The RigidEnhancer 1.1 is a portable, high-input-impedance voltage preamplifier designed for passive capacitive piezoelectric hydrophones and contact microphones. It amplifies the low-level voltage produced by the sensor, providing a stronger signal for connection to compatible audio recorders, audio interfaces, data-acquisition systems, oscilloscopes, amplifiers, and other measurement or recording equipment.
The RE1.1 is an updated version of the RigidEnhancer 1.0, developed to provide accurate selectable gain, convenient battery operation, and improved performance with high-impedance recording and measurement equipment.
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Selectable gain
The preamplifier provides five manually selectable voltage-gain settings:
- 5 dB
- 15 dB
- 25 dB
- 35 dB
- 45 dB
The external five-position control makes it easy to match the gain to the signal level and application.
Lower gain settings provide greