This PCB converts the digital audio from the DSP (see L156) to analogue
audio. It also configures the use of channels 6 & 7, has the headphone amp,
has the RIAA equaliser for the Phono input and handles the multi-channel
analogue input.
The phono amplifier is a standard RIAA response and is intended for use with
MM cartridges, 5mV (check this!) output. C128 & C129 are important to
prevent the DC offset of IC100 (NJM2114 op amp) from causing problems.
IC101 forms the basis of the headphone amplifier. The output of this section
goes to L127.
IC300 (CS4385 8-channel DAC) takes multichannel data (Data LR, Data
CSw, Data SlSr, Data SblSbr) from the DSP (L156) in addition to clocks (DAC
MClk, DAC BClk, DAC WClk) from L115 (buffered on L122). Control of the
DAC is via AN SDA, AN SCL (from the PW338) and DAC /RESET (from
IC212).
The balanced outputs from the DAC are filtered by IC400, IC401, IC402,
IC403 (NJM2114 op amps). All channels are identical except for the
subwoofer, which has 10dB (check this!) gain.
Left & right inputs to IC204 (CS3318 volume control) are multiplexed between
the filtered DAC output, the Main L & Main R direct analogue inputs (from
L116) and the left & right multichannel inputs (SKT200) with IC200
(74HC4052 dual 4-1 mux). This mux operates on the virtual earth of IC201
(NJM2114 op amp) and also provides the signals Mux L & Mux R.
The centre input to IC204 (CS3318 volume control) is multiplexed between
the filtered DAC output and the centre multichannel inputs (SKT200) with
IC203 (74HC4053 triple 2-1 mux). This mux operates on the virtual earth of
IC205 part A (NJM2114 op amp).
Subwoofer, surround left & surround right inputs to IC204 (CS3318 volume
control) are multiplexed between the filtered DAC output and the subwoofer,
surround left & surround right multichannel inputs (SKT200) with IC214
(74HC4053 triple 2-1 mux). This mux operates on the virtual earth of IC201
(NJM2114 op amp) part A (subwoofer) & IC207 (NJM2114 op amp - Surround
left & surround right).
IC213 selects between the filtered DAC output of surround back left / right,
surround back right / left multichannel inputs, Z2 L / Z2R and Mux L / Mux R.
This allows the use of channels 6 & 7 as either surround back left/right in the
main zone, or powered Zone 2 outputs, or bi-amped left/right in the main
zone. This mux operates on the virtual earth of IC209 (NJM2114 op amp).
IC204 (CS3318 volume control) is controlled by AN SCL, AN SDA (from the
PW338) and VOL /RESET & VOL /MUTE from IC212.
L117AY Analogue output
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