SMSL H400MK2 – Fully-Balanced Desktop GaN Headphone Amp with 14× OPA1612A Op-Amps

[Kitty (S.M.S.L Marketing)]

Hello ASR members,

We're excited to officially introduce the H400 MK2, our new fully-balanced desktop headphone amplifier designed to redefine precision and performance for headphone enthusiasts and desktop audio users alike.

Every element of the H400 MK2 has been carefully considered: a high-power custom low-noise GaN power supply for clean, stable, and efficient power delivery; a fully balanced discrete component architecture that eliminates common-mode interference and preserves every sonic detail; and a premium op-amp configuration featuring 14 OPA1612A units working in parallel to further reduce noise and enhance dynamic performance. The result is an amplifier that delivers powerful, transparent, and exceptionally precise sound – letting you experience your music exactly as it was meant to be heard.

Built-in Custom Low-Noise Gallium Nitride (GaN) Power Supply​

The H400 MK2 features a specially customized low-noise gallium nitride (GaN) power supply. Compared with traditional linear power supplies, the GaN design delivers higher conversion efficiency and lower switching noise, providing the amplification circuitry with clean, ample, and highly stable power.

Key Advantages:​

• Low THD: The distortion (THD+N) is as low as 0.00006%, and the SNR is as high as 132dB!
• High Efficiency: Fully balanced discrete component design with massive output power.
• High output power:18W at 16Ω and 9W at 32Ω.

---

Fully Balanced Discrete Component Architecture​

The H400 MK2 adopts a fully balanced discrete component design. Every component is carefully selected and independently optimized, while each signal path is fully symmetrical to minimize interference from the source.

Whether it’s the subtle details of music or powerful dynamic peaks, the H400 MK2 delivers every nuance to your ears with exceptional purity.

---

Fully-Balanced Architecture with 14× OPA1612A Op-Amps​

At the heart of the H400 MK2 lies a fully-balanced discrete component amplifier design, incorporating 14 high-end OPA1612A op-amps to form a robust output stage.

Amplifier Highlights:​

• Fully-Balanced Design: Ensures superior channel separation and noise rejection.
• 14× OPA1612A Op-Amps: Delivers exceptional linearity and low distortion.
• Three Gain Settings: Low / Medium / High for optimal matching with any headphone or IEM.

---

Ultra-Compact Chassis with Premium Build Quality​

The H400 MK2 features an ultra-compact chassis crafted from high-quality aluminum alloy, providing a sleek and modern design that enhances space efficiency.

Precision CNC-machined from a single piece of aluminum, the chassis not only delivers a refined metallic finish and premium tactile feel, but also provides exceptional structural rigidity and heat dissipation. The aerospace-grade aluminum alloy offers excellent electromagnetic shielding, effectively isolating external interference and creating a clean working environment for the precision internal circuitry. Every edge and corner is meticulously finished, creating a refined and premium visual aesthetic.

---

​

Comprehensive Protection Circuitry​

The H400 MK2 is equipped with a full range of protection mechanisms, including DC, over-voltage, and over-load protection. Whether facing unexpected signal surges or improper operation, the protection circuitry responds instantly to safeguard both your headphones and the unit itself. Enjoy your music with complete peace of mind.

---

Inputs and Outputs​

Front Panel:​

• 4.4mm Balanced Headphone Output
• 6.35mm Single-Ended Headphone Output
• Balanced Headphone Output

• XLR Input
• RCA Input
• XLR Pre-amp Output
• RCA Pre-amp Output
• AC Power Input

---

Performance Measurements​

Parameter	Measurement Result
THD+N	-123dB, 0.00006% (1kHz, 32 Ω)
Signal-to-Noise Ratio (SNR)	132dB
Balanced Output Power (16Ω)	18Wx2
Balanced Output Power (32Ω)	9Wx2
Balanced Output Power (300Ω)	1100mWx2
Balanced Output Power (600Ω)	550mWx2
Unbalanced Output Power (16Ω)	5Wx2
Unbalanced Output Power (32Ω)	2.5Wx2
Unbalanced Output Power (300Ω)	260mWx2
Unbalanced Output Power (600Ω)	130mWx2

---

Data Proves It – Listening Comforts It​

Solid engineering and outstanding measured specifications form the foundation of the H400 MK2. Its sonic signature can be described in three words: accurate, pristine, and effortless.

