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 //
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
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) ...”
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