xDuoo MT-604 Balanced Hybrid Amplifier Review






xDuoo MT-604 Balanced Hybrid Amplifier Review





xDuoo is a Chinese company located in ShenZhen, China and is specialized in production of Desktop & Portable Headphone Amplifiers, Hi-Fi DAC’s and Portable Audio Players (DAP’s).



The xDuoo MT-604 is a relative small Balanced Desktop type Class-A Hybrid Amplifier with Tube + Transistor Circuits. It is the flagship model of the MT-60X Series and comes with both XLR and 4.4mm Balanced In- and Outputs, while each channel (Left & Right) has its own/independent volume wheel. The MT-604 features 4x 6J1 tubes and is able to produce an output power of about 2000mW @ 32ohm that is quite impressive.




I would like to thank xDuoo for providing me the MT-604 as review sample. I am not affiliated with xDuoo beyond this review and these words reflect my true and unaltered, opinions about the product.





Price & Availability:

The actual price for the xDuoo MT-604 is about $169,00 USD. More information’s can be found under the link below;




Package and Accessories:

The device comes in a white box with a glossy surface that sports the some xDuoo brandings on its surface.


This box contains the following items;

  • 1 x xDuoo TA-604 Balanced Desktop Amplifier
  • 1 x Power Adaptor & Power Cable
  • 1 x Print Material (User Manual, Warranty card, etc.)





Design, Buttons and Build Quality:

The xDuoo MT-604 is a relative small and quite lightweight Class-A Balanced Hybrid Desktop Amplifier, which has dimensions of 17x10x6cm (17×7.8x4cm without Tubes) and a total weight of approx 550grams. The chassis of the amplifier is made of sand blasted aluminum alloy material with a bluish-grey fisnish, which looks pretty nice.

On the front of the device are the xDuoo brand logo and two volume wheels in a stylish red color, one for the left and one for the right cannel. My only complaint about the otherwise beautiful looking volume wheels is that the positions are not very easy to see. Here are also the 4.4mm Headphone Input and the XLR + 4.4mm Headphone Outputs with labels under each port.

On the top of the xDuoo MT-604 are 4 (four) x 6J1 tubes that are surrounded by a stylish perforated surface, which are part of the cooling system.

At the bottom of the device are fours stands made of transparent rubber material.

Both the left and the right side panels do have the same diameter perforated surface that looks nice and helps to cool down the amplifier circuits.

At the rear side of the MT-604 are 2 (two) XLR inputs one for the Left and one for the Right channel that are surrounded with have screws and labels.

Here are also the Power ON/Off Key, the 12V/2A DC Power Input Port and some other labels (Model, Origin, Industrial Certificates, etc.) along with for additional fixing screws.

The build quality of the device is pretty good and fulfills the expectations from a product at this price level.





Technical Specifications:

  • Model                          : MT-604
  • Amplifier Type            : Class-A Balanced Hybrid Amplifier
  • Tube Model                : 6J1
  • THD+N                       : ≤0.01% (1kHz, 32Ω Load)
  • SNR                            : 115dB
  • Frequency Response : 10 Hz – 60 kHz (±0.5dB)
  • Dynamic Range          : 85dBA @ 32 Ω
  • Output Power             : 2000mW @ 32Ω, 1 kHz
  • Gain                            : +15dB
  • Impedance                  : 16-600Ω Recommended
  • Gain                            : +18dB
  • Inputs                          : 4.4mm Balanced + XLR (Left + Right Channel)
  • Outputs                       : 4.4mm Balanced + XLR
  • Size                            : about 17x10x6cm (17×7.8x4cm without Tubes)
  • Weight                        : 550g






Some Remarkable Hardware Features:

xDuoo MT-604 is a hybrid amplifier, which 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 warm presentation of tubes, but without losing the power and control of a solid-state solution. The MT-604 is adopting transistors for Class-A buffer, with output power up to 2000mW @ 32 ohm, which makes it suitable for different type of Headphones, Earphones or In-Ear Monitors ranging from 16 ohms up to 600 Ohms.