The exceptionally high SNR delivers a dead-quiet background, allowing vocals and instruments to emerge with crystal-clear contours and precise imaging. The immense power reserves provide authoritative control — bass is tight and punchy, while dynamic passages are handled with agility and composure.

The H400 MK2 is not a "colored" or euphonic-sounding amplifier — rather, it functions like a high-resolution window, faithfully reflecting the source and recording without adding its own character. This allows listeners to focus entirely on the artistic expression of the music itself.

33Ω Load – 6.35mm Interface

33Ω Load – Balanced Interface

DNR

SNR

Frequency Response​

---

Conclusion​

For audiophiles seeking a flagship desktop headphone amplifier that offers pure, uncolored sound, immense driving power, and the ability to serve as a long-term "endgame" solution, the SMSL H400 MK2 is undoubtedly a product worth serious consideration.

Colorl: Black,Sliver

For more details, please visit our official website.
https://www.smsl-audio.com/portal/product/detail/id/955.html

 

[Limopard]

There's no kill like overkill. This device should be able to turn every low impedance headphone into ashes (and to drive the Lily Audio Genesis One up to moderate levels).

Price of USD 539 seems fair, though.

 

[tavaz]

What leaves me perplexed is the use of a fully differential structure (if it is true that it is used in the output stage) for a headphone amplifier. The advantages are obvious in the case of differential drive (4-connector headphones). But I understand that most headphones have 3 connectors with one end of the transducer connected to ground. This would require a design with a differential output stage that has one output shorted to ground. Obviously, there are cross-coupled designs available, but thought only of low-level signals; here we are talking about power (even if low).

 

[jsheard]

SMSL really needs to start putting 12v trigger on their gear, especially at the higher end. They're making a lot of separates which are meant to be combined into a stack but none of them can talk to each other.

Likewise with the new speaker amp they just launched, that doesn't have trigger either.

 

[Steakhouse]

18W. Good lord. They are really taking it to the max.

 

[MAB]

What leaves me perplexed is the use of a fully differential structure (if it is true that it is used in the output stage) for a headphone amplifier. The advantages are obvious in the case of differential drive (4-connector headphones). But I understand that most headphones have 3 connectors with one end of the transducer connected to ground. This would require a design with a differential output stage that has one output shorted to ground. Obviously, there are cross-coupled designs available, but thought only of low-level signals; here we are talking about power (even if low).

It's that connector!

Not uncommon to have this now.
The amp might also be useful to power a compression driver. I wonder how it does driving slightly lower impedance than 16 Ohms...

 

[Ruediger]

"14 OPA1612A"

Not bad... should drive any speaker my head can somehow carry with a leather strip.

I second the trigger topic though!

 

[Hoods_]

Could you give a tour of the options menu? Can outputs be activated and deactivated individually? Or if it has volume memory per output? Or is it more minimalist and simple? (Personally, I would prefer it)

 

[Kitty (S.M.S.L Marketing)]

There's no kill like overkill. This device should be able to turn every low impedance headphone into ashes (and to drive the Lily Audio Genesis One up to moderate levels).

Price of USD 539 seems fair, though.

Thank you for your comment!
We designed the H400 MK2 with one goal in mind: delivering high-end performance at an accessible price. At $539, we believe it strikes a great balance between power, precision, and affordability.
Thanks again for your feedback!

 

[Kitty (S.M.S.L Marketing)]

SMSL really needs to start putting 12v trigger on their gear, especially at the higher end. They're making a lot of separates which are meant to be combined into a stack but none of them can talk to each other.

Likewise with the new speaker amp they just launched, that doesn't have trigger either.

