IC 74HCT125 are transmitted to audio signal processing IC TAS5508 to be processed (specific IC
data please refer to Attachment), then 10 groups of PWM signals are output, six of which are
transmitted to power amplifying parts, two of which to headphone output and two of which to
auxiliary cha nnel output.
Six groups of signals transmitted to power amplifying IC are processed by surrounding and super
DBB sharing an N13 IC TAS5508, and by main sound channel and center sharing an N14 IC
TAS5508. Signals are amplified here, for they are digital high frequency signals, they have high
efficiency; meanwhile power IC has low colorific value. Amplified signals are still digital signals,
in order that they can be output through loudspeaker, amplified digital signals still have to be
processed before outputting.
For PWM signals containing audio signals, since high frequency signals have high frequency and
are beyond audibility range of human ears, we can ignore impacts of high frequency signals and
reduce low frequency audio signals only during processing.
TAS5508 is an 8-channel pulse width modulated high performance IC, and applicable in
processing most digital audio signals. Between 20Hz and 20KHz, it has excellent noise factor and
dynamic range. It has following features:
1
、
Automatically control clock speed and digital sampling speed;
2
、
8 groups of audio input channels;
3
、
8 groups of PWM output can be changed into 6-channel stereo line output or 8-channel
line output;
4
、
Line output is a different input open loop amplifier driven by a group of PWM signals.
IC TAS5112 is a high performance audio power amplifier. Bridging with 6O loading, each channel
can output 50W. It has 95DB dynamic range, low distortion degree and low rate of heat generation
with power efficiency up to 90%. It also has functions of low-voltage protection, high-temperature
protection, overflow protection, etc. At the same time, it has built- in driving power adjustment gate
circuit. It is applicable in family video, DVD receiver, mini music center, etc. Detailed IC
introduction see Attachment.
When in normal disc reading, digital signals and clock signals from 1389 are transmitted to pin 26
to pin 31 of IC TAS5508 through IC 74HCT125 gating. If no headphone is inserted, PH-SEL is of
high level, as well as when MUTE is normal. And pin 37 of TAS5508 is also of high level. All data
lines and clock lines can be detected by oscilloscope. One group of signals from 5508 is
transmitted to N8 and N9, then output through auxiliary channel. Another group is transmitted to
headphone; other PWM signals are transmitted to amplifying parts of amplifier.
When headphone is inserted, PH-SEL signal is forcibly shorted to earth, and turns to low level,
meanwhile amplifier is muted.
This amplifier has functions of radio reception, auxiliary channel output and karaoke. All external
inputs after N3 CD4052 gating and N7 CS5340 analog-to-digital conversion are transmitted to
MT1389. Rear processing and output is the same as the signal output flow in normal disc reading.
When in disc reading, system defaults to gate karaoke input, therefore you can open karaoke when
playing disc. This amplifier also has automatic accompaniment function, when playing VCD,
system detects external input and automatically screen to human sound signal in the disc, while
only saves sound accompaniment.
DK1010S
has the function of radio reception, and can also receive RDS signal. The radio head
control lines CE, DI, CL and DO are controlled by 28 array lines connecting to MT1389 control.
