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AMPLUS 50
User Manual
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Schematic
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BOSE AMPLUS 50, AMPLUS 100 Schematic

CONTENTS
Safety Information............................................................................................................................ 3
Electrostatic Discharge Sensitive (ESDS) Device Handling ........................................................ 4
Warranty Information....................................................................................................................... 4
Table 1. Amplifier Comparison Chart................................................................................................4
AmPlus™ 100 Amplifier Specifications ......................................................................................... 5
AmPlus 50 Amplifier Specifications............................................................................................... 6
AmPlus 100 Theory of Operation .............................................................................................. 7-10
AmPlus 50 Theory of Operation ................................................................................................... 11
AmPlus 100 Amplifier Controls................................................................................................ 14-15
AmPlus 50 Amplifier Controls....................................................................................................... 16
Disassembly/Assembly Procedures ....................................................................................... 17-18
AmPlus 100 Test Setup Parameters............................................................................................. 21
AmPlus 100 Test Procedures................................................................................................... 22-25
Table 6. Source Input to 4Ω Speaker Outputs ............................................................................... 24
AmPlus 50 Test Setup Parameters ............................................................................................... 26
AmPlus 50 Test Procedures .....................................................................................................27-30
Table 12. Source Inputs to 4Ω Speaker Output ............................................................................. 29
Installation Diagram Notes:........................................................................................................... 31
Figure 7. AmPlus 100 70/100 Volt Mode/Model 1B Acoustimass
Part List Notes................................................................................................................................ 37
Main Part List AmPlus 100 Amplifier (see Figure 10) ................................................................. 38
Main Part List AmPlus 50 Amplifier (see Figure 11).................................................................... 40
Electrical Part List..................................................................................................................... 42-46
Resistors ................................................................................................................................... 42-43
Capacitors ................................................................................................................................. 43-44
Miscellaneous ........................................................................................................................... 45-46
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Bass Module Installation......... 34
1
CONTENTS
This service manual has been updated with information from supplement 194101-S1. This affects part numbers for C610 and C611.
AmPlus™ 50 and 100 Accessory Notes....................................................................................... 47
Packing List Power Amplifier Accessory Kit (see Figure 12) .................................................... 48
Part List Remote Volume Control (see Figure 13)....................................................................... 49
Packing List AmPlus 50 and 100 Amplifier (see Figure 14) ....................................................... 50
Part List AmPlus 100 Amplifier Accessory Transformer (see Figure 15).................................. 51
Part List AmPlus 50 and 100 Amplifier Rack Mount Accessory Kit (see Figure 16) ................ 52
Device Pin-out Diagrams.......................................................................................................... 53-57
Troubleshooting Tips..................................................................................................................... 58
CAUTION: THE AMPLUS 100 AND AMPLUS 50 AMPLIFIERS CONTAIN
NO USER SERVICEABLE PARTS. TO PREVENT WARRANTY INFRACTIONS, REFER SERVICING TO WARRANTY SERVICE STATIONS 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.
2
SAFETY INFORMATION
1. Parts that have special safety characteristics are identified by the symbol on schematics or by special notes on the parts list. Use only replacement parts that have
critical characteristics recommended by the manufacturer.
2. Make leakage current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit before returning the unit to the customer. Use the following checks to perform these measurements:
A. Leakage Current Hot Check
(1) With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. Do not use an isolation transformer during this test. Use a leakage current tester or a metering system that complies with American National Standards Institute (ANSI) C101. "Leakage Current for Appliances" and Underwriters Laboratories (UL) 1492 (71).
(2) With the unit AC switch first in the ON position and then in the OFF position,
measure from a known earth ground (metal water pipe, conduit, etc.) to all exposed metal parts of the unit (antennas, handle bracket, metal cabinet, screwheads, metallic overlays, control shafts, etc.), especially any exposed
metal parts that offer an electrical return path to the chassis.
(3) Any current measured must not exceed 0.5 milliamp.
(4) Reverse the unit power cord plug in the outlet and repeat test.
ANY MEASUREMENTS NOT WITHIN THE LIMITS SPECIFIED HEREIN
INDICATE A POTENTIAL SHOCK HAZARD THAT MUST BE ELIMINATED
BEFORE RETURNING THE UNIT TO THE CUSTOMER.
B. Insulation Resistance Test Cold Check
(1) Unplug the power supply and connect a jumper wire between the two prongs of the plug.
(2) Turn on the power switch of the unit.
(3) Measure the resistance with an ohmmeter between the jumpered AC plug
and each exposed metallic cabinet part on the unit. When the exposed metallic part has a return path to the chassis, the reading should be
between 1 and 5.2 Megohms. When there is no return path to the chassis, the reading must be "infinite". If it is not within the limits specified, there is the possibility of a shock hazard, and the unit must be repaired and rechecked before it is returned to the customer.