Thanks for your feedback – we really appreciate it!
You make a valid point about the 12V trigger. We've actually passed this suggestion along to our design team and will continue to push for it in future products.
Thanks again for sharing your thoughts!

 

[Kitty (S.M.S.L Marketing)]

Could you give a tour of the options menu? Can outputs be activated and deactivated individually? Or if it has volume memory per output? Or is it more minimalist and simple? (Personally, I would prefer it)

Thanks for your question! Here's a quick tour of the H400 MK2's menu options:
Menu Overview:

• Input Selection – XLR / RCA
• Output Selection – PRE OUT / HEADPHONE (switchable)
• VOL Mode – REAL TIME (instant) / SOFT (gradual, extends relay life)
• GAIN MODE – LOW / MID / HIGH
• DIMMER SETTING – Screen auto-off timer setting
• Brightness – Adjustable brightness level
• INFORMATION&RESET – Restore factory settings

To answer your specific questions:

• Can outputs be activated and deactivated individually?
  Yes – you can switch between PRE OUT and HEADPHONE in the Output Selection menu.
• Does it have volume memory per output?
  Yes! The H400 MK2 features independent volume memory for each output – so you can have different volume levels saved for PRE OUT and HEADPHONE, and the unit will remember them when you switch.
• Is it more minimalist and simple?
  Yes – the menu is clean, straightforward, and easy to navigate, focusing on essential functions without unnecessary complexity.

Hope this helps! Let us know if you have any other questions.

 

[Soundproof]

By the looks of it, it ticks off a lot of boxes. Might be that I'm outside the typical target/usage groups for audio gear, making my usage scenario irrelevant for sales volumes, but the showstopper tends to be the input array. To be useful to me, such device needs HDMI eArc, Optical (toslink), usb C preferably front and rear for my present and future sources. Not sure if the XLR and RCA outputs can be active simultaneously for a sub?

A bit pricier than my budget appreciate, but Luxin X9 seems to cover the spectrum I need apart from front USB C.

Otherwise attractive for my budget and level, typical SMSL source connectivity tend to be THE showstopper as far as I'm concered. Quite likely I'll get the AL400 as a placeholder to pass on 6 months later, but it kind of stops there for my scenarios. Can't remember to have seen a Dac/Pre/Headphone unit from SMSL for my needs. Hopefully that will change before I am done with my purchases, including a variant of the device in question.

On a sidenote:
Don't know if it is governmental regulations for use of VPN and so on causing this, but a few Chinese audio websites are inaccessible (to me) with "secure" DNS and VPN.

 

[Ruediger]

By the looks of it, it ticks off a lot of boxes. Might be that I'm outside the typical target/usage groups for audio gear, making my usage scenario irrelevant for sales volumes, but the showstopper tends to be the input array. To be useful to me, such device needs HDMI eArc, Optical (toslink), usb C preferably front and rear for my present and future sources.

I think you are looking at different devices. The AL400 is one that serves your need as a DAC with headphone amp.

This here is a headphone amp only, focused on max. performance in that area + the preamp function. To be fed by a DAC f.e.

Pretty high end combo with a DAC from the same design line.

Personally I am satisfied with the DO400, also for headphone.

 

[Soundproof]

My bad, braille next
For some reason incomprehensive to mankind, my mind was dealing with a dac combo.

 

[Hoods_]

Thanks for your question! Here's a quick tour of the H400 MK2's menu options:
Menu Overview:

• Input Selection – XLR / RCA
• Output Selection – PRE OUT / HEADPHONE (switchable)
• VOL Mode – REAL TIME (instant) / SOFT (gradual, extends relay life)
• GAIN MODE – LOW / MID / HIGH
• DIMMER SETTING – Screen auto-off timer setting
• Brightness – Adjustable brightness level
• INFORMATION&RESET – Restore factory settings

To answer your specific questions:

• Can outputs be activated and deactivated individually?
  Yes – you can switch between PRE OUT and HEADPHONE in the Output Selection menu.
• Does it have volume memory per output?
  Yes! The H400 MK2 features independent volume memory for each output – so you can have different volume levels saved for PRE OUT and HEADPHONE, and the unit will remember them when you switch.
• Is it more minimalist and simple?
  Yes – the menu is clean, straightforward, and easy to navigate, focusing on essential functions without unnecessary complexity.

