TOA NEW 900 SERIES
IN-WALL MIXER POWER AMPLIFIER
Models: W-906A, W-912A
General Description
The TOA W-906A and W-912A Mixer Power Amplifiers are designed to control and mix up to six independent input signals, with an option for two additional inputs via an expanding kit. The W-906A delivers up to 60 watts of output power, while the W-912A provides 120 watts. Optional accessory modules enhance versatility for various applications. Edge connectors on the front panel allow for the selection of TOA plug-in modules, including microphone preamplifiers, phono preamplifiers, auxiliary preamplifiers, bridging transformers, line matching transformers, paging inputs, and tone signal generators. Features include a muting function, remote input level control via an external potentiometer (with specific modules), a built-in one-octave graphic equalizer with 9 bands for sound tailoring and feedback reduction, and a built-in compressor circuit to protect output levels. The amplifiers offer output terminals for 4 or 8-ohm speaker systems, and 25 or 70-volt speaker distribution systems. Mounting can be flush in a four-inch wall using the BX-9F back box or surface mounted using the BX-9S back box. A key-locked hinged door provides protection against tampering.
Key Features
- 6-channel mixer power amplifier
- Expandable to 8-input
- Output power: 120W for W-912A, 60W for W-906A
- Wide frequency response: 30 to 20,000Hz ± 1dB
- Low distortion and noise
- Excellent output regulation
- Built-in one-octave equalizer
- Built-in compressor
- Self-protection circuitry design
- Separate output terminals: 4 and 8 ohms, 25 and 70 volts
- Extra space for customizing
- LED pilot light
- LED peak indicator
- Full range of plug-in modules
- Flush and surface mounting
Controls and Features
The front panel of the W-906A/W-912A features various controls and indicators:
| Item | Name | Function/Description |
|---|---|---|
| 1 | POWER SWITCH | Two-position push button switch for on-off modes. |
| 2 | INPUT VOLUME CONTROLS | Adjust gain of inputs #1 through #6 respectively. |
| 3 | MASTER VOLUME CONTROLS | Adjust overall gain of the unit. |
| 4 | MODULES (OPTION) | Select appropriate modules according to the application. |
| 5 | COMPRESSOR CONTROL (LIMITER) | Setting the control switch to OFF bypasses the compressor circuit. Turning it clockwise reduces the limiter level (limits output). |
| 6 | EQUALIZER SWITCH | Place this switch in the IN position to activate the equalizer. |
| 7 | HIGH-PASS FILTER SWITCH | Place this switch in the ON position to cut off unnecessary low frequency. |
| 8 | LOW-PASS FILTER SWITCH | Place this switch in the ON position to cut off unnecessary high frequency. |
| 9 | EQUALIZER CONTROLS | Nine-band filters offering 12dB boost and cut at each center frequency. |
| 10 | POWER INDICATOR | Illuminates when power is switched on. |
| 11 | PEAK INDICATOR | Illuminates when the output signal reaches the rated output power level. |
| 12 | OUTPUT FUSE | Prevents excessive current flow. |
| 13 | AC FUSE | Prevents excessive current flow. |
| 14 | BLANK PANEL (USER'S SPACE) | A space (4" W x 2-3/8" H x 3-3/4" D) is provided for optional expanding kits or custom configurations. |
| 15 | EQUALIZER SECURITY COVER | Prevents inadvertent changes to equalizer control settings. |
| 16 | KEY-LOCKED DOOR | Secures the unit and prevents tampering. |
Rear Panel Connections
The rear panel provides connections for power, speakers, and input modules:
| Item | Name | Function/Description |
|---|---|---|
| 1 | AC POWER CORD | Connects to the power source. |
| 2 | SPEAKER OUTPUT TERMINALS | Connects to speakers. |
| 3 | OUTPUT TERMINALS | Select output impedance with this terminal. |
| 4 | LOW-CUT SWITCH | Cuts off unnecessary low frequency. |
| 5 | MODULE INPUT PORTS | Accepts plug-in modules, selection determined by application. |
| 6 | MUTE TERMINAL | When using modules with muting function, short-circuiting this terminal mutes input signals. |
| 7 | BRIDGING INPUT/OUTPUT | Used as a mixing bus or for recording output. Input impedance should be greater than 10k ohms. |
| 8 | CORD CLAMP | Secures lead wires from module inputs, mute terminals, and bridging input/output terminals. |
A block diagram illustrates the internal signal flow, including input stages, equalizer, compressor, muting, and output stages.