3
ELECTROSTATIC DISCHARGE SENSITIVE
(ESDS) DEVICE HANDLING
This unit contains ESDS devices. We recommend the following procedures 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.
WARRANTY INFORMATION
The following products are covered by a 5-year transferable limited warranty.
• Bose
• Equalizer Card
• Optional Opti-Voice
• Optional Source Input expansion card
®
AmPlus™ 100 and AmPlus 50
®
Page card
Table 1. Amplifier Comparison Chart
Features AmPlus 100 AmPlus 50
Inputs (balanced) 2 2 Line Outputs (balanced) 2 None Outputs
-Channel 1
-Channel 2
-70V Option Cards
-Opti-Voice® Page Card
-Opti-Source™ Card
-EQ Cards (various)
65 Watts 65 Watts
100 Watts
Yes Yes
Yes, 2
70 Watts
None
50 Watts
Yes, 1
No No
4
AMPLUS™ 100 AMPLIFIER SPECIFICATIONS
Power Output
Stereo: 65W per channel into 4Ω
50W per channel into 8Ω
70V bridged mono: 100W into 98Ω
Ω: 50W @ 70V output into 98Ω
70V/4
65W @ Ch2 output into 4Ω
Input Sensitivity
315mV required to drive both channels to full power in any mode.
Input Attenuation
0dB to -
∞
Input Impedance
32kΩ balanced, 11kΩ unbalanced
Line Output Impedance
600Ω
Line Output Distortion
≤0.2%
Frequency Response (active EQ bypassed)
4Ω output: 40Hz - 16kHz, ±1dB 70V output: 60Hz - 16kHz, ±1dB
Special Features
Remote volume control Turn on/off muting Clip detection and limiter Short circuit protection DC offset protection Thermal limiting Stable into reactive loads RFI protection UL and TUV approvals
Terminations
Inputs and outputs are quick-connect terminal blocks
Optional Accessories
EQ Cards (Model 1B, Models 8 and 25/32) Source Card Page Card
Operating Temperature Range (passively cooled)
12˚F to 120˚F (-10˚C to +50˚C)
AC Power Consumption
350 Watts max, 100/120Vac, 50-60Hz 350 Watts max, 220/240Vac, 50-60Hz
THD@ Rated Power
4Ω output: ≤2% THD (40Hz - 16kHz) 70V output: ≤2% THD (60Hz - 16kHz)
Hum and Noise
Line output: 92dB Power amplifier output: 80dB below rated output with 4Ω load
Controls
Inputs 1 and 2, input attenuation, remote volume, bass adjust 1 and 2, Input Mode and Amplifier Mode switches.
LED Indicators
Power: front panel
Size (Desk Mount)
17"W x 10"D x 3 3/4"H (43.2 x 25.4 x 9.52 cm)
(Rack Mount, chassis supported)
19"W x 10"D x 3 3/4"H (48.3 x 25.4 x 9.52 cm)
Weight
25 lb (11.3 kg)
Associated Equipment
Rack mount kit Second zone transformer
5
AMPLUS™ 50 AMPLIFIER SPECIFICATIONS
Power Output
70V Mono: 50W into 98Ω
Ω Mode: 70W outputs into 4Ω
4
Input Sensitivity
315mV required to drive amplifier to full power in any mode.
Input Attenuation
0dB to -
∞
Input Impedance
32kΩ balanced, 11kΩ unbalanced
Input/Output Configurations
1. Mono into 4Ω load
2. Mono into 70V load
3. As an extension to the AmPlus 100 amplifier
Frequency Response (active EQ bypassed)
4Ω output: 40Hz - 16kHz, ±1 dB 70V output: 60Hz - 16kHz, ±1 dB
THD@ Rated Power
4Ω output: ≤2% THD (40Hz - 16kHz) 70V output: ≤2% THD (60Hz - 16kHz)
Hum and Noise
Power amplifier output: 80dB below rated output with 4Ω load
Controls
Inputs 1 and 2, input attenuation, remote volume, bass adjust affects bandwidth of 50Hz - 150Hz by 0 - 10dB, Amplifier Mode switches.
