep from having problems later.





Build/Fit:

The case is anodized aluminum in a matte gray with removable end plates and rear plate. To remove the internals for cleaning or repair, only the rear plate needs to be removed as the internals no not attach to either side plate. The top of the case is vented well around the tube and the side plates also have a pattern of vents showing the Xduoo X. A pair of 6AK5 type tubes are used and protrude only about .5 inches above the top surface. Inputs are a 3.5mm jack on the right front and a pair of RCA jacks on the rear. Outputs are a 6.3mm single ended output (a 6.3 to 3.5 adapter is provided) and a 3.5mm output on the front face, and a line out provided by a pair of RCA jacks on the rear of the unit. The line-out is volume controlled so the unit can be used to introduce some tube coloration and volume control to powered monitors. The 3.5s are clearly labeled as phone and aux in respectively so shouldn’t be easy to confuse. This is purely an amplifier so no usb, optical, or coax connectors are needed and the only other features not covered yet are a large red volume knob centered immediately in front of the tubes and a 12V DC input on the rear of the unit. Overall the unit stands a little over 1.5 inches tall (excluding the tube) , about 5 inches long and a little over 3 inches deep. The unit weighs slightly less than a lbs as well so is quite compact and comparable to the Schiit Magni or Modi in size and heft. The 602 is very slightly heavier than its 601 counterpart but for all practical purposes these two are identical in size and heft.




Internals:

The MT-602 uses a pair of 6AK5 tubes as the pre-amp followed by four D882M transistors that are used as a buffer stage. The 601 requires a large heatsink for its mosfet output, but here the four D882M transistors are mounted to the bottom of the board and don’t require the large heatsink used in the smaller sibling. Those interested in the D882M can find the datasheet here. Capacitors are either Elna Silmic or RubyCon branded throughout. The 602 also lists a built in mute circuit in the headphone output to prevent pops at power on. This either isnt present in the 601 or simply isn’t mentioned in the documentation. The 602 lists gain as +15dB so is slightly lower than the 601 in that measurement, but output power is much larger at 1300 mW into a 32Ω load compared to the 200mW of the 601. SNR is improved as well at 115dB compared to 100dB (601) while THD+N is not quite as good at <.1 at 1kHz with a 32Ω load. The 602 lists as suitable for use with headphones between 16 and 600Ω impedance and indeed was capable of powering just about anything thrown at it. The 6AK5 (6J1 Chinese designation or EF95 Euro designation) gives the user plenty of options to roll tubes in the 602 (an exercise I intend to do a bit later), as the 6AK5 has been in nearly constant production since the 1940s when it was introduced by Bell Labs and Western electric and used in early radar systems in fairly large numbers. It is not uncommon to find western electric examples with USN and an anchor on the packing designating those tubes accepted for military use during the war.






Sound:

Normally the goal of an amp is to be gain on the wire and nothing else, but when we introduce a tube pre, it almost always has an impact on the signal in an audible way. So here we can talk about coloration as not only expected but welcomed. Those who want to avoid such coloration of the sound will likely opt for one of the many solid state amps that are available instead anyway. The MT-602 utilizes the 6AK5 tube family. This family also includes tubes labeled 5654, 6J1 (Chinese and Russian designation), CV4010 (British), EF95 (Euro), 403a/b (Western Electric) as well as 6AK5W and 5654W designations. The tube was originally used in radar sets and was used in a ton of military equipment over the years so they are commonly found as new old stock in military stockpiles. With nearly constant production from the early 1940s through today there are too many options to possibly account for all of them but they are somewhat less common on the market than 12au7 or 6DJ8 pre-amp tubes that are commonly used in this type device and may require a bit more digging to surface satisfactory pairs for use in the MT-602. I am working on a tube rolling article and will add the link here when completed but will suggest the early Sylvania JHS 6AK5 as a good all-around tube with better stage size and tonality than the stock offering. When used a pre-amp, I also found the Western 403b to be a good option as it complemented the Klipsch R-R1PM and Kanto TUK powered monitors I had available well.


Thoughts / Conclusion:

I had mixed emotions about the little brother in this series as I think it was of somewhat limited utility and should be thought of more as a pre-amp with a earphone output than a bonafide headphone amp. I have no such reservations here. The MT-602 offers good power and was able to handle all but the most demanding headphones without any issues. The pre-amp function worked very well using both powered monitors and in place of my standard pre-amp in my home system (which is asking a lot). If there is a drawback it is that as a pre-amp you only have a single RCA input on the rear and 3.5mm jack on front and no switching to handle which input is in use. This limits the 602 to being a single source pre-amp. Thankfully for most this will be part of a desktop stack and will probably be asked to handle output from a DAC or perhaps directly from a PC sound card. I think this is the role Xduoo envisioned the MT-602 being used in and it performs quite respectably when used as such. The 5654W miniature tube has a lot of options to tune the sound to the end-users liking although it does puzzle me that the 601 went with the more expensive and more commonly available 6DJ8 while the bigger brother went the minature route. I suspect this was in order to keep the cases on the two models the same size and dual 6DJ8s simply could not be fit in the same space. I’m not sure I would have chosen the case size as my over-riding variable here as going with a more common tube would open up even more options for buyers to tune and tweak the device.

For those interested, I have a tube rolling the MT-602 article posted to my blog. Rules here prevent posting a link so google MT-602 Tube Rolling.