Bose FREESPACE BUSINESS Service Manual - Page 8

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The following discussion references the Main PCB Schematic and Block Diagram. The

schematic is located in the back of this manual and the block diagram is shown in Figure 3.

The FreeSpace™business music system electronics module powers the FreeSpace loud-

speaker system,which is a derivative of the AM-5

system, FreeSpace is meant to be used in conjunction with the customer's audio source.

The FreeSpace system offers the following features:

Automatic turn-on/ turn-off (audio sense or signal from the customer's audio source)

Automatic (Bose

Bi-amplification for better power distribution to speakers

High Efficiency Class G Power Amp stages (100W + 50W +50W)

Active equalization for smoother frequency response

Amplifier short-circuit protection

Bass/treble room compensation controls

Differential input stage (to reject hum)

Dynamic compressor to prevent amplifier output overload distortion

Electronic remote volume

Refer to the block diagram and schematic mentioned above. For discussion of L/R channels,

only the right channel is discussed. Left channel operation is identical.

1. Power Supply

Two power supplies are used in the FreeSpace system. One is a low power regulated ±15VDC

supply used to power the signal processing circuitry, the other is the high voltage main power

supply used to power the three Class G power amplifier stages. Two voltages are provided for

class G operation, ±20VDC and ±40VDC. The regulated ±15VDC supply always remains

energized as long as the unit is wired to an active mains voltage source. The main power

amplifier supply is turned on and off by the audio sensing circuit (discussed elsewhere).

THEORY OF OPERATION

patented) dynamic equalization

BLOCK DIAGRAM DESCRIPTION

GENERAL

powered loudspeaker system. As a powered