DaytonAudio SA70 - User Manual

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Summary

Input and Output Connections

Low-Level Inputs

RCA jacks for standard line level stereo inputs, combined internally to mono.

High-Level Inputs

Speaker level inputs using spring clip jacks for bare wire connection.

High-Level Outputs

Speaker level passthrough outputs for connecting to main speakers.

Power Input

Hardwired AC power cable and externally-accessible fuse for 120 VAC, 60 Hz.

Controls and Indicators

Gain Knob

Adjusts amplifier input sensitivity to match the pre-amp source for optimal level.

Frequency Knob

Sets the highest frequency for subwoofer reproduction (60-180 Hz).

Power Switch and LED

Controls power modes (On, Off, Auto) and indicates operational status.

Subwoofer Driver Output

Connects amplifier output to the subwoofer driver with color-coded wires.

Important Safety Instructions

Electrical Safety

Precautions against electric shock, including not removing covers or exposing to moisture.

Ventilation and Placement

Ensures proper airflow and placement away from heat sources and potential cord damage.

The Dayton Audio SA70 Subwoofer Plate Amplifier is a robust and versatile audio component designed to enhance the low-frequency performance of home stereo, home theater, and multimedia audio systems. This amplifier is engineered to deliver high-quality sound reproduction, providing years of reliable operation for compact subwoofers.

Function Description

The primary function of the SA70 is to power a subwoofer driver, integrating it seamlessly into an existing audio setup. It takes audio signals from various sources, amplifies them, and outputs the amplified signal to the subwoofer, thereby extending the system's bass response. The amplifier is designed to handle both line-level and speaker-level inputs, offering flexibility in connection to almost any audio system. It features a built-in low-pass crossover, which is crucial for ensuring a smooth and clean transition between the subwoofer's output and the main speakers' frequency response. This prevents the subwoofer from reproducing frequencies that should be handled by the main speakers, resulting in a more coherent and balanced soundstage.

A key feature of the SA70 is its comprehensive internal protection circuitry. This includes safeguards against common issues such as shorted speaker loads, thermal faults, and overload conditions. These protection mechanisms ensure the longevity and reliability of the amplifier, preventing damage to both the amplifier itself and the connected subwoofer driver. The amplifier also incorporates an auto-on/off circuit, which is activated by the presence or absence of an input signal. This intelligent power management feature conserves energy by automatically placing the amplifier in standby mode when no audio signal is detected for a period, and then powering it on instantly when a signal is present.

The SA70 utilizes a robust TDA7294 IC-based Class AB topology, which is known for its efficiency and sound quality. This design choice contributes to the amplifier's ability to deliver powerful and clear bass without excessive heat generation.

Usage Features

The SA70 offers a variety of input and output options, making it adaptable to different system configurations.

Low-Level Inputs (Left/Right): These are RCA-style jacks designed to accept standard line-level inputs from pre-amp level sources, such as a receiver's subwoofer output or a dedicated preamplifier. The amplifier internally combines stereo signals into mono, ensuring that the subwoofer receives a unified low-frequency signal. For optimal performance, both left and right input jacks should be connected to the source to drive the amplifier to its full output potential.
High-Level Inputs: These spring clip type jacks allow for connection with bare wire from the speaker-level output of a full-range amplifier. This is particularly useful when a dedicated subwoofer output is not available on the main amplifier. The SA70 derives a mono signal from the stereo input, which then feeds its internal crossover.
High-Level Outputs: Also featuring spring clip type jacks, these outputs allow the user to pass the full-range signal from the source amplifier through the subwoofer amplifier to the main left/right speakers. It's important to note that the signal to the main speakers is not filtered by the SA70's crossover; the impedance seen by the full-range source amplifier will only be that of the connected speakers. This feature is only active if the high-level inputs are being used.
Power Input: The unit includes a hardwired AC power cable and an externally accessible fuse. It is designed for 120 VAC, 60 Hz operation and is not suitable for 230V applications.