A. Tube + Transistor Hybrid Amplifier Circuit:

MT-604 adopts four 6J1 tubes for pre-amp and transistors for Class-A buffer. The front tube amplifier and rear transistor combine the advantages of two amplifier circuits.


B. Balanced Design:

MT604 is also a balanced tube headphone amplifier, you could find a pair of XLR balance input from the back panel. The front panel hosts a 4.4mm balanced input, 4-pin XLR and 4.4mm Balanced outputs. At the same time, this unit is designed to adjust the volume of the left and right channels separately to reject the sound bias problem.

I would wish that xDuoo have had add also an RCA input option beside the balanced inputs, which would make the MT-604 to a more versatile amplifier.


C. Additional Features:

The built-in relay inside the MT-604 mute’s the circuit when you turn on the amplifier, so that you can avoid any annoying POP noise. This makes sure that the tube could work at its best condition. For coupling capacitance, it uses Nichicon capacitance as the main filter capacitance and the special enthusiast Japanese Rubycon/Nichicon capacitance as the main filter capacitance.





Equipment’s used for this review:

Sources                       :  xDuoo MT-604, xDuoo XA-10, iBasso DX220 MAX, FiiO M11 Pro
Earphone/Headphone:  HiFiMAN Sundara, iBasso SR2, SIVGA P-II, Kinera Skuld, Moondrop Variations, iBasso IT01X






Albums & tracks used for this review:

  • Petra Magoni  – II Camello e il dromedario (Flac 24bit/48kHz)
  • Hayley Westenra – Odyssey Album (Dezzer HiFi)
  • Dionne Warwick – Walk On By (Flac 16bit/44.1kHz)
  • Sarah McLachlan – Angel (Flac 24bit/48kHz)
  • Sertap Erener – Aşk (Flac 16bit/44.1kHz)
  • Edith Piaf – Non Je Ne Regrette Rien (Flac 16bit/44.1kHz)
  • Diana Krall – So Wonderful (DSF)
  • Aretha Franklin – I Say A Little Payer (Flac 24bit/96kHz)
  • David Bowie – Heroes (Flac 24bit/192kHz)
  • Barry White – Just The Way You Are (Flac 24bit/48kHz)
  • Isaac Hayes – Walk On By (Flac 16bit/44.1kHz)
  • Sting – Englishman in New York – (Flac 24bit/48kHz)
  • Eric Clapton – Wonderful Tonight (Flac 24bit/96kHz)
  • U2 – Sunday Bloody Sunday (Flac 16bit/44.1kHz)
  • Armin Van Buuren – Vini Vici (Flac 16bit/44.1kHz)
  • Massive Attack – Angel (Flac 24bit/192kHz)
  • Really Slow Motion – Deadwood (Deezer HiFi)
  • Jo Blankenburg – Meraki (Spotify)
  • Lorde – Royal (Flac 24bit/48kHz)
  • Toutant – Rebirth (Deezer HiFi)
  • Portishead – It Could Be Sweet (Spotify)
  • Charly Antolini – Duwadjuwandadu (Flac 24bit/192kHz)
  • Gogo Penguin – Raven (Flac 24bit/192kHz)
  • 2Cellos – Let There Be Cello Album (Deezer HiFi)
  • Chopin – Nocturn No. 20 In C-Sharp Minor (Flac 16bit/44.1kHz)
  • Fazıl Say – Nazım Oratoryosu (Live) (Flac 16bit/44.1kHz)
  • Vivaldi – Le QuarttroStagioni “The Four Season” (Deezer HiFi)
  • Otto Liebert& Luna Negra – The River (Flac 24bit/192kHz)
  • Lunatic Soul – The Passage (Flac 16bit/44.1kHz)
  • Deftones – My Own Summer (Shove it) (Flac 16bit/44.1kHz)
  • Metallica – Sad but True (Flac 24bit/96kHz)
  • Opeth – Windowpane (Flac 16bit/44.1kHz)
  • Megadeth – Sweating Bullets (Tidal Hi-Fi)
  • Rush’s – Leave That Thing Alone (Flac 16bit/44.1kHz)
  • Slayer – Angel of Death (Spotify)s
  • Liquid Tension Experiment 2 – Acid Rain (Spotify)
  • Yosi Horikawa – Bubbles (Spotify)





