🔷 xDuoo MT-604

This is the official thread for the Xduoo MT-604

This thread is for discussion and reviews.

  • Balanced ONLY
  • Hybrid Design
  • Independent Volume Controls

:red_circle: Hifiguides Amazon Link


Z Reviews


Ordered mine yesterday.

I have the MT-602, based on the previous review. I bought GE Tubes and now I think it sounds awesome. Standard tubes didn’t push bass enough.

He is right about the volute however, it is insanely loud. INSANE.

I can run my 6xx’s on it and they sound just as good.


I’ve had my M604 for a while now. I am still stunned every time I listen to it.

I run 24bit/96k or 192k Flac files via Onkyo C-N7050S CD/Streamer, through Music Hall 2.0 pre-amp (variable output), connected via RCA to XLR cables. The M604 is maxed out and I control volume via the pre-amp. Obviously, I can also listen to CDs and vinyl (which sounds amazing) on the same set-up.

I can attach my FiiO M9 DAP via a 2.5mm to 4.4mm converter cable. Once again, a sweet sound.

I use a 4.4mm to 3.5mm converter to listen to single-ended headphones, which also sound fantastic.

All-in-all, for £120, this is a no-brainer, if you like a tube sound and expansive soundstage.

Now to start tube rolling!!

Here’s another review.

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Can you share a link to the 4.4 to 3.5 converter you use for single ended headphones? Thanks

This works fine with my HD58Xs, Momentums, and AKGs

There is also a 2.5mm version.

Hope this helps.

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I guess I have to say this about balanced to unbalanced conversion.

To start, a single ended connection usually uses 3 connection, a right channel, left channel and a shared ground connection, while a balanced connection uses four different connection (rarely five for a ground), a positive and negative for the left and right channels . So what happens if we want to convert a balanced headphone to a single ended source? We can simply combine the negative left right connection as a shared ground and keep the positive right left connection as separate. But what if I want to convert a single ended headphone to a balanced source? First of all, the available connection that’s on the headphone is only 3 connection. So if you are going to convert it, you have to combine the negative left right of the source into a shared ground. This is quite dangerous because you run the risk of short circuiting your source. But my amp still works just fine !!!11!one!! Well, every amps are made differently. There are only two cases that can happen, that is either you short circuit the source or you fatigue the source with unnecessary load that it isn’t designed for. Fatiguing the source may also shorten the life of the source. So to easily remember this, balanced source must always be paired with balanced headphone, while balanced headphone can be paired with single ended or balanced source.

But, if what you care is for your single ended headphone to make sound out of your balanced source, then do whatever you want. I just want everyone to know the risk of converting single ended headphone to a balanced source.

My recommendation

Personally, I would recommend to have all of your headgears cabled in a balanced termination. This can be done by buying a balanced cable out of the store, or doing a DIY to recable the headphone. The benefit of having all of your headgears in balanced termination is that you can plug it to anything as long as you have the correct adapter. You can have a cable system like the one from HAC that uses a mini 4 pin XLR or you can have all of it terminated in 4.4mm and buy all sorts of adapters like what I do.


I’m honestly surprised that you were able to convert down to se. Many amps will trigger overcurrent protection if you try that. Now I’m wondering if it’s designed fully balanced. Can you do a continuity check on the two grounds?

Thoughts on this coupled with my IOTAVX SA3?

Been hunting for a headphone amp for a while.

Did I just figure out what’s getting connected to the balanced output of my ZEN DAC?


As others have mentioned here, be careful converting balanced out from an amp to single ended cables for headphones. That adapter is to go from 4.4 balanced to 3.5 balanced, which is 4 pole, not 3.5 single ended, which is 3 pole. Depending on the amp and how the adapter is wired, it is technically possible to convert from 4.4 balance to single ended since the 4.4 is 5 pole and can include ground. By dropping the negative signal from each channel, it becomes a standard single ended with common ground. If that’s not how the adapter is wired, or if the ground is not passed to the output, it could end up not working at best, or damaging gear at worst.

Don’t know what a continuity check is. However, I’ve used the same jack on Loxjie P20 and IFI HIP DAC and both play my HD58Xs and other 3.5mm headphones without any issues.

The P20 has a 4.4mm output jack now? Regardless, based on the description, it does look like they designed that adapter specifically to be compatible with the wiring of specific devices, such as the Cayin N6ii where the negative signal from each channel is dropped to convert to single ended. This would be similar to the ddHiFi DJ30A. I’m not sure how they’d accomplish making it both balanced and single ended 3.5mm compatible, though.

I have no idea how it works, but results-wise it’s a winner.
I’ve never tried it with a 3.5mm balanced.
It may be that the product description is incorrect and only works SE. I don’t have a balanced 3.3mm cable to test it.

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Short initial impressions: I am having a lot of fun listening to this amp. While owning a Darkvoice 336 prior to this, I wasnt as much a fan of the stock tubes. Unfortunately I cant compare the two because the Darkvoice had to go back to DROP after a tube failed. From my memory though the effect of tubes is certainly there with this amp. For the $150 I paid for the MT-604 I am extremely pleased with the sound. Also using my SU-9 as a volume control is a god send.

Current Equipment chain:
PC>>USB>>SMSL SU-9>>Xduoo MT- 604>>Hifiman Ananda

How does it compare to the solid state amps you’ve heard?