The amplifier's front panel (when mounted) features several controls and indicators for user adjustment and monitoring:

Gain Knob ("Gain"): This control adjusts the amplifier's input sensitivity to match the output level of the pre-amp source. Users can fine-tune this knob to achieve the best balance between low noise, linear level control, and sufficient output to drive the subwoofer effectively. It essentially acts as the "volume control" for the subwoofer system.
Frequency Knob ("Freq"): This control sets the highest frequency the subwoofer will reproduce, with a range typically between 60 Hz and 180 Hz and a 24 dB per octave slope. For music systems with main speakers capable of good bass, a lower setting (e.g., 60-100 Hz) might be appropriate. For smaller main speakers with limited bass output, a higher setting may be preferred. Experimentation is encouraged to find the optimal "overlap" for seamless integration with the main speakers and the room acoustics. When using an LFE (Low Frequency Effects) output from a home theater receiver, the frequency control should be set to maximum (180 Hz) to bypass the SA70's internal low-pass filter, allowing the receiver to manage the crossover frequency.
Power Switch (On, Off, Auto): This switch controls the amplifier's power state. In the "On" position, the amplifier is continuously active. In the "Auto" position, the amplifier enters a standby mode and will automatically power on when an input signal of approximately 10 millivolts or greater is detected. If no input signal is detected for 10-15 minutes, the amplifier will return to standby mode, conserving power.
Power LED: This indicator provides visual feedback on the amplifier's status. It illuminates green when the amplifier is in "On" mode or when an input signal is detected in "Auto" mode. If the protection circuit detects a short circuit or thermal overload, the LED will turn red, indicating a fault condition and that the unit has shut down for safety.
Output Lead for Subwoofer Driver: A rear-mounted, color-coded output lead (approximately 12" long) connects the amplifier to the subwoofer driver. The red wire (positive) uses an insulated .250" quick disconnect, and the black wire (negative) uses an insulated .205" quick disconnect. These connectors can be removed if the driver requires a different size or type, but proper polarity must be observed during connection (red = positive, black = negative).

Maintenance Features

The SA70 is designed for high reliability and minimal user maintenance. However, some aspects are important for its long-term performance and safety:

Fuse Replacement: The unit features an externally accessible fuse. In the event of a fuse blow, it should be replaced with a 1.6A, 250V fuse as marked. This is a user-serviceable part, but it's crucial to use the correct fuse type to prevent fire risk.
Ventilation: The amplifier should be operated in a well-ventilated area, with a minimum clearance of 2 inches from ventilation openings. This prevents overheating, which can trigger the thermal protection circuit and potentially shorten the amplifier's lifespan. It should not be installed near heat sources such as radiators, heat registers, stoves, or other heat-producing apparatus.
Cleaning: The unit should be cleaned only with a dry cloth. Avoid using liquids or abrasive cleaners.
Power Cord Protection: The power cord should be protected from being walked on or pinched, especially at the plugs, convenience receptacles, and where it exits the unit.
Electrical Safety: To reduce the risk of electric shock, the cover (or back) should not be removed, as there are no user-serviceable parts inside beyond the fuse. Servicing should be referred to qualified service personnel. The unit must be connected to an earth-grounded AC electrical socket. The safety purpose of the polarized or grounding plug should not be defeated. If the plug does not fit the outlet, an electrician should be consulted for replacement of the obsolete outlet.
Protection from Elements: To reduce the risk of fire and shock, the unit should not be exposed to rain or moisture. It should also be unplugged during lightning storms or when unused for long periods.
Hum Reduction: While designed to minimize hum, in rare cases, hum may occur due to grounding issues or cable TV systems. Troubleshooting steps include ensuring all audio components are connected to the same electrical outlet or circuit branch, disconnecting coaxial feeds from cable TV systems (and installing a coaxial line isolator if this resolves the issue), or using a line-level audio isolator/transformer connected to the subwoofer amplifier's line-in.
Not Suitable for In-Wall Mounting: The amplifier is explicitly marked as "NOT SUITABLE FOR IN-WALL MOUNTING," indicating that it requires external ventilation and should not be enclosed within a wall cavity.