Circuit Description - Pioneer RS-K1 Service Manual

13. CIRCUIT DESCRIPTION
13.1 A/D CONVERTER SECTION
@ As concerns the 18-bit A/D converter (IC701:
AK5369-VS)
The difference in performance when compared with
the formerly used 16-bit A/D converter is shown
below:
?
FSR
FSR
16-bit A/D converter = a)
ee
nner
FSR FSR
18-bit A/D converter=
a
Oa
FSR (Full Scale Range) = Input voltage range
The above shows that the quantization for the 18-bit
A/D converter is finer than that for the 16-bit A/D
converter by about four times.
# 16bit
Analog waveform
{raw acoustic sound)
Quantization
data
Sampling (44.1 kHz)
Quantization (65,536 divisions)
4% 18bit
Analog waveform
(raw acoustic sound)
al
Sampling (44.1 kHz)
Quantization (262,144 divisions)
As indicated by the graphs shown above, the 18-bit A/D
converter can produce sounds more similar to raw
acoustic sound.
By data comparison, THD (Vin = +FS, f = 1 kHz) for the
16-bit converter is 0.002% and THD for the 18-bit
converter is 0.0015%. This also indicates that sounds
gained by the 18-bit A/D converter is more similar to
raw acoustic sound than those obtained using the 16-bit
converter.
THD= Total Harmonic Distortion: ratio of effective
values of signals to effective values of harmonic
waves.
@ AK5369-VK
AK5369-VK is a 2-channel A/D converter using the
4-degree A> method. It has two built-in AS-
converters and allows simultaneous sampling of
analog input signals at a sampling rate of 64 times
(64 fs). Over-sampled data are decimated to 18-bit
data of fs by a digital filter.
13.2 OPERATIONAL AMPLIFIER WITH
A SWITCH
(IC451, 452: BA3129F)
@ Formerly used method
In the former type, switching of each source signal
was done by using one of the following methods:
1. A resistance mixing method is applied by making
use of operational amplifiers. Signal lines not
being selected are muted by means of transistors.
2. Level setting for each signal line is done by using a
discrete operational amplifier and then switching is
done by an analog switch.
@ Drawbacks of using the former methods
1. Signal lines not being selected must be muted. In
most cases, muting means is provided by
transistors. These transistors may cause distortion
to grow.
Source 1
Mute 1 Output
Source 2
Mute 2
a2
(Reference: THD for the analog switch (TC4066) is
0.1%.)
Satan