AUDIOPHONICS HPA-S400ET Power Amplifier Class D Stereo Purifi 1ET400A 2x400W 4 Ohm

Audiophonics HPA-S400ET Amplifier Class D Stereo Purifi 2x400W 4 Ohm
Class D stereo power amplifier based on two PURIFI 1ET400A modules and a HYPEX SMPS1200A400 power supply.

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Shipping date: 03-10-2023.

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Power Amplifier PURIFI 1ET400A 2x400W 4 Ohm

We are proud to present AUDIOPHONICS HPA-S400ET, a class D stereo power amplifier based on two PURIFI 1ET400A modules. This ready-to-use version is designed for audiophiles needing a foolproof amplification solution, with a considerable power reserve as well as impeccable linearity. The PURIFI modules are indeed among the most rigorous Class D amplification solutions on the market, with simply exceptional measured performance.

This device offers high level sound reproduction which will be suitable to drive demanding speakers, to sonorize large listening rooms or for studio applications requiring a considerable headroom without compromising on the precision and richness of the audio message.

All of the components are integrated in a sober and robust 100% Aluminum housing with openings and heatsinks to help heat dissipation. Its design also allows it to block signal interference.

Dual PURIFI 1ET400A module

  • Both channel of the amplification circuit uses its own PURIFI 1ET400A module. These high performance Class D amplifier circuits each offer a very comfortable power of 200W (@ 8Ω) while making the most of Class D amplifiers high efficiency rating.
  • The 1ET400A modules has a >75dB high gain loop over the entire frequency band, providing high performance across the whole spectrum and surpassing any amplifier regardless of its class.
  • Thanks to hyper-low intermodulation distorsion (IMD) the HPA-S400ET achieves incredible precision on its stereophonic image over the whole spectrum, unmatched by audio amplifiers of any technology or operating class.
  • THD remains extremely low at any frequency and any power level right until clipping. This translates into a total lack of sonic signature, and an ability to reproduce any type of music without preference for genre or production style.
  • The output noise is negligible, which allows deep silences and prevents losing details when listening at low volume.
  • The circuit benefits from a high level of rejection (PSRR) which minimizes the impact of power supply on audio performance.
  • Load-invariant frequency response and negligible output impedance enables the HPA-S400ET to drive the most demanding speakers with ease.
  • Very low idle losses and reduced electromagnetic interference (EMI). The High loop gain allows relaxed timing of the power MOSFETs without degrading audio performance.
  • The HPA-S400ET uses these amplifier modules with an interface card specially developed for optimal integration.

Power Module Hypex SMPS1200A400

The SMPS1200 switching power supply is a model with very high maximum output power of 1200 Watts. It has been specifically designed and developed by Hypex to provide 2 x 64V voltage required for operation of the most demanding amplifier modules.

This low noise high quality Power supply, meets every energy needs of the amplification modules.

Audiophonics Interface Card

Both modules are driven in opposite phase, to cancel out the «Power-Supply Pumping» effect. This allows greater stability in the power supply by alternately distributing current draws on each rail, thus increasing its overall capacities.

We opted for a two stage voltage regulation in order to optimize the power supply to the OPAs and the auxiliary voltage supplied to the modules. 

A Texas Instrument LM4562 OPA per channel is used, these are very low distortion AOPs offering the greatest transparency with a very low THD. They are mounted on socket allowing their replacement if necessary

To suit all uses we opted for 3 gain settings, adjustable by jumper on the interface board.


Designed for easy integration, the HPA-S400ET has a balanced stereo (XLR) and unbalanced (RCA) input. Bipolar selectors make it easy to change the input source and even allow independent channel control.

On output side, BP-207 Carbon / Gold 24K Ø5.5mm speaker terminals ensure excellent connection with the speakers.

A trigger module allows the amplifier to be switched on automatically from a distance. This is compatible with voltages from 5 to 12V.


Frequency response

THD vs Freq

Test du Audiophonics HPA-S400ET par Audio Science Review (Amir)

The Audiophonics HPA-S400ET comes in a beautiful package with super performance to match its good looks. Yes, it builds on Purifi's excellent platform but they managed to add value without messing with its performance. The gain settings are well thought through. The whole thing is so well executed and must be a delight to our European members who can buy it locally. Having been built in France, it is also a feather in the cap of our French members. I am happy to give my strongest recommendation to Audiophonics HPA-S400ET. You have a lot of power with superb fidelity and transparency. "
Test du Audiophonics HPA-S400ET par Audio Science Review (Amir)
TypePower Amplifier
Output power (max)8Ω @1%THD : 227W
4Ω @1%THD : 425W
2Ω @1%THD : 450W
THD+NPO=1W, f=1kHz 0.0007 %
PO=10W, f=1kHz 0.00026 %
PO=100W, f=1kHz 0.00015 %
PO=1W, f=20-20kHz 0.0007 %
PO=10W, f=20-20kHz 0.00029 %
PO=100W, f=20-20kHz 0.00017 %
IMD (CCIF)PO=1W, f=18kHz+19kHz 0.00025 %
PO=10W, f=18kHz+19kHz 0.00022 %
PO=100W, f=18kHz+19kHz 0.00027 %
IMD (DIM)PO=1W, DIM30 0.002 %
PO=10W, DIM30 0.002 %
PO=100W, DIM30 0.002 %
Idle noiseA-weighted 11.5 µV
Dynamic rangeA-weighted 4Ω 131 dB
SNRA-weighted 4Ω 131 dB
Frequency responseRL= 8Ω, f= 20-20kHz ±0.01 dB
RL= 4Ω, f= 20-20kHz ±0.01 dB
RL= 2Ω, f= 20-20kHz ±0.01 dB
Output impedance1kHz, Iout=1A 0.07 mΩ
20-20kHz, Iout=1A <0.65 mΩ
Input impedanceRCA: 47kΩ / XLR: 94kΩ
Bypass: 2.2 / 4.4 
Power supply230V (110V on request)
Dimensions413 x 322 x 60mm
Weight5.63 kg
Power cableIncluded
Data sheet
OutputSpeaker terminal
ChannelDual Mono
ClassClass D / T
Amplifier chipPurifi 1ET400A
Power (W)400.0
Remote ControlNo

