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Biipolar-input audio operational amplifier
  AS401/AS401A - Hi-end audio bipolar input amplifier

    AS401/AS401A , bipolar-input audio operational amplifier with class A output stage, achieves very low THD levels under high load (600 Ohm & 300pF) via wide frequency range (0,00036 % & 40 kHz) and Vout=7V rms. Amplifier benefits from big phase margin 125° & (+1, Rl=600 Ohm // Cl=100pF) and 60° & (+1, Rl=600 Ohm // Cl=330pF) .
    High slew rate 30 V/usec ( G=+1 & Rl = 600 Ohm Cl = 330 pF) , wide bandwith (> 35MHz), low offset voltage 250µV, makes AS401 perfect choice for Hi-End audio equipment.
   AS401A benefits from additional balance inputs (offset trimming) and additional pin for case shielding.


Customers reviews:

    At the moment, I have performed only a “physical” start and initial comparisons  with two monolithic op-amps with a bipolar input in the cascade of a differential signal subtractor of DAC AK4497.
    The first results are very positive with the direct replacement of LME49710HA with AS401.
    For the test 1 kHz signal, there is a decrease in the 2nd harmonic level by 1dB, the 3rd - by 2.5 dB, the 4th - without change, 5th - at 1.5 dB.
    For a test signal of 19 + 20 kHz with a peak sum level of 3 V, the 1 kHz difference tone decreased by 3.5dB - ( from -119 to -122.5dB). The total tone 39kHz decreased from -102 to -108.5dB.
    Comparison with LT1028 is even more in favor of AS401, especially in the total tone of the dual-frequency signal. OPA1611 is significantly worse in terms of high-order component distortion (8 ... 10 and higher) ...”

    I replaced the op-amp OPA1611 with a AS401 in the DAC with the AK4493. With AS401 I noted a more full-bodied, rich and more structured sound in the low frequency range of the audio range. Voices of artists acquired great plasticity and physicality. The sound in the high-frequency region has become less intense and more analog. ...”


  AS401-AS402 comparative review in Hi-End Audio-DAC application - by Dmitry Andronnikov

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