Bose 3-2-1GS Series II Troubleshooting Manual - Page 20

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Bose 3-2-1GS Series II Troubleshooting Manual

2.1 Interface connector and cable descriptions

The 13-pin interface connector is wired in a one-to-one fashion with the console connector.

The pins/signals are as follows:

Pin Number

3,11

9,8

12,10

Shell

2.1.1 Smart Speaker

This is a single-wire 4800 baud, half duplex connection. It operates on an open-collector prin-

ciple and follows the hardware and software protocol defined by the SmartSpeaker interface

specifications. It operates similar to RS-232, but with a 0-3.3/5V level and positive logic.

2.1.2 MUTE Control

This is a positive logic control input to the Powered Speaker. Asserting this line (+3.3V) forces a

hardware mute of the power amplifiers. This input is internally pulled logic high in the Powered

Speaker and the input must be pulled to logic low by the console to allow audio to be heard.

2.1.3 S/PDIF

The S/PDIF input is a fully differential input which is terminated by a pair of back-to-back diodes

only. Supported sample rates are 44.1 kHz and 48 kHz.

2.1.4 Analog Audio Input

The analog audio inputs are fully differential with an input impedance of approximately 10k

ohms. The full scale input is 2.0Vrms.

2.1.5 DSP_SHUTDOWN

This is a positive logic control input which, when asserted logic high, shuts down the SMPS

feeding the entire DSP and signal processing path. It is not implemented (via depopulated

components) in the production design.

2.1.6 Vunreg

This is a DC supply which provides unregulated power for use by the console. Approx. 30W

peak is available from this supply. It is internally fused at 4A.

THEORY OF OPERATION

Signal Description

Vunreg

GND

SPDIF +/-

Mute

DSP_Shutdown

AGND

DGND

Audio Left +/-

Audio Right +/-

SmartSpeaker

SGND

Wire Type/Gauge

#20AWG

#28AWG twisted pair

#28AWG

#28AWG Drain/shield over Audio Right & Left

#28AWG Drain/ shield for SPDIF+/-

#28AWG twisted pair

#28AWG

Overall tin-copper braid shield