Installation and Connection
Installation requires optional back boxes: BX-9F for flush mounting in four-inch walls and BX-9S for surface mounting. The procedure involves attaching hinges to the back box, then securing the amplifier chassis to the hinges using screws. Power cables should be connected according to color coding and insulated. Speaker cables connect to the speaker terminals. Output impedance is selected via terminals on the front panel, supporting 4-ohm unbalanced, and 8-ohm, 25V, or 70V balanced connections using shorting bars.
Speaker Impedance Selection Diagrams:
For 4-ohm or 8-ohm connections:
- Insert shorting bar between 4Ω and OT IN for 8-ohm connection.
- For 4-ohm connection, no shorting bar is used on the 4Ω terminal.
For 25V or 70V line connections (BALANCED TRANSFORMER OUTPUT):
- Insert shorting bar between 4Ω and OT IN for 10.4-ohm (25V line) or 41-ohm (70V line) connections.
- For W-912A, the corresponding terminals are 5.2-ohm (25V line) or 41-ohm (70V line).
Operation
Power On: After connections are complete, turn the power switch ON. The power indicator illuminates, and the amplifier becomes operational after approximately 5 seconds.
Volume Adjustment: Adjust individual input and master volume controls for the desired output level. The peak indicator warns when the output signal is too high, indicating a need to reduce volume to prevent sound quality degradation.
Graphic Equalizer: The one-octave graphic equalizer (9 bands) adjusts frequency response to suit room acoustics, reduce feedback, and improve intelligibility. The EQ switch activates the equalizer; turning controls clockwise boosts frequencies, counter-clockwise cuts them. Placing the EQ switch in the OUT position bypasses the equalizer for a flat response.
Filters: The HIGH-PASS FILTER switch (ON position) cuts low frequencies (e.g., below 180 Hz at 12 dB/octave). The LOW-PASS FILTER switch (ON position) cuts high frequencies (e.g., above 7 KHz at 12 dB/octave). Placing filters in the OFF position bypasses them.
Compressor: The COMPRESSOR CONTROL switch bypasses the circuit when OFF. Turning it clockwise activates the compressor and adjusts the limiting level. Setting it too far clockwise may excessively limit output; adjust to a point that prevents the peak indicator from lighting.
Output Fuse: Each amplifier has an output fuse to protect against short circuits or overloading. If speakers are not producing sound, check the fuse and ensure speaker cables are not short-circuited and the load does not exceed ratings.
Heat Sink Protection: If the heat sink temperature exceeds 105°C, a protection circuit disconnects the output. Output resumes automatically as the temperature decreases. This may indicate overloading or excessive output operation.
Specifications
| Model | W-906A | W-912A |
|---|---|---|
| Type | Wall mounting 6-channel mixer power amplifier | |
| Output Power | 60W RMS | 120W RMS |
| Power Bandwidth | (D): 20-20,000Hz, 0.5% THD (T): 50-20,000Hz, 0.5% THD | (D): 30-20,000Hz ± 1dB (T): 30-15,000Hz ± 1dB (T): 30-20,000Hz +1dB, -3dB |
| Total Harmonic Distortion | 0.02% at 1 KHz, rated output | 0.02% at 1 KHz, rated output |
| Inputs | Six input ports: Each port accepts any input module except T-01S. Use T-01S only in port #5 or #6. One bridging input/output. | |
| Input Sensitivity/Impedance | Input ports #1 to #6: 100mV/10K ohms Bridging input/output: 100mV/3.3 K ohms | Input ports #1 to #6: 100mV/10K ohms Bridging input/output: 100mV/3.3 K ohms |
| Outputs | (T): 8 ohms, 25V & 70V, balanced (D): Less than 0.5dB, no load to full load. | (D): 4 ohms, unbalanced (T): Less than 1.0dB, no load to full load. |
| Output Regulation (1KHz) | Controls OFF: 90dB Master volume Max: 77dB | Equalizer IN: 88dB Compressor IN: 84dB |
| Signal to Noise Ratio (Band Pass: 20 - 20,000Hz) | - | - |
| Compression | Attack time: no greater than 2 milliseconds Release time: adjustable 20~2000 milliseconds | Compression range: 20dB Distortion: less than 1% |
| Equalization | 9-Band ISO One-octave graphic equalizer Center frequencies: 63, 125, 250, 500, 1000, 2000, 4000, 8000, 16000Hz Equalization range: ± 12dB | |
| Filters | High-pass filter: 180Hz 12dB/octave Low-pass filter: 7KHz 12dB/octave | |