Special Features
Remote volume control Turn on/off muting Clip detection and limiter Short circuit protection DC offset protection Thermal limiting Stable into reactive loads RFI protection UL and TUV approvals
Terminations
Inputs and outputs are quick-connect terminal blocks
Optional Accessories
EQ cards (Model 1B, Models 8 and 25/32)
Operating Temperature Range (passively cooled)
12˚F to 120˚F (-10˚C to +50˚C)
AC Power Consumption
200 Watts max, 100/120Vac, 50-60Hz 200 Watts max, 220/240Vac, 50-60Hz
Size (Desk Mount)
17"W x 10"D x 3 3/4"H (43.2 x 25.4 x 9.52 cm)
(Rack Mount, chassis supported)
19"W x 10"D x 3 3/4"H (48.3 x 25.4 x 9.52 cm)
Weight
20 lb (9.1 kg)
LED Indicators
Power: front panel
Associated Equipment
Rack mount kit
6
AMPLUS™ 100 THEORY OF OPERATION
Introduction:
The AmPlus 100 Business Music Amplifier is a two channel amplifier intended for business music and other installed sound systems. Its two inputs pass through the Opti-Voice Opti-Source™ Option Cards and Equalizer cards, if they are installed. These cards expand the number of inputs and outputs of the basic AmPlus 100, adding special features of paging, source selection, and priority override.
Sheet 1 of 3
Refer to the AmPlus 100 schematic diagram, sheet 1 of 3 for the following information. Note: 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.
The Channel 1 and Channel 2 Inputs at J1 [D8] are the "A" inputs on the AmPlus 100 and accept line level sources. U100A [D7] and U101B [C7] are unity gain, differential input amplifiers, with inputs well protected against RF and ESD. Ch 2 coming from U101B can pass through S1 [D7], the Mono/Dual Mono/2-Ch switch, in the 2-Ch position. In other positions of S1, Ch 2 is ignored unless S7 [C7], the 2-Ch/Mixer switch, is in the Mixer position, in which case Ch 2 and Ch 1 are mixed in the proportion set by R1 and R2, the Ch 1 and Ch 2 gain trim switches. After buffers U106A/B, the Ch 1 and Ch 2 signals are presented to one of the two inputs of U102 [D6] and U103 [C6], op amps with a pair of input stages and a selector mechanism, acting as a selector switch. If no option card is in the #1 position at J2 [C7], U102/103 pass the Ch 1 and Ch 2 A input signals straight through; if either a source or a page option card is in the #1 slot at J2, its output will be selected to pass forward into the AmPlus 100 signal path.
If an option card is installed in the #1 slot at J2, then the Ch 1 and Ch 2 A input signals are sent to the option card, and will be processed on that option card and returned to the AmPlus 100 along with the other signals contributed by the option card. The switching action of U102/103 is controlled by the DC level on pin 1. Normally, with no option card in the #1 slot at J2, this pin is pulled high, but when an option card is in place it shorts J2-5, pulling U102/103 pin 1 toward ground.
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Page and
Continuing forward on Sheet 1, [coordinates 5D and 5C], the Ch 1 and Ch 2 signals encounter another pair of switched op amps, U104/105 and the option card #2 connector at J3 [C6]. Signal flow here is handled in the same manner as around option card #1: if no option card is installed in slot #2 at J3, the signals pass through; otherwise, they enter the option card and are processed along with that card's sources before being returned to the main AmPlus 100 signal path.
Equalizer cards can be placed in J9 [D5] (for Ch 1) and in J10 [C5] (for Ch 2). If there is no EQ card in J9, the output from U104 passes through the unity gain buffer U100B, but if there is an EQ card, it "overrides" the signal from U104, substituting equalized audio from the EQ card. A similar arrangement for Ch 2 uses U101C. Special switching in the Ch 2 path after U101C allows the use of a single EQ card in the J9 slot in the cases where the source is being handled in mono or dual mono (in dual mono, R3, the Zone 2 Trim, is engaged). When the switch S1 is in the Mono or Dual Mono position, the Ch 1 signal is taken through an inverting stage (U101A) and passed to the Ch 2 path. Inverting the signal phase for the CH2 output compensates for the fact that the connector for the Ch 1 output results in the Ch 1 speaker signal also being inverted. U105 provides this phase inversion for Ch 2 signals when S1 is in the two channel mode.
7
AMPLUS™ 100 THEORY OF OPERATION
Sheet 1 of 3 (continued)
Note that the U104/105 output is also taken directly, before the EQ card, to two of the volume control VCAs (U204A, D), for use as Line Outputs. U204B, C implement the volume control for the main CH1 and CH2 paths that will move forward in the AmPlus 100 itself.
U204 [C2] is a quad, current in /current out, voltage controlled amplifier. Sections U204A, D, pins 4 and 13, (line output) are controlled only by the remote volume control action, whereas sections U204B, C, pins 5 and 12, (main path) are also controlled, in an OR'd fashion, by the signals CLIP / SC1 [D1] and CLIP / SC2 [A1]. The CLIP / SC signals become active when the power amplifier is clipping and/or attempting to drive a short circuit. This reduces the volume control setting, preventing distortion when a user plays the system too loud, as well as reducing power dissipation when there is a short circuited load.
