Bose 1600-VI Service Manual download pdf (Page 11)

THEORY OF OPERATION

2.1 Input Module

Note: Some amplifiers will be equipped with the Bose

ACM-1 Amplifier Control Module in

place of the Bose Input Module. This module retains all of the capabilities of the Bose Input

Module, except sequence (see section 2.8), and includes the ability to control and monitor the

amplifier over a control network. Refer to the ACM-1 Amplifier Control Module service manual,

part number 199746 for more information.

The Input Module consists of signal input connections, mode switching, optional equalization,

and power sequencing circuitry. The module operates from +15V and -15V, supplied by the

host amplifier through J2-2 and J2-1 respectively.

The signal inputs are designed for balanced connection, though unbalanced inputs can be

configured by proper input wiring. Channel 1 (CH1) line-level inputs are made via P4 and J4,

Channel 2 (CH2) input connections are made via P1 and J5. P4 and P1 allow for the insertion

of either male XLR or phone plugs. The phone plug terminations are: tip positive (+), ring

negative (-), and sleeve ground. The XLR connections pins 2 and 3 are user configurable. As

shipped, jumper blocks JB2 and JB1 have jumpers between pins 2 to 3 and 5 to 6. This jumper

configuration assigns XLR pin 2 to positive (+) and pin 3 to negative (-), pin 1 is ground in all

configurations. If the jumpers are placed across JB1/JB2 pins 1 to 2 and 4 to 5 the XLR pin

assignment becomes pin 2 negative (-), and pin 3 positive (+). The Euro-block terminal block

connectors J4 and J5 assignments are: pin 1 positive (+), pin 2 negative (-), and pin 3 ground.

The CH1 input signal is applied to ICs U1, and the CH2 signal to U2. U1 and U2 are unity gain

(0 dB) differential amplifiers (SSM2141). These inputs are protected against RFI (Radio

Frequency Interference) and ESD (Electro-Static Discharge). The signals are then routed to

the A inputs of op-amp/switch ICs (BA3128) U4 (CH1) and U3 (CH2) and to EQ card

connectors J6-4 and J7-4 respectively. The switch’s B inputs are driven by the output of the EQ

cards via J6-5 and J7-5.

The input module detects the presence of EQ cards via J7-6 and J6-6. Without the card

installed these pins are pulled high (+15V) which keeps both CH1 and CH2 sections of dual

LED D23 extinguished. This logic high signal is also applied to the control pins of the switch

ICs which selects the A (unequalized) input. When an EQ is plugged into J7 and/or J6 pin 6 the

EQ is detected and pulls the control pin low (+7.5V), turning on the corresponding LED(s) and

switching the IC to the B input which selects the output of the EQ card.

On some EQ cards the equalization can be modified for either full range “FULL BANDWIDTH”

or bi-amplified “HF ONLY” operation. The equalization mode switch SW2 selects either FULL

BANDWIDTH or HF ONLY modes of the EQ cards installed. These control signals are sent to

the EQ cards via J6-7, 8 and J7-7, 8.

The selected signals from U4 and U3 are buffered by U7B and U7A which are wired to P2 and

P3. These phone connectors provide balanced, buffered, equalized outputs (if an EQ card is

installed) to drive additional amplifiers or other equipment. This allows external equipment to

provide equalized signals without the need for additional equalization. The pin assignment for

these connectors are the same as for the input phone connectors P1B and P4B. The output

circuitry is also protected from RFI and EMI.

The amplifier can be operated in four different output modes: normal (two independent chan-

nels) dual mono (one input channel, two separate channels), bridged mono, or parallel mono.

These modes are selected via SW1 and control the operation of op-amp/switching ICs U6 and

U5. Parallel mono operation requires internal modifications to the amplifier, contact the local

Bose Pro Product dealer for information on parallel mono operation.

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Bose 1600-VI Service Manual Page 11

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