1ET400A – Data Sheet

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Document includes the full specifications for 1ET400A

  • Single-channel, analog-input
    Class D amplifier module
  • Negligible THD and IMD
  • Extraordinary low noise
  • Load-invariant response
  • Exceptionally clean clipping
  • Low losses & high efficiency
  • Easy to integrate
  • Designed in Denmark


Output Power 425W @ 1% THD, 4Ω
Output Current ~25A
THD+N <0.00017% (~116dB) @ 100W, 4Ω, 20-20kHz
Dynamic Range ~131dB(A)
Output Noise 11.5μV(A)
Gain 12.8dB
Output Impedance <65μΩ @ 1kHz
Efficiency >94%
Idle losses ~1.7W (output stage)
Supply ±25V to ±65V DC
Size 82x63x35mm

1ET400A is a single-channel, ultra-high performance, analog-input Class D amplifier module capable of over 400W of power and provides an audio quality level that sets the standard for power amplifiers of any operating class. Its compact size and high reliability makes it fit a broad range of applications, while its audio quality makes it the undisputable choice even in applications where all the premium is on sound quality.

PURIFI’s continuing research into nonlinear control theory has produced the first mathematically exact largesignal model of self-oscillating amplifier controllers. This breakthrough allows complete optimization of the feedback circuit and improves performance by at least an order of magnitude over existing implementations. The amplifier module further incorporates a comprehensive protection system that makes it tremendously robust and easy to integrate.

These circuits and methods provide many practical and audible benefits:

  • High loop gain (>75dB) in the entire audio band
    • This figure corresponds to an unprecedented 110MHz Gain-Bandwidth Product and produces consistent ultra-high performance across the audio spectrum unmatched by audio amplifiers of any technology or operating class.
  • Negligible Intermodulation Distortion (IMD)
    • A very good measure for how well an amplifier handles complex signals. Sonically low IMD means a highly resolved and stable stereo image across the whole spectrum, even during very complex and busy passages.
  • THD remains extremely low at any frequency and any power level right until clipping
    • Translates into a total lack of sonic signature, and an ability to reproduce any type of music without preference for genres or production style.
  • Negligible output noise
    • No audible noise. Deep black silences and a generous and detailed sound even at very low playback volumes.
  • High power supply rejection ratio (PSRR)
    • The module places no particular demands on the power supply quality. A simple off-the-shelf unregulated SMPS will not degrade audio performance.
  • Load-invariant frequency response and negligible output impedance
    • The amplifier handles difficult loudspeakers with ease, including those that challenge most other amplifiers.
  • Controlled, second-order low-pass response
    • Very flat audio-band response with a sensible, 60kHz bandwidth.
    • Reduced sensitivity to out-of-band noise from DACs, reducing the requirements on the DAC reconstruction filter. This leaves a shorter signal path between DAC and loudspeaker.
    • Problem-free operation with outboard DACs over which you may have no control.
  • Very low idle losses and reduced electromagnetic interference (EMI)
    • The enormous loop gain allows relaxed timing of the power MOSFETs without degrading audio performance.
    • Idle losses are minimized.
    • Very little to no effort needed to pass regulatory tests.
  • Exceptionally clean clipping and clipping-recovery in both voltage and current domains
    • Clips cleanly and recovers immediately without “overhang”. Current limiting is equally instantaneous and glitch free. This guarantees the smallest amount of audible artefacts when pushed into clipping or overload protection.
  • Overall implementation/integration ease saves save time and cost for the system integrator
    • Architecture completely eliminates heterodyning in multichannel applications.