Hope this helps! Let us know if you have any other questions.

Thank you very much for your reply. To be a little more precise, can I connect 3 headphones to the headphone output at the same time and choose which of the 3 outputs I'm going to use, or if I'm going to use all of them (like the Topping A70 Pro, sorry for the comparison, it's not really a suggestion)?

On the other hand, does the percentage volume have fixed steps? For example, does each percentage represent 1 dB or 0.5 dB? Thanks in advance

 

[Mnyb]

You can buy 4 pin headphone cables at Amazon to for example any Senheiser headphone, is it needed probably not

 

[tokyo_blues]

Hello ASR members,

We're excited to officially introduce the H400 MK2, our new fully-balanced desktop headphone amplifier designed to redefine precision and performance for headphone enthusiasts and desktop audio users alike.

Every element of the H400 MK2 has been carefully considered: a high-power custom low-noise GaN power supply for clean, stable, and efficient power delivery; a fully balanced discrete component architecture that eliminates common-mode interference and preserves every sonic detail; and a premium op-amp configuration featuring 14 OPA1612A units working in parallel to further reduce noise and enhance dynamic performance. The result is an amplifier that delivers powerful, transparent, and exceptionally precise sound – letting you experience your music exactly as it was meant to be heard.
View attachment 554621

Built-in Custom Low-Noise Gallium Nitride (GaN) Power Supply​

The H400 MK2 features a specially customized low-noise gallium nitride (GaN) power supply. Compared with traditional linear power supplies, the GaN design delivers higher conversion efficiency and lower switching noise, providing the amplification circuitry with clean, ample, and highly stable power.

Key Advantages:​

• Low THD: The distortion (THD+N) is as low as 0.00006%, and the SNR is as high as 132dB!
• High Efficiency: Fully balanced discrete component design with massive output power.
• High output power:18W at 16Ω and 9W at 32Ω.

---

Fully Balanced Discrete Component Architecture​

The H400 MK2 adopts a fully balanced discrete component design. Every component is carefully selected and independently optimized, while each signal path is fully symmetrical to minimize interference from the source.

Whether it’s the subtle details of music or powerful dynamic peaks, the H400 MK2 delivers every nuance to your ears with exceptional purity.

---

Fully-Balanced Architecture with 14× OPA1612A Op-Amps​

At the heart of the H400 MK2 lies a fully-balanced discrete component amplifier design, incorporating 14 high-end OPA1612A op-amps to form a robust output stage.

Amplifier Highlights:​

• Fully-Balanced Design: Ensures superior channel separation and noise rejection.
• 14× OPA1612A Op-Amps: Delivers exceptional linearity and low distortion.
• Three Gain Settings: Low / Medium / High for optimal matching with any headphone or IEM.

---

Ultra-Compact Chassis with Premium Build Quality​

The H400 MK2 features an ultra-compact chassis crafted from high-quality aluminum alloy, providing a sleek and modern design that enhances space efficiency.

Precision CNC-machined from a single piece of aluminum, the chassis not only delivers a refined metallic finish and premium tactile feel, but also provides exceptional structural rigidity and heat dissipation. The aerospace-grade aluminum alloy offers excellent electromagnetic shielding, effectively isolating external interference and creating a clean working environment for the precision internal circuitry. Every edge and corner is meticulously finished, creating a refined and premium visual aesthetic.

---

​

Comprehensive Protection Circuitry​

The H400 MK2 is equipped with a full range of protection mechanisms, including DC, over-voltage, and over-load protection. Whether facing unexpected signal surges or improper operation, the protection circuitry responds instantly to safeguard both your headphones and the unit itself. Enjoy your music with complete peace of mind.