Connector J4 [A8] ties one or two 10K rheostat-connected remote volume control potentiometers into Q201/221, whose outputs are steered by S5 [B4] (1 Remote / 2 Remotes) into U200 A, B, C, D, [B, C3] which inverts and scales the voltages to the appropriate range needed to control the VCAs. U203A, B [B4] buffer the CLIP / SC signals and OR them into the appropriate sections of U204 via diodes D200, 203. J12 [A8] is reserved for a possible future level control option.
U201A, U202B [B / C1] are the line output buffers, whose outputs are passed through series R/shunt C elements for RFI management. At the junction of the resistors, FETs Q401, 403 [A, B6] provide a power-up/power-down mute so that equipment connected to the line outputs will not experience thumps or pops.
Sheet 2 of 3
Refer to the AmPlus 100 schematic diagram, sheet 2 of 3 for the following information. Sheet 2 concludes the processing of the Ch 1 and Ch 2 signals, preparing them for the
power amplifiers. Circuits on this sheet deal largely with dynamic EQ and switchable EQ, all directed toward the bass region. The CH1 signal (DYNEQ1) entering Sheet 2 [C8] is sent in parallel to five points. Two paths pass through S4 [D6], which selects HP Out (150Hz high pass filter off) or HP In (150Hz high pass filter in). Another path, through R4 [D8], Ch 1 Bass Boost Adjust (50-150Hz) and a bandpass filter, U300B [D5], determines how much bass boost will be present. The signals out of S4 and the bandpass filter are summed in U300A [C4], along with yet another equalized signal.
To develop Dynamic EQ (an equalization where the amount of bass boost applied varies inversely with the signal level), the DYNEQ1 signal [C8] is fed to circuits composed of U300D, Q300, Q301, Q302, U303, U300C, U302A, and U304. U300C, Q300, Q301, Q302 develop a current proportional to the rectified signal level. This current enters the control pin of U302A, a transconductance amplifier, whose output current is multiplied by its control current. U302A is in the negative feedback loop of U300D, which now passes the signal DYNEQ1 with a gain controlled inversely by its own level. At small signals, the gain is the highest. Next, the output of U300D passes through one of two bandpass filters, shaping the signal into a bass boost signal. U304 [C4] selects between two bandpass filters, one centered at 55Hz and appropriate for the Free Space Model 1B Acoustimass® Module, the other at 90Hz, appropriate for full range systems, such as the Model 8, Model 25 and Model 32 Loudspeakers.
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Switching to the 55Hz bandpass filter is automatically handled by sensing when a Model 1B EQ card has been inserted in the Ch 1 EQ card socket [J9 on sheet 1 at coordinates D5] (signal EQGND [D1, sheet 1, and B8, sheet 2] is shorted to ground by the Model 1B EQ card when it is plugged in).
8
AMPLUS™ 100 THEORY OF OPERATION
Sheet 2 of 3 (continued)
Finally, the bass boost signal from the dynamic EQ path rejoins the other signals, (the full range signal, high pass filtered if S4 is in the HP IN position, via S4 and R381, and the manually adjusted bass boost signal via R4 and U300B) in the summing stage U300A [C4]. Now, at last, the Ch 1 and Ch 2 signals are ready to enter the power amplifiers, via connectors J7B [D1] and J8B [B1]. Note that Ch 2 is handled identically by the companion circuits shown below Ch 1's circuits.
Connectors J7B / J8B send the power amplifier power rails (±20V and ±40V) as well as ±12V power and various grounds. The CLIP / SC signals are returned from the power amplifiers via these connectors as well.
DC Offset detection circuits
Circuits that watch for excessive DC offsets of the power amplifier outputs are seen at coordinates C1. Ultimately, these circuits control the operation of relay K600 [sheet 3, B4] whose contacts enable the ±40V supply relays when K600 is energized. The op amp circuits U700 and U701 [sheet 2, C2] watch the Ch 1 and Ch 2 power amplifier outputs for DC offsets greater than about 2.4V. However, in order to keep the relay energized, other conditions must also be met. The ±40V rails and the ±12V rails must each be within a certain degree of symmetry. The Ch 1 power amplifier output is low pass filtered to pass only the DC offset component and is full wave rectified in U700B [C1] and U701A [C2]. A derived center tap from the ±40V supplies is also brought into the full wave rectifier B600 [sheet 3, B4]. The rectifier output is then compared to -2.4V in U701A [sheet 2, C2] (an op amp used as a comparator). If the absolute value of the offset is less than 2.4V, U701A's output is high, which holds Q700 off. Q700 off ensures that Q600 / 601 [sheet 3, B2] can be on, which allows current to flow through the K600 relay coil, energizing it, and thus allowing ±40V to be applied to the power amplifiers.