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Average votes
4.7 / 5
23 reviews
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Very good choise
I didn't expect such good sound quality in all aspects for this price. Audiophonics service and delivery are, as always, at the highest level. I highly recommend.
This review has been posted for AUDIOPHONICS HPA-S400ET Power Amplifier Class D Stereo Purifi 1ET400A 2x400W 4 Ohm
Note :
Date :
Une révélation en matière de transparence, de fluidité et de détails
Je souhaitais avoir un amplificateur de puissance Hi-Fi qualitatif sur mon système multicanal (j’écoute pas mal de vidéos, plutôt musique classique) et les deux enceintes colonnes Triangle Signature Delta qui sont dynamiques et brillantes dans l’aigu souvent associées à des amplis à tubes et assez exigeantes au niveau de l’électronique associée, mon amplificateur intégré multicanal est le Denon 8500HA plutôt adapté à ce type d’enceintes et assez neutre.
Un modèle Purifi, système d’amplification réputé pour leur neutralité et leur transparence ainsi que leur finesse musicale, s’avérait être une bonne option, mais généralement prix élevé comme chez NAD. Ce HP-S400 ET a retenu mon attention, prix intéressant et performances sonores impressionnantes (mesures et qualités musicales), les avis sur ce site ont fini par me convaincre, ainsi qu’un échange avec le conseiller d’Audiophonics.
Depuis que je l’ai connecté à mon système, jusqu’ici j’avais un Nuprime MCX (classe D également) plus usage Home Cinéma et musique, là, avec l’HP-S400 ET, j’avais des détails beaucoup plus fins et retranscrits précisément et un équilibre très naturel, très bonne spatialité (largeur et profondeur). Très agréable à écouter, musical, neutre et fluide, je pense vendre le Nuprime, sur cette catégorie d’ampli de puissance à moins de 2000 euros, peu de propositions de la part des constructeurs.
Cet Audiophonics a une valeur exceptionnelle à mon avis, sa facilité à fonctionner avec beaucoup de configurations (préamplis et enceintes), je ne pense qu’il y a peu de concurrents à son niveau en classe D, très pratique lorsque l’on n’a pas l’espace suffisant pour des amplificateurs plus volumineux et lourds comme les classes AB ou A. De plus, pour ceux qui s’en servent sur une configuration Hi-Fi avec un meilleur préamplificateur, la qualité sonore doit être encore plus élevée.
This review has been posted for AUDIOPHONICS HPA-S400ET Power Amplifier Class D Stereo Purifi 1ET400A 2x400W 4 Ohm
Note :
Date :
A hell of an amplifier
This my first Class D amplifier, I enjoy it now for 15 months. And oh boy what a clean, powerfull and beautiful device it is! Well built, beautiful design. No remote contol but it has tirgger in/out so... no worries. Still one remark about the design related to ones health: Lifting it up be advised because the cooling fins are sharp, one could cut oneself.
Audiophonics did a great job building this amplifier and the very custom friendly approach is superb! Delevery was perfect as well.
This review has been posted for AUDIOPHONICS HPA-S400ET Power Amplifier Class D Stereo Purifi 1ET400A 2x400W 4 Ohm
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Date :
A long-time user of only class A and tube amplifiers, this is a new great experience. I couldn't believe my ears how deep, wide and clean it sounds full of the most subtle informations, uniform and connected from bottom to the top into one huge picture full of beautiful natural details. This amp sounds just like your source, cables and speakers do.No less, no more,but beautifully big...Outstanding !!!. Perfect match with Topping pre90
This review has been posted for AUDIOPHONICS HPA-S400ET Power Amplifier Class D Stereo Purifi 1ET400A 2x400W 4 Ohm
Note :
Date :
Audiophonics HPA-S400ET
I must say that Audiohonics did it right compared to similar Purifi based amplifiers. It was worth the wait and I bought 2 of these! 2 American companies also make these but Audiophonics clearly made a higher quality amplifier. And I checked inside of both and took lots of pix. These also run very, very cool. compared to my tube amps. I will not compare these to my NAD M23 at more than twice the price. The NAD is not a fair comparison, NAD makes their own modules, also. This Audiophonics amp is serious competition to any amplifier if you are wanting an extremely transparent, clean amplifier. Audio Science Review was extremely impressed. They are notoriously tough reviewers/testers. But let your eyes and ears be the judge of course. I have several preamps to pair with these for now. But I suspect a preamp with XLR connections like my ancient Mcintosh MX130 or better may be needed to get the best out of these great amplifiers. Way to go Audiophonics!! Made in France!!!!!!!
This review has been posted for AUDIOPHONICS HPA-S400ET Power Amplifier Class D Stereo Purifi 1ET400A 2x400W 4 Ohm
AUDIOPHONICS HPA-S400ET Power Amplifier Class D Stereo Purifi 1ET400A 2x400W 4 Ohm
Class D stereo power amplifier based on two PURIFI 1ET400A modules and a HYPEX SMPS1200A400 power supply.

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