| Controls | 6 Input gain controls, 1 Master gain control, 1 Compression level control, 9 Equalizer controls, 1 Power ON/OFF switch | |
| Indicators | 1 LED power indicator, 1 LED peak indicator | |
| Protection | Self-protection, with 2 AC fuses (1 inside) and 1 output fuse | |
| Connectors | Input #1 to #6: Card-edge connector Output: Screw-terminal strip Bridging input/output: Screw-terminal strip Mute: Screw-terminal strip | Input #1 to #6: Card-edge connector Output: Screw-terminal strip Bridging input/output: Screw-terminal strip Mute: Screw-terminal strip |
| Power Consumption | AC 120V, 60Hz, 100W | AC 120V, 60Hz, 180W |
| Dimensions in inches (mm) (hight) x (Width) x (Depth) | Face panel: 26-3/4" (680) x 16-1/4" (412) x 1-1/8" (28) BX-9F Back Box: 24-3/4" (628) x 14-1/4" (362) x 3-7/8" (98) BX-9S Back Box: 26-3/4" (680) x 16-1/4" (412) x 3-7/8" (98) | Face panel: 26-3/4" (680) x 16-1/4" (412) x 1-1/8" (28) BX-9F Back Box: 24-3/4" (628) x 14-1/4" (362) x 3-7/8" (98) BX-9S Back Box: 26-3/4" (680) x 16-1/4" (412) x 3-7/8" (98) |
| Weight (without input modules and back box) | 13.7Kg (30.1 lbs.) | 17.3Kg (38.1 lbs.) |
| Color | Silver | |
| Standard Accessories | 3 Volume control covers | |
| Other Features | Output disconnect for approx. 5 sec after power turned on. Muting Function: Accomplished by input module model X-11S, B-11S and E-11S. | |
Plug-in Modules and Accessories
A wide variety of plug-in modules are available to customize the functionality of the TOA W-900 series amplifiers. These modules connect via edge connectors on the front panel and include options for microphone preamplification, phono input, auxiliary input, bridging, line matching, paging, and tone generation. Each module type has specific input sensitivity, gain, and impedance characteristics, as well as connector types (e.g., XLR, Phone Jack, RCA, Screw Terminals).
Module Categories and Features:
- Microphone Preamplifiers (H-01, H-21, H-02, H-22, H-03): Offer low-impedance or high-impedance inputs, with controls for high-cut, low-cut, and gain. Some models (H-21, H-22) include remote volume control.
- Mag. Phono Preamplifiers (E-01, E-11): Provide RIAA equalization for phono inputs, with gain controls.
- Auxiliary Preamplifiers (X-01, X-11, X-21): For high-level sources, with gain controls and remote volume control options (X-21).
- Bridging Transformer (B-01, B-11): For high-impedance lines, with muting function (B-11).
- Line Matching Transformer (L-01): For matching 600-ohm lines.
- Paging Input (I-01, I-01C): Designed for TOA intercom systems, allowing paging signals to be integrated. Features adjustable mute delay for overriding background music.
- Line Output (T-01): An output module with a transformer, serving as a line output for recording or transmitting signals to external equipment.
- Tone Signal Generators (S-01, S-02, S-03): Generate 1kHz sine wave, yelp/buzzer, or chime signals for attention-getting or testing purposes.
Module Connection Diagrams:
Various connector types are supported, including:
- CANNON XLR: 3-pin (Female, Male) connectors for balanced and unbalanced connections.
- Phone Jack: 1/4" (6.3mm) jacks for unbalanced inputs.
- RCA Phono Jack: Standard RCA connectors for unbalanced inputs.
- Screw Terminals: For connecting potentiometers or other signal sources.
Block diagrams for each module type illustrate internal circuitry, including gain controls, electronic attenuators, filters (low-cut, high-cut), and muting functions.
Operation Notes for Specific Modules:
- Muting (E-11, X-11, B-11): Closing a switch connected to the MUTE TERMINAL attenuates input signals by approximately 60dB, giving priority to microphones during announcements.
- Remote Volume Control (H-21, H-22, X-21): Connecting a 10kΩ potentiometer to the designated terminal allows remote control of sound volume.
- T-01 Series: Used for transmitting mixing signals to external equipment or as a recording output. It operates approximately 5 seconds after power is supplied.
- S-01, S-02, S-03: Operated by closing remote switches to generate specific audio signals.
- I-01C (Paging): Paging is initiated by dialing a station number. The module can override background music during paging and has an adjustable mute delay.