At coordinates [A, B 1, 2] on Sheet 2 of 3, the power amplifier output wiring is detailed. The power amplifier outputs are always tied to the Ch 1, 2 ± output connector pins, whether the amplifier mode switch S6 [A2] is in the Bridged or the 2 Channel position. However, if S6 is in the Bridged position and if a jumper has been placed between the two XFR CT pins, then the Ch 1 signal and the Ch 2 signals drive the output transformer primary in concert, potentially delivering in excess of 100 watts to the 70 / 100V output pins. Jumpers J409, 410 [sheet 2, A1] select between 70V and 100V operation.
Sheet 3 of 3
Refer to the AmPlus 100 schematic diagram, sheet 3 of 3 for the following information. Sheet 3 outlines the power amplifier and power supply circuits. Channel 1 circuitry is
explained below, Channel 2 operation is identical. The Ch 1 amplifier is built around a power amplifier IC, U500 [C6], augmented by class G transistors. For U500 audio output levels between about ±20V, U500 acts on its own, with its power coming from the ±20V rails via D502 / 509 [C, D5]. When the input signal rises, demanding an output in excess of about ±20V, transistors Q500, 501, 502 (positive rail) and Q503, 504, 505 (negative rail) come into play. Each of these transistor trios is driven by the input signal, via steering diodes D501, 507, and turn on as the higher signal peaks dictate. When Q502 is on, it handles part of the power dissipation by passing the loudspeaker current through power devices in series with the U500 rails. This allows U500 to deliver higher voltage, higher current power to its load while still staying within acceptable IC power dissipation limits. For those portions of the audio output waveform greater than about ±20V, the class G power transistors Q502, Q505 dissipate part of the power.
9
AMPLUS™ 100 THEORY OF OPERATION
Sheet 3 of 3 (continued)
The power amplifier is equipped with a clip detector circuit, implemented with U503 [D7], an LM311 comparator, and associated parts. The comparator watches the differential input voltage at the power amplifier input pins and compares it to 120mV. If the power amplifier, a feedback amplifier, is for any reason unable to deliver the output voltage requested by the source, linear operation ceases and an error voltage develops across its input pins. Inability to deliver the requested output voltage can occur if there is a short circuit on the amplifier output, a DC offset from some kinds of failures, or from overdriving the amplifier. Whatever the cause, if the input error voltage exceeds the threshold, the LM311 output will go low, toward the -12V supply. Active (low-going) CLIP / SC signals are fed through J7 pin 12 back to the VCA volume control IC, U204 on Sheet 1 [C2], where they turn the gain down to eliminate the stress of the overload situation. If the power amplifier starts to clip, the feedback signal acts as a limiter to keep the amplifier out of the distorted clipping region.
The AmPlus 100 power supply can be configured for either 120V (60Hz) or 230V (50 or 60Hz) AC mains by the appropriate placement of jumpers J603, J605, J606. This is shown on Sheet 3 at coordinates A6, 7, and 8. The AC mains voltage is stepped down and rectified, creating unregulated ±40V and ±20V rail pairs for use by the power amplifier. Regulators U600, 601 [A3] derive ±12V from the ±20V supplies for use by the op amp circuits. The bridge rectifiers B600, and B601 are fused against overload, while the ±12V supply is fused by 1/4 watt resistors R602, and R603. Also on Sheet 3, [B2], are Q600 and Q601, the relay drive transistors controlled by RELAY, from Sheet 2.
10
AMPLUS™ 50 THEORY OF OPERATION
Introduction:
The AmPlus 50 Business Music Amplifier is a single channel amplifier in most ways identical to the AmPlus 100. Both amplifiers are built in similar chassis using the same PCBs, but most of the Ch 2 parts are omitted in AmpPlus 50.
Note: Refer to the appropriate AmPlus 50 Schematic diagram sheet as indicated below for the following information.
Note: The designators inside the brackets “[ ]” are the schematic grid coordinates which are provided to make it easier to locate components on the schematic sheet indicated in the description.
Note: The components not used in the AmPlus 50 Amplifier are indicated on the schematic diagram as optional (opt).
Sheet 1 of 3
The discussion for the AmPlus 100 applies to the AmPlus 50, with a few exceptions. The Ch 1 and Ch 2 at J1[D8] inputs are summed after their input buffers U100 and U101 [C/D7] and are passed through the Ch 1 path. There are no connectors or slots for the #1 [J2] or #2 [J3] option cards, nor for the Ch 2 EQ card [J10]. There are no line outputs, and only one remote volume control input [J4]. Only the DYNEQ 1 output signal from Sheet 1 passes to Sheet 2. Only the CLIP / SC1 signal is passed into Sheet 1.
