This PCB selects the analogue input for the main zone & Zone 2/3 and also
digitises the analogue input for processing by the DSP / transmission over
SPDIF.
One of seven phono inputs (Tape, CD, AV, DVD, SAT, VCR, PVR), Aux
(external) input (see L127), AM/FM & DAB(internal)/Sirius(external) inputs
(see L118), Net (internal) input (see L119) and Phono (see L117).
The input for the main zone is selected using IC200, IC208, IC205, IC209
(74HC4051D 8-1 mux) under the control of IC101 & IC102 (74HC595 serial to
parallel converter), controlled by AN SPI Data, AN SPI Clk & A In Mux Latch.
The muxes operate on the virtual earth of IC203 part A (left channel) & IC206
part A (right channel), both NJM2114 op amps, inverting the signal. Part B of
these two op amps re-invert the signal (correct phase) and this output is used
by the ADC & the direct path – Main L & Main R.
IC202 (NJM2114 op amp) inverts the original output of the mux (correct
phase) to provide the three tape outputs, Tape Out, PVR Out & VCR Out.
Each of these has individual mutes – IC201, IC204, IC207 (DG413DY
analogue mux) which mutes the output if that input is selected to prevent
feedback. Otherwise, the output is the selected input. The signals for these
mutes, /Tape Mute, /PVR Mute, /VCR Mute come from IC102 (74HC595
serial – parallel converter).
Selection of the Zone 2 input is very similar, using IC300, IC303, IC302,
IC304 (74HC4051 8-1 muxes) and IC301 (NJM2114 op amp).
The Main L & Main R are connected to input AIN1A/AIN1B of IC100 (CS5345
ADC). Aux L & Aux R are also connected to AIN4A/AIN4B as this is
configurable as the MIC input and can provide power from pin25 of IC100.
the ADC is controlled from the PW338 via AN SCL & AN SDA. ADC/RESET
also comes from IC102, so the ADC can be held in reset when not being
used.
The ADC always operates in slave mode and will sample at the rate dictated
by the incoming clocks from L115 (buffered on L122). ADC Data is sent to
L115 so that it can be transmitted by the SPDIF transmitter and selected for
input to the DSP.
+12VA (REG301 LM7812) & -12VA (REG304 LM7912) for the local op amps
are derived from +15V & -15V from L123.
+5VA (used by the ADC) is derived from the +12VA with REG302 (LM1117).
+3V3D (used by the ADC) is derived from the +12VA with REG300 (LM1117).
+3V3A (REG303 LM1117) & -3V3A (REG305 LM337LZ) for the muxes are
derived from +5VA & -12VA.
L116AY Analogue input board