---

Inputs and Outputs​

View attachment 554634

Front Panel:​

• 4.4mm Balanced Headphone Output
• 6.35mm Single-Ended Headphone Output
• Balanced Headphone Output
• XLR Input
• RCA Input
• XLR Pre-amp Output
• RCA Pre-amp Output
• AC Power Input

---

Performance Measurements​

Parameter	Measurement Result
THD+N	-123dB, 0.00006% (1kHz, 32 Ω)
Signal-to-Noise Ratio (SNR)	132dB
Balanced Output Power (16Ω)	18Wx2
Balanced Output Power (32Ω)	9Wx2
Balanced Output Power (300Ω)	1100mWx2
Balanced Output Power (600Ω)	550mWx2
Unbalanced Output Power (16Ω)	5Wx2
Unbalanced Output Power (32Ω)	2.5Wx2
Unbalanced Output Power (300Ω)	260mWx2
Unbalanced Output Power (600Ω)	130mWx2

---

Data Proves It – Listening Comforts It​

Solid engineering and outstanding measured specifications form the foundation of the H400 MK2. Its sonic signature can be described in three words: accurate, pristine, and effortless.

The exceptionally high SNR delivers a dead-quiet background, allowing vocals and instruments to emerge with crystal-clear contours and precise imaging. The immense power reserves provide authoritative control — bass is tight and punchy, while dynamic passages are handled with agility and composure.

The H400 MK2 is not a "colored" or euphonic-sounding amplifier — rather, it functions like a high-resolution window, faithfully reflecting the source and recording without adding its own character. This allows listeners to focus entirely on the artistic expression of the music itself.

View attachment 554635

33Ω Load – 6.35mm Interface
View attachment 554636
33Ω Load – Balanced Interface

View attachment 554637
DNR
View attachment 554638
SNR
View attachment 554639
Frequency Response​

---

Conclusion​

For audiophiles seeking a flagship desktop headphone amplifier that offers pure, uncolored sound, immense driving power, and the ability to serve as a long-term "endgame" solution, the SMSL H400 MK2 is undoubtedly a product worth serious consideration.

Colorl: Black,Sliver

For more details, please visit our official website.
https://www.smsl-audio.com/portal/product/detail/id/955.html

Hi Kitty can I quickly jump in with a semi random question.

First of all, I'm a user of your PL200 CD player. Love it.

Im looking to replace my Benchmark DAC I Pre. Do you have something equivalent in your lineup? DAC, and volume controlled preamp would be great. Optical or spdif digital inputs, USB and Analogue line in for a phono preamp. Headphone amp included would be a nice plus.

Thanks!

 

[MCH]

18W! Does it heat the pads too?

 

[Kitty (S.M.S.L Marketing)]

Thank you very much for your reply. To be a little more precise, can I connect 3 headphones to the headphone output at the same time and choose which of the 3 outputs I'm going to use, or if I'm going to use all of them (like the Topping A70 Pro, sorry for the comparison, it's not really a suggestion)?

On the other hand, does the percentage volume have fixed steps? For example, does each percentage represent 1 dB or 0.5 dB? Thanks in advance

To clarify: this unit only features a PRE OUTPUT and a Headphone Output. So, when you connect three pairs of headphones simultaneously, they all output audio at the same time.Regarding the volume control: yes, the volume adjusts in precise 0.5 dB increments.
Please let me know if you have any other questions!

 

[Kitty (S.M.S.L Marketing)]

Hi Kitty can I quickly jump in with a semi random question.

First of all, I'm a user of your PL200 CD player. Love it.

Im looking to replace my Benchmark DAC I Pre. Do you have something equivalent in your lineup? DAC, and volume controlled preamp would be great. Optical or spdif digital inputs, USB and Analogue line in for a phono preamp. Headphone amp included would be a nice plus.

Thanks!

Hi! Thanks for the kind words about the PL200, we're glad you love it!
To replace your Benchmark DAC1 Pre, I would recommend checking out either the SMSL DL400 or the SMSL D100. Both of these models are excellent all-in-one solutions that combine a high-performance DAC and a powerful headphone amplifier.