Sheet 2 of 3
The discussion for the AmPlus 100 applies to the AmPlus 50, with a few exceptions. Only the Ch 1 path of dynamic and fixed EQ circuits is populated, and only the Ch 1 power amplifier connector is provided. The output connector provides either 4 ohm or 70/100V CV, (Constant Voltage) outputs, as selected by S6 for Ch 1.
Sheet 3 of 3
The AmPlus 50 version is identical except that only the Ch 1 power amplifier module is installed.
11
(R5)
Gain
Ch. 2
Bass
(R4)
Gain
Ch. 1
Bass
(S4)
Filter
Switch
Pass
High-
Channel 2
Input
J1
section1 of 2
Switch (S1)
Input Mode
Mono
Channel 1
Input
Bass Boost
+ -
70V
Figure 1. AmPlus™ 100 Amplifier Block Diagram
+ -
CH. 1
Amplifier
Outputs
J6
CH. 2
CT
Power
+ -
XFMR
Dynamic
EQ
2 Ch.
Bass Boost
Power Amp 2
70V Bridged
Switch
(S6)
EQ
Mode
Amp.
Dynamic
Power Amp 1
2 Ch.
High Pass
Filter
70V Bridged
Level (R2)
Ch. 2
2 Ch.
(S7)
2-Ch.
Option Card 1
Channel 2
Option Card 2
Channel 2
EQ Card 2
Mono
Dual
Switch
Mix
Mixer
Trim (R3)
Zone 2
Option Card 1
Channel 1
Option Card 2
Channel 1
EQ Card 1
Level (R1)
Ch. 1
Remote
Zone 2
Control 2
VCA
2 Remotes
Remote
Zone 1
Assign Switch (S5)
Control 1
Remote Zone
VCA
1 Remote
12
VCA 2
2 Ch.
Switch (S1)
Section 2 of 2
Ch. 2
Mono
Dual
Mono
Input Mode
Ch. 1
J5
VCA 1
Line Outputs
(R4)
Ch.1
Gain
Bass
(S4)
Filter
Switch
Pass
High
Channel 2
Input
J1
Channel 1
Input
Power
Amplifier
Outputs
Figure 2. AmPlus™ 50 Amplifier Block Diagram
+ -
70V
J6
+ -
Ch. 1
70V
Bass Boost
4 Ohm
(S6)
Switch
Mode
Dynamic
EQ
Amp
High Pass
Filter
Power Amp 1
70V
4 Ohm
Level (R2)
Ch. 2
Level (R1)
Ch. 1
EQ Card
13
Remote
Zone 1
Control 1
VCA
VCA
AMPLUS™ 100 AMPLIFIER CONTROLS
INPUTS A
Ch1 Ch2
+- +-
2Ch
INPUT
MODE
dual mono mono
LEVEL
Zone 2Ch2Ch1
-6 -6 -6
-10-10 -10
0 0 0-40 dB -40 dB -40 dB
BASS
LEVEL
Ch2Ch1
+10
OFF
OFF
+10
REMOTE VOLUME
ZONE 1 ZONE 2
LINE OUTPUT
ZONE 1 ZONE 2
+-+-
POWER AMPLIFIER
70V ZONE1
4-16
ZONE 2 4-16
Ω
Ω
+-+-+-
XFR
CT
Inputs - The amplifier comes with two balanced inputs. They can be left and right channels from a stereo source or two distinct monophonic (mono) sources for 2 - zone applications. Two mono sources can also be mixed for single zone applications.
Input Mode - This switch determines how the Channel 1 and Channel 2 inputs are presented to the power amplifier section of the AmPlus 100. There are 3 possible modes.
1. 2 - Channel/Mixer - the inputs remain separate, not summed. Channel 1 and Channel 2 level potentiometers are active in this mode. Use this mode for:
a. Stereo (2 - channel). b. Two distinct sources in a two zone application (2 - channel), 1 source per zone. c. Two distinct sources in a single bridged mono zone (Mix).
MODE
70/100V 2 Ch BRIDGED
Note: In Mix mode both sources, Channel 1 and Channel 2, are presented to the amplifier simultaneously. When the internal source mix switch is in the MIX position, the Channel 1 attenuation controls the source connected to the Channel 1 input. The Channel 2 attenuation controls the source connected to the Channel 2 input.
2. Dual Mono - The Channel 1 and Channel 2 inputs are summed to mono and presented to the power amplifiers as two mono signals. This mode may also be used when driving a 70V
®
load from the Channel 1 amplifier outputs and a Bose
Model 1B Acoustimass® Bass Module
from the 4Ω Channel 2 outputs - see zone 2 level adjust.
