Bose 3-2-1GS Series II Посібник з усунення несправностей - Сторінка 12
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4.1 Analog Audio Path
4.1.1 Analog Input
There are total of 7 analog input sources: 6 external analog inputs and one internal analog
input. Those 6 external analog inputs are: 1 tuner from Tuner board via J6000 [sheet 13, D8],
3 external (AUX, CAB/SAT and TV) from connector J201 [sheet 10, B-D8], 2 network speaker
(Zone1 and Zone2) from J202 [sheet 11, C3] via differential input buffer U8406 [B/C1]. The
internal analog input is from the mix-down DAC U9200 [C8] which convert I2S audio stream
from the CS98200 to an analog signal which is one of the two inputs to the summing circuit
U9100 [C5].
The 6 external analog sources are selected by the TEA6422 (U4000 [sheet 10, B5]) analog
audio MUX. The MUX is controlled via the CS98200's I2C bus. The MUX has the ability to
direct any one of the 6 input sources to any one of the 3 output.
4.1.2 Analog Output
Only the 3rd output of the TEA6422 (U4000) analog audio MUX is used (the 1st and 2nd output
channels are unused) and the 3rd output of the TEA6422 is summed into the NJM4556 buffer
amplifiers (U9100 [sheet 11, C5]). The mix-down DAC outputs are also summed into these
buffer amplifiers. When one of the 6 external analog audio sources is selected as the console
analog output, the 3rd output of the TEA6422 is active and the output of the mix-down DAC is
placed into reset through the reset bit in the I2C registers in order to reduce the noise level to
minimum. In a similar way, when the CS98200-generated down-mix is selected as the console
analog output, the 3rd output of the TEA6422 is muted and the output of the mix-down DAC
takes active.
The analog output goes to the bass module via the connector J100 [sheet 10, B2]. The
TEA6422 analog input MUX supports 2Vrms signal levels. The maximum amplitude of the
differential outputs of the AK4382 DAC is approximately 2Vrms. External analog input signals
may be up to 2Vrms without experiencing distortion or clipping-- absolute maximum allowable
input levels are about 3dB higher.
4.2 Digital Audio Path
4.2.1 Digital Input
There are total of 6 digital input sources: 4 external digital inputs and 2 internal digital input.
Those 4 external digital inputs are: AUX, CABSAT and TV from connector J201 [sheet 12, C8]
and optical signal from J8000 [B8]. The 2 internal digital input sources are from the DVD ROM
driver via connector J3200 [sheet 7, B/C5] and hard disk driver (HDD installed on premium
product only) via connector J9341 [B/C4].
The 4 external digital sources are directed to the AK4112 U8001 [sheet 12, B/C5] SPDIF re-
ceiver. The SPDIF receiver is controlled via the CS98200's I2C bus. The 2 internal digital input
sources (both DVD ROM driver and HDD) feed the audio data streams to CS98200 via the
ATAPI bus for decoding and processing.
THEORY OF OPERATION
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