Audiophonics HPA-S400ET Amplifier Class D Stereo Purifi 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: 07-12-2022.

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This device is supplied as standard in 230V. If you need 110V input voltage, please specify it clearly in the comment field when ordering.


Power Amplifier PURIFI 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 card:

  • Gain of + 7.2dB, for a total of 20dB - Maximum power reached with a signal of ~ 4.2V RMS
  • Gain of + 12.5dB, for a total of 25.3dB  (default) - Maximum power reached with a signal of ~ 2.2V RMS
  • Bypass: in this case the signal passes directly from the inputs to the modules, allowing the lowest possible gain of 12.8dB. This mode can be interesting when using a powerful preamplifier, capable of driving a load of 2 to 4kOhm and reaching a voltage of ~ 10V RMS


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
Light symbolYes
ClassClass D / T
Fuse holderYes
Amplifier chipPurifi 1ET400A
Power (W)400.0

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Average votes
4.6 / 5
14 reviews
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Date :
This is the one.
Excellent build quality. Excellent sound. Simply no faults to be found. I'm not sure how one would find something better, except by trying many others with similar quality-characteristics and then preferring a greater coloration/distortion to the sound. Along those lines, I ordered the Sparkos op-amps as an extra purchase and installed them myself to test. Honestly, there is starkly little difference. However, I did very slightly prefer the Sparkos and left them installed. For the information of others who may research this choice, I'm 100% happy. The USD/Euro ratio is favorable right now if you're ordering from the US, and the shipping cost is not expensive at all (price it in your cart). My goal was to get streamed high-definition recordings to my ears with as little deviation from the source recording as possible. To that end, I run the streamed music through an RME-ADI 2, then (via XLR) to this amplifier, at the "low" jumper setting for the Audiophonics. Bi-wired handmade (but not expensive) cables run to the Eminent Technology LFT-8b speakers. The RME has plenty of output and can effectively serve as a preamp for digital sources. I listen to all kinds of music for pleasure, though I am a full-time professional orchestral/chamber/solo musician by trade. Thus, my preference for the straightest path to the musicians where possible. I happily acknowledge that there are likely systems of music reproduction that I would like better than what I have here now -perhaps more colored, perhaps somehow less. Having said that, I've never heard anything I've liked better. Buy this amplifier with complete confidence.
This review has been posted for Audiophonics HPA-S400ET Amplifier Class D Stereo Purifi 2x400W 4 Ohm
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Date :
Very very nice
It is an amp in class D that is worth all the money and some. The finish from audiophonics is very very nice. But is not going to work for me with the gain on in any position. With sparkon or not is not worth the money. When you desble the gain and put xlr with 4v to 10v output in class A si wonderful. On my opinion is better than jeff rolland. 10+++ for the build -1 for output integration
This review has been posted for Audiophonics HPA-S400ET Amplifier Class D Stereo Purifi 2x400W 4 Ohm
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Date :
M David B - Audiophile Scientifique
J'ai remplacé mon ampli ART SLA2 (en class AB) par HPA-S400ET pour alimenter mes enceintes Magnepan 3.7i.
L'échange avec le service technique très cordial, on sent clairement la maitrise technique et la très bonne connaissance du produit (c’est pas un service commercial délocalisé essayant de faire de la figuration).
Commande passée le vendredi 11 mars 2022 à 11h00, Livré le lundi 14 mars 2022.L'emballage - double semble être à toute épreuve !
La différence de qualité du rendu sonore est très nette. Les aigus sont bcp plus clair et les basses ne bavent pas ! La différence se perçoit même dans des pièces éloignées de la maison.
Les finitions de l'appareil sont impeccables et renforcent utilement l'aspect qualitatif !
Je tenterai sans doute plus tard de tester avec d'autres OP comme les OPA1612 pour voir…
This review has been posted for Audiophonics HPA-S400ET Amplifier Class D Stereo Purifi 2x400W 4 Ohm
Note :
Date :
My old amplifier was Tripath ta3020 based self-assembled power amplifier.

This purifi-based amplifier is really well assembled and looks better in real life than in pictures. I asked white led for the power button and this is what I got. The led is a little bit too bright thouhg. The speaker terminals are nice quality but the carbon fibre detailing is kind of silly.

Sound of the amplifier is powerful, really well detailed and neutral. Bass is really well controlled. Soundstage is wide, somewhat deep and airy. The performers are a little bit forward compared to my old amp. Sound of the vocalists is really lifelike. The noise from the amplifier is really minimal, I can hear some hiss when I put my ear next to the treble element, but this is not perceivable from 1m.
This review has been posted for Audiophonics HPA-S400ET Amplifier Class D Stereo Purifi 2x400W 4 Ohm
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Date :
Musical et polyvalent
Très bon rapport qualité prix;
Très silencieux même sur enceintes à haut rendement de 103db
La dynamique et la transparence sont encore meilleures en mode XLR
This review has been posted for Audiophonics HPA-S400ET Amplifier Class D Stereo Purifi 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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