3. Mono Mode - Both inputs, Channel 1 and Channel 2, are summed to mono. Only the Channel 1 level pot is active.
Level - Channel 1 level adjust - In 2 - channel (stereo) mode, this pot affects the signal level at the channel 1 low impedance (4Ω) outputs. In dual mono mode, it controls the zone 1 level. In mono mode, it controls the level of all inputs.
Channel 2 level adjust - In 2-Channel (stereo) mode, this pot controls the signal level at the channel 2 low impedance (4Ω) outputs. This pot is not active in dual mono or mono modes.
Zone 2 level adjust - This pot is only active when the input mode is dual mono. In this mode, this pot controls the signal level at the channel 2 low impedance outputs. This pot is a slave to the channel 1 pot; that is, the channel 1 pot controls the level of both zones in a 2-zone system. However, the zone 2 pot can be used to fine-tune the bass level when using the AmPlus 100 to drive a 70V load connected to the 70V output and a Model 1B Acoustimass Bass Module connected to the channel 2 output. This pot may also be used to fine-tune the bass level when using the AmPlus 100 to drive a 70V load connected to the 70V output and a Model 1B Acoustimass Module connected to the channel 2 output.
14
AMPLUS™ 100 AMPLIFIER CONTROLS
INPUTS A
Ch1 Ch2
+- +-
2Ch
INPUT MODE
dual mono mono
LEVEL
Zone 2Ch2Ch1
-6 -6 -6
-10-10 -10
0 0 0-40 dB -40 dB -40 dB
BASS
LEVEL
Ch2Ch1
+10
OFF
OFF
+10
REMOTE VOLUME
ZONE 1 ZONE 2
LINE OUTPUT
ZONE 1 ZONE 2
+-+-
POWER AMPLIFIER
70V ZONE1
4-16
ZONE 2 4-16
ΩΩ
+-+-+-
XFR
CT
70/100V 2 Ch BRIDGED
Bass Level - Use the bass level pots to increase the output level between 50 Hz and 150 Hz. This is useful for compensating for poor bass cabinet loading or high levels of low-frequency ambient noise. The channel 1 and channel 2 pots are active in all modes of operation.
Remote Volume - When using the amplifier to power one listening zone, connect the remote control unit to the zone 1 (+) pin and the ground pin and set the internal remote volume switch (see figure below) to 1 REMOTE. When using the AmPlus 100 for 2 - zone applications, connect a second remote to the zone 2 (+) pin and the ground pin and set the internal remote volume switch to 2 REMOTES.
High Pass
Mix
EQ 1
Filter
MODE
EQ 2
1 Remote
C
2 Remote
Line Outputs - Both line output responses are flat (regardless of whether or not you have installed active equalizer cards). The remote volume control affects the line output levels. Both outputs are active in stereo mode. Only zone 1 is active in dual mono and mono modes.
Power Amplifier Outputs - The 70V output becomes active when the amp mode switch is in the 70V position. In this setup, both AmPlus 100 channels are bridged and provide up to 100 Watts to the 70V speakers.
- When the amp mode switch is in the 2-Channel position and a jumper is placed across the Xfr. ct. pins, 50 Watts is available at the 70V output and 65 Watts is available at the channel 2 output. (see illustration at top of page)
- With the amp mode switch in the 2-Channel position, both channel 1 and channel 2 supply 65 Watts into a minimum load of 4Ω.
Internal High Pass Switch - When this switch is in the HPF ON position, frequencies below 150Hz are attenuated at 18dB/Oct. This low frequency roll-off occurs on Channel 1 only. Use this switch for bandlimiting high frequency speakers connected to channel 1 in a bi-amplified system. For example, the 70V/Model 1B system in Figure 7.
Internal Remote Volume Switch - For one zone applications, this switch should be in the 1 REMOTE position. For two zone applications, this switch should be in the 2 REMOTES position.
15
AMPLUS™ 50 AMPLIFIER CONTROLS
INPUTS A
Ch1
Ch2
+- +-
LEVEL
-6 -6
-10-10
0 0-40 dB -40 dB
BASS
OFF
GAIN
+10
Ch2Ch1
REMOTE VOLUME
POWER AMPLIFIER
70V
4-16
Ω
+-+-
Inputs - The AmPlus 50 amplifier comes with two balanced inputs. They can be left or right. Two mono sources can also be mixed. Since the AmPlus 50 is a single channel amplifier, a stereo source is internally summed to mono.
Level - Channel 1 level adjust - This potentiometer controls the signal level of the channel 1 input source.
Channel 2 level adjust - This potentiometer controls the signal level of the channel 2 input source.
