BOSE AMPLUS S7, 1800V S7 Schematic
FreeSpace® 360 Surface and In-ground
Loudspeaker EQ Cards
®
®
©
1998 Bose Corporation
Supplement
Part Number 181812-S7 Rev. 00
CONTENTS
Electrostatic Discharge Sensitive (ESDS) Device Handling ........................................................ 3
Supplement Description.................................................................................................................. 3
Warranty Information....................................................................................................................... 3
Theory of Operation......................................................................................................................... 4
Equalizer Card Curve Diagrams ..................................................................................................... 5
Figure 1. FreeSpace 360® Surface EQ Curve.................................................................................. 5
Figure 2. FreeSpace 360 In-Ground Soft Ground EQ Curve ........................................................... 5
Figure 3. FreeSpace 360 In-Ground Hard Ground EQ Curve.......................................................... 5
Test Procedures ............................................................................................................................ 6-7
Part List Notes.................................................................................................................................. 8
FreeSpace 360 EQ Card Part List .............................................................................................. 9-10
Packing List, FreeSpace 360 EQ card (see Figure 4).................................................................. 11
Figure 4. FreeSpace 360 EQ Card Packing View.......................................................................... 11
Figure 5. FreeSpace 360 Equalizer Board Topside and Etch Layout Diagram.............................. 12
Figure 6. FreeSpace 360 Equalizer Board SMD and Etch Layout Diagram .................................. 12
CAUTION: The FreeSpace 360 Equalizer Cards
contain no user serviceable parts. To prevent
warranty infractions, refer servicing to
warranty service centers or factory service.
PROPRIETARY INFORMATION
THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF
BOSE® CORPORATION WHICH IS BEING FURNISHED ONLY
FOR THE PURPOSE OF SERVICING THE IDENTIFIED BOSE
PRODUCT BY AN AUTHORIZED BOSE SERVICE CENTER OR
OWNER OF THE BOSE PRODUCT, AND SHALL NOT BE
REPRODUCED OR USED FOR ANY OTHER PURPOSE.
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ELECTROSTATIC DISCHARGE SENSITIVE
(ESDS) DEVICE HANDLING
This unit contains ESDS devices. We recommend the following precautions when repairing,
replacing, or transporting ESDS devices:
• Perform work at an electrically grounded work station.
• Wear wrist straps that connect to the station or heel straps that connect to conductive floor
mats.
• Avoid touching the leads or contacts of ESDS devices or PC boards even if properly
grounded. Handle boards by the edges only.
• Transport or store ESDS devices in ESD protective bags, bins, or totes. Do not insert
unprotected devices into materials such as plastic, polystyrene foam, clear plastic bags,
bubble wrap, or plastic trays.
SUPPLEMENT DESCRIPTION
This supplement should be used along with the 1800V EQ PCB service manual part number
181812-S2. The disassembly/assembly procedures, and packing part list should be used along
with the information in this manual. The test procedures were included in this manual for your
convenience.
WARRANTY INFORMATION
The FreeSpace® Model 360 Loudspeaker Equalizer Cards are covered by a 5-year
transferable limited warranty.
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THEORY OF OPERATION
These Equalizer cards are designed to be installed into the AmPlus™ 50 and 100 amplifiers
and the Bose® 1600 Series VI and 1800 Series V/VI amplifiers.
The FreeSpace® 360 loudspeaker requires equalization, and this equalization is a function of
the installation. There are two variants of the card that implement EQ curves for these
installation situations:
• In Ground (when the FreeSpace 360 loudspeaker is mounted in the ground).
The appropriate EQ curve for soft or hard ground is selected with a slide switch on the card.
When S1 is in the SOFT position, the Soft Ground EQ is used; when S1 is in the HARD
position, the Hard Ground EQ is used.
• In the Surface variant, S1 is omitted and jumpered to the SURFACE position.
Note: Refer to the FreeSpace 360 Surface or In-Ground schematic diagrams, as appropriate,
for the following explanation. The designators inside the brackets "[ ]" are the schematic grid
coordinates which are provided in order to make it easier to locate components on the
schematic sheet indicated in the description. Components shown on the schematic as
OPT (optional) are not used in that particular configuration.
The input signal is applied to these cards at JP1 pin 4. The first section at the input, U2-B [D7],
combines a first order high-pass filter with one section of a parametric cut filter. The parametric
is set for -15dB at 27Hz and provides a steep slope below about 80Hz. The equalization is
segmented, with one block (U2 and U1), all sections [D1-8] dedicated to bass region equalization. Following the output of this section, U2-A [D1], the signal is presented to two parallel
equalization paths, one comprised of U3 [B4-7], U4-B [C3], and dedicated to EQ for mounting
in soft ground of the FreeSpace 360 loudspeaker. The other path, comprised of U5 [B4-7],
U4-A [B3] provides equalization for the FreeSpace 360 loudspeaker in hard ground installations. In the case of the FreeSpace Surface EQ card, the bottom leg of the equalizer card is
not used.
The operation of all three equalizers is similar. Considering the bass equalizer, we see U2-B's
[D7] output passed through R8 [D7] and into the non-inverting input of U2-A [D2]. This input is
extended as a bus to which EQ sections Bass 1 [D6] and Bass 2 [D5] are connected. These
will introduce dips into the audio response to provide bass cut as required. Sections Bass 3
[D4] and Bass 4 [D3] are connected to a bus extended from the inverting input of U2-A [D2]
and provide bass boost.
See Figures 1,2 and 3 for the EQ curves for the various equalizer cards.
Each of the EQ sections utilizes a gyrator-connected op-amp in conjunction with a series
capacitance to simulate an LCR series tuned circuit. The values of the capacitors and resistors
are chosen to implement EQ dips and/or peaks at the appropriate frequency, amplitude and Q
to realize the desired EQ curves. On the In-Ground EQ card, S1 [B2] selects either the HARD
or the SOFT mount EQ curve.
The output signal is taken from JP1 pin 5, and returns to the amplifier. The equalizer cards are
sensed by the amplifiers as follows. In the AmPlus 50 and 100 amplifiers, Pin 12 of J1 [B2] is
grounded and is sensed by the dynamic EQ circuit on sheet 2 of the AmPlus 50 and 100
schematic diagrams. In the 1600/1800 amplifiers, 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). 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 will then select the output of the EQ card to be passed on to the amplifier.
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