I have a thx 789 currently. My current setup is PC>>USB>>SU-9>>> XLR switch box>>> (THX789)X(MT-604)>> headphones. I maxed out both amps on volume and use the SU-9 to control volume. I can do a sit down A-B comparison tonight. From my first observations. I feel the MT-604 had more body than the THX. The MT-604 has that smoothing effect of softening the top end like trumpets or flutes that tubes seem to provide. I’ll make sure to match dB and do a better analysis tonight when I get home. Last night was like 40 C and I was more concerned with my ear pads getting soaked in sweat haha.

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Ive spend a bit of time now comparing the two. One word kept coming up in my notes. Intimate. The MT-604 (when contrasted to the THX) has a more compact sound stage. I used the Ananda and HD6xx to test this. While I didnt really notice a huge difference with the Ananda, the 6xx for some reason made the “narrow effect” more pronounced. So I primarily used the 6xx for the comparison. The first song I noticed this on was Mighty Mighty by Earth Wind and Fire. There is a female vocalist to the left and when listening to the track through the THX, I described her as standing to my left with her speaker beside her. I would be at the front of the stage and shes standing just up and to the left. With the MT-604 its as though shes taken a knee and is singing to the side of my head. Like the speaker is behind her.

I would say the most noticeable thing between swapping would be the loss of space going from the THX to the MT-604. I dont mind it for the most part but it can make certain songs a bit overwhelming. Not to the point of being unbearable, but certainly more compacted and close. An example would be Chicken Dog by Jon Spencer Blues Explosion. With the THX its comparable to standing in a room with the speaker for the guitar about an arms length away. The MT-604 takes your face and pushes it into the tweed and tolex of the amp. Its almost too much.

Donald Fagen and I.G.Y sounds great through the MT-604. Not much to say other than its intimate but in a good way because i suspect the man spent months mixing it just right haha.

Final Fantasy Distant Worlds and a New World Collections - Track: Liberi Fatali
MT-604: Sitting in a small theater with a more compact band pit.
THX: Sitting in a larger theater and having a bit more elbow room.
Like its not bad either way. The THX was a better choice for this track due to its ability to create a nice sound picture. The MT-604 just seems to reduce the instruments into sections rather than individual parts. I think its the intensity that does the 604 in here.

Where the 604 did a great job was on the track Balamb Garden. The slower pace and more even tempo gave me the effect of a relaxing evening listening to the symphony at home. The THX had a more in person feeling.

Life’s Greatest fool by Gene Clark. MT 604 was the winner here. It brings the piano in and makes things seem more together than the THX.

I have a few more songs that I listened to. My main take aways were that the MT-604 is a good amp. It does things that my THX cant; mainly making things more intimate. I cant say its as tubey as a Darkvoice or full tube amp. The 604 makes things less fatiguing if the song is slower paced. As soon as the pace picks up in something like a jazz song, Instruments begin to walk on one another. Would I reccomend this amp? Yes!. Would I say this is tubey enough to satisfy those looking for the goo? Hard to say. The stock tubes are okay but not as goo inducing as I was imagining. Tube rolling is certainly a possible fix though. Am I happy with my purchase? Yeah! There are some intageable’s here and some things that are possibly subconscious. I find there to be less of a pressure on my ears when I listen to the MT 604. I cant put a finger on it.

Hopefully this was helpful? Im not too great at describing these things.


I’m surprised to hear you found the sound stage to be noticably more narrow than when on solid state. You may want to try some other tubes.
How was the 604’s low end control? Any better or worse? Since you said instrument separation was worse, I’m guessing detail wasn’t as good either?

I’m not sure if sound stage is the right word, but the instruments seem closer together in my head. Certainly closer to my head when compared to the THX. I made sure to Db match so its not a volume issue. I can only assume its an imaging or sound stage attribute. The nice thing is the tubes are pretty common 6J1 tube, so trying new ones shouldn’t break the bank.

I’m not familiar with low end control. Im assuming it refers to the amps ability to produce a lower tone accurately. From what I can tell the base is a bit more pronounced but a bit muddy. Not a real clean bass. The THX seems to represent the bass notes better with more detail while the 604 seems to be more distortion than an accurate reproduction. As for detail retrieval the THX does that better. An example of the type of sound difference is in the song Liberi Fatali by Nobuo Uematsu. At the 1:17 mark there is a tapping like the conductor hitting his baton on the edge of a steel note stand. With the THX there is a sort of metallic tone to the hits. The 604 sounds like he is hitting wood. I want to say the Attack is more pronounced on the THX. That initial ping smack of the second it hits is more present. Its still a background detail though, not really night and day.

Out of curiosity I am wondering how the ideal tubey sound can best be described? I have always considered it to be akin to something like sanding a log. The sense of running your finger across a rough surface would be close in sensation to listening to the THX, and running your fingers over the same log but after it has been smoothed out a bit with sandpaper would be the 604. The effect is to give a more enjoyable sensory experience because sometimes you don’t want to hear every finger rub and accidental rimshot. Considering this explaination. I would say this amp (or at least stock tubes) is less tubey.

I listen to a lot of jazz. On the 604 songs like Pigalle by Kamaal Williams for example still have that dust crackle, but will still push the instruments close together ultimately making it hard to place the instruments in the head stage. Mind you later in the song there is a pretty enthusiastic trumpet that is pretty obnoxious. On both amps its just as obnoxious, but the 604 seems to take a bit of the edge off. I’d love to get some new tubey tubes to try and max out the goo factor.