ページを印刷するA-09
5. CIRCUIT DESCRIPTION
M@ PROTECTION CIRCUIT
In the A-09, in order to avoid inferior sound quality due to
the relay contact point, the relays that normally are serially
inserted to the signal line have been eliminated.
FUSE
VOLTAGE AMP
RY1
@ Sequence of RY1 and RY2 at the time of power ON/
OFF
Both RY1
and RY2 are commonly closed approximately 8
seconds after turning ON the power, and pop noise of the
voltage amplifier is muted by 100Q and attenuation by RY1,
the power amplifier's output impedance and the attenuation
by RY2 by a total of approximately 100dB. When turing
OFF the power, there is only a muting by 100Q and RY1
(Approximately —80dB), but as the pop noise of the power
supply of the voltage amplifier is very small when the power
is turned OFF, there is no problem in practical use.
The
upper
and lower
stages
of the power
amplifier are
totally symmetrical, and as the input is grounded by RY!
at
the time of power ON/OFF, there is no pop noise at ail.
@ Sequence
of RY1
and
RY2
at the time
of DC
detection
* Both RY1
and RY2 are commonly closed at the time of
DC detection. If DC still appears at the speaker terminal
in this condition, a current of the output voltage value
divided by the contact resistance value of RY2 will flow,
and the fuse (5A) on the primary side will melt.
- At the time of load short-circuit, RY1
and RY2 will not
operate together, but due to the output level of the source
equipment and the position of the attenuator of A-09, the
signal level of the speaker terminal will become
higher
(when the load short-circuit current become higher) and
the primary side fuse will melt.
56
Closed
RY2
Open
Closed
—-—-——-—
Muting time:
Approximately
8 seconds
Power ON
Power OFF
DC detection
Fuse melts