Bass Gain - Use the bass gain pot to increase the output level between 50 Hz and 150 Hz. This is useful for compensating for poor bass cabinet loading or high levels of low frequency ambient noise.
Remote Volume - Connect the remote volume control unit to the zone 1 (+) pin and the ground pin to control the overall level of the amplifier remotely.
MODE
70/100V 4-16
High Pass
Filter
EQ 1
C
Power Amplifier Outputs - The 70V output is active when the amplifier Mode Switch is in the 70V position. The 4Ω output is active when the amplifier Mode Switch is in the 4Ω position.
Internal High Pass Filter Switch - When this switch is in the HPF ON position, frequencies below 150 Hz are attenuated at 18dB/Oct. Use this switch for bandlimiting high frequency speakers in a bi-amplified system.
16
DISASSEMBLY/ASSEMBLY PROCEDURES
1. Top Cover Removal
Note: Refer to Figures 3 and 4, as
applicable, for the following procedures. Note: The numbers in the parentheses
correspond to the callouts in Figures 3 and 4.
1.1 Unplug the power cable from IEC connector on the rear of the amplifier.
1.2 Using a phillips-head screwdriver, remove the five screws (1) that secure the top cover (2) to the amplifier chassis (16).
1.3 Lift the top cover straight off.
2. Top Cover Replacement
2.1 Observing orientation, place the top
cover (2) straight down onto the amplifier chassis (16).
2.2 Using a phillips-head screwdriver, secure the top cover to the amplifier chassis using the five screws (1) that were removed in procedure 1.
3. Main PCB Removal
4. Main PCB Replacement
4.1 Orient the main PCB (8) so that the
connectors are aligned with the rear panel of the amplifier chassis (16), and slide the main PCB into place.
4.2 Secure the main PCB to the amplifier chassis using the six screws (9) removed in procedure 3.4.
4.3 Reconnect all connectors unplugged in procedures 3.2 and 3.3.
4.4 Replace the top cover (2) using procedure 2.
5. Amplifier Module Removal
5.1 Remove the top cover (2) using
procedure 1.
5.2 Unplug the appropriate cable connector, (J7B or J8B), for the amplifier module that you wish to remove.
5.3 Remove the two screws (12) that secure the amplifier module to the amplifier chassis (16) and lift the amplifier module straight out.
3.1 Remove the top cover (2) using procedure 1.
3.2 Unplug all of the cable connectors from the rear panel of the amplifier.
3.3 On the main PCB (8), unplug the connectors at J2, J7B, J3, J8B, J602, J601, J400, J401, and J600.
3.4 Using a phillips-head screwdriver, remove the six screws (9) that secure the main PCB to the amplifier chassis (16).
3.5 Lift the main PCB at the edge nearest the amplifier heatsinks, and slide the PCB forward, until the main PCB connectors clear the amplifier rear panel, then lift the PCB straight up.
6. Amplifier Module Replacement
6.1 Place the amplifier module into the
appropriate spot in the amplifier chassis (16) and secure it using the two screws (12) removed in procedure 5.3.
6.2 Plug the amplifier module cable into the appropriate connector (J7B or J8B) on the main PCB (8).
6.3 Replace the top cover (2) using procedure 2.
17
DISASSEMBLY/ASSEMBLY PROCEDURES
7. Power Transformer Removal
7.1 Remove the top cover (2) using
procedure 1.
7.2 Unplug the transformer cables at J601 and J602 on the main PCB (8).
7.3 Remove the four nuts (5) that secure the power transformer (7) to the amplifier chassis (16).
7.4 Lift the power transformer straight out of the amplifier chassis.
8. Power Transformer Replacement
8.1 Place the power transformer (7) into the
amplifier chassis (16), aligning it over the chassis studs.
8.2 Secure the power transformer to the amplifier chassis using the four nuts (5) removed in procedure 7.3.
10. Audio Transformer Replacement
10.1 Place the audio transformer (3) into
the amplifier chassis (16) with the wires facing toward the main PCB (8), aligning it over the amplifier chassis studs.
10.2 Secure the audio transformer to the amplifier chassis using the two nuts (5) removed in procedure 9.3.
10.3 Plug the audio transformer cables into the main PCB at J400 and J401.
10.4 Replace the top cover (2) using procedure 2.
8.3 Plug the power transformer cables into J601 and J602 on the main PCB (8).
8.4 Replace the top cover (2) using procedure 2.
9. Audio Transformer Removal
9.1 Remove the top cover (2) using
procedure 1.
9.2 Unplug the audio transformer (3) cables from the main PCB (8) at J400 and J401.
9.3 Remove the two nuts (5) that secure the audio transformer to the amplifier chassis (16).
9.4 Lift the audio transformer straight out of the amplifier chassis.
18
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