Pioneer RS-K1 Service Manual page 79

Source 1
Output
Source 2
Analog switch
(semiconductor)
@ Advantages of the OPERATIONAL AMPLIFIER with
1.
a switch that is just adapted
Because a switch is built in the amplifier, it is
unnecessary to use a transistor for muting. This can
prevent distortion from growing. Because a single
operational amplifier is used for each source, level
setting for each source can be done without
affecting the sound quality.
The entire THD in the section of an operational
amplifier plus a switch is 0.0015%, which is
significantly better.
Also, the use of one chip IC per 1 channel (the
former amp uses one chip IC per 2 channels) allows
the power supply and ground to be separated per
channel. This results in improvement in separation.
Source 1
Output
Source 2
Changeover Control
Operational amplifier with a switch for audio
Because the switch is contained in the NF loop,
deterioration of the distortion factor is eliminated.
13.3 + POWER SUPPLIES
@ Formerly used power supply
A single power supply was used and setting of a
supply voltage can be performed in the range of
normally 0 to 8 V when used in a car. Thus, a
dynamic range was determined within the above
range. There was a limit in improvement in S/N.
The reference voltage that took the role of a
temporary ground was needed. Signals were
amplified relative to this reference voltage, and thus
the reference voltage circuit had a large effect on
the sound quality.
In addition, because signal lines coupling capacitors
were needed, their effects were also present.
@ Power supply that is just adapted
The use of both the plus and minus power supplies
(+8 V) increases, in principle, a dynamic range by 6
dB as compared with the former power supply,
which results in improvement in S/N.
Moreover, because the reference voltage is
unnecessary, signals are amplified truly relative to
ground, and thus no deterioration occurs in the
sound quality.
in addition, there is a possibility of deleting coupling
capacitors, which may provide higher sound quality.
All signal circuits in this unit are operated by the
plus and minus power supplies, and there is no
capacitors in the section from the head to EQ amp
and in the section from MIX to A/D converter.
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