Onkyo A-8690 - Page 4

A-8690
4. DAC block adjustment
1) Confirmation of fs display
(1) Input a digital signal to one of the DIGITAL input terminals (1-3).
(2) The indicator LED should light as follows according to the sampling frequency of the input signal.
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2) Distortion adjustment
(1) Preparations
m™ Connect the digital output terminal of a suitable equipped CD player to the DIGITAL 1 digital input terminal
of the A-8690.
@ Connect a distortion meter to the analog output of circuit board NADC-3386 or to the unit’s analog REC OUT terminal.
M@ Input the distortion meter signal output and the distortion output to dual-phenomenon oscilloscope.
(2) Turn power ON to the unit.
(3) Play track 2 of the test disc (YEDS-18).
(4) Adjusting the 4th bit.
Adjust semi-fixed resistor R815 (R816) so that the non-continuous portion (difference in level) of the distortion
elements shown at right is as small as possible.
Distortion elements
Signal
™e Representative un-adjusted waveform
‘ea
The place to watch when
adjusting the 4th bit
(5) Adjusting the 3rd bit.
As with (3) above, adjust semi-fixed resistor R813 (R-814) so that the non-continuous portion (difference in level)
of the distortion elements is as small as possible.
wy,
The place to watch when
adjusting the 3rd bit
(6) Adjusting the 2nd bit.
As above, adjust semi-fixed resistor R811 (R 812) so that the non-continuous portion (difference in level) of the
distortion elements is as small as possible.
Note) It does not matter is up to this point the level of overall distortion is high.
The place to watch when
adjusting the 2nd bit