The Sound:

The xDuoo MT-604 is a Class-A Hybrid (Tube + Transistor) Balanced Amplifier that offers a nice synergy while combing the openness and warmth of the Tubes with the power, resolution and dynamism of the Transistors. The result is a balanced and lush, dynamic and clean overall sound presentation, which good sense of imaging and staging.

This review is written after a burn-in period of 60 Hours. I have paired the xDuoo MT-604 mainly with the xDuoo XA-10 DAC/AMP and iBasso DX220 MAX. Sound impressions are based on pairings with headphones like the HiFiMAN Sundara, SIVGA P-II & iBasso SR2 and with earphones/IEM’s like the Moondrop Variations and Kinera Skuld.



Bass / Midrange / Treble / Soundstage:

The xDuoo MT-604 offers a decent sound performance for such an inexpensive, small and stylish looking Balanced Hybrid Amplifier. The lower register sounds pretty organic and is able to produce a nice sense of warmth that is never overdone.

The xDuoo MT-604 adds the subbass region of the HiFiMAN Sundara, Moondrop Variations and Kinera Skuld an additional amount of depth and intensity. The midrange region sounds gains slightly more body and impact without do shows any negative effects like muddiness. The resolution, extension and authority are quite decent for an Amplifier at this price range.

String instrument like cellos or violas are shown with a nice sense of depth and body, while percussion instruments like drums do sound impactful and controlled when I do listen to the xDuoo MT-604 with the Moondrop Variations and SIVGA P-II.


The midrange of the xDuoo MT-604 shows an additional breeze of warmth compared to sources like the iBasso DX220MAX or FiiO M11 Pro, while it still retrains a good level of transparency/clarity and airiness with all headphones and IEM’s I have listen to it.

The upper midrange is fairly energetic, detailed and fatigue-free with all IEM’s and Headphones I have tested with it, only the HiFiMAN Sundara did show an audible sharpness in higher volume level Petra Magoni in the song “II Camello e il dromedary”. The transitions in moments when electro guitars do sound with high distortion are in general quite controlled and smooth.

The treble range of the xDuoo MT-604 shows in general a good level of brightness and extension that was especially audible with the HiFiMAN Sundara and SIVGA P-II planar headphones. MT-604 is able to produce a good level of airiness and sparkle with all earphones and headphones I have paired with it. The lower treble range shows an efficient level of clarity and definition while the upper treble extension and sparkle is pretty sufficient for such a small hybrid amplifier at this price range.

The xDuoo MT-604 offers a decent performance when it comes to soundstage and imaging. The tube circuit plays a huge roll when it comes to the expansion and the space of the stage that shows an above average depth and wideness. The placement of instruments and vocals is fairly good especially when I do use the MT-604 with headphones like the HiFiMAN Sundara and iBasso SR2.





The xDuoo MT-604 is an excellent desktop type of Balanced Hybrid Amplifier for its price, which offers a pretty stylish look and a decent sound performance thanks to the use of Tube and Transitions circuits that does help to combine the best of both worlds.




Pros and Cons:

  • + Decent Sound Combination and Balance of Tube and Transistor type of Amplification.
  • + Lush & Organic Timbre
  • + Overall Balance from the Lows up to the Highs
  • + Pretty Good Level of Resolution with Respect of its Price
  • + Soundstage & Imaging
  • + Fully Balanced Circuit


  • – No RCA Input
  • – No XLR or Balanced Cables included to the Package
  • – Slightly amount of background noise when paired with sensitive IEM’s


Thank you for the Read!








You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *