YDA138
●Pop Noise Reduction Function
The Pop Noise Reduction Function works in the following cases: Power-on, Power-off, Sleep ON/OFF, Mute ON/OFF, and
switching time between headphone amplifier and digital amplifier.
Pop noise at the Power-on, Power-off, and Sleep ON/OFF depends on the value of DC-cut capacitor for audio input signal.
The smaller the value, the greater the effect on the pop noise reduction; however, 1µF of capacitance is recommended in the
consideration of the low frequency cutoff.
●Correspond to Filter less
Normally, when LC filter is not used, carrier signal of 50% modulation comes into speaker even in MUTE state and causes
significant loss, and as the result the speaker is heated.
Generally, 10W speaker or so is considered to have inductance component of not less than 20µH.
In the modulation method of YDA138, duty ratio of the carrier signal is several % in the MUTE state, so the speaker
inductance component can sufficiently inhibit speaker loss without LC filter; therefore, the speaker is not heated.
●Speaker Inductance
When YDA138 is used without LC filter, speaker inductance component reduces speaker loss in the MUTE state; therefore,
use a speaker with inductance component of 20µH or more at the carrier clock frequency.
●LC Filter
When connecting LC filters to YDA138, make the following LC filter circuit. Use the following constant in accordance
with speaker impedance. By using the following constant, low-pass filter with cutoff frequency=50kHz or so, Q=0.7 or so is
configured.
LC Filter Constant
RL
4Ω
8Ω
16Ω
L1
C1
C2
10μH
22μH
47μH
0.47μF
0.22μF
0.11μF
0.01μF
0.01μF
0.01μF
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YAMAHA [ YAMAHA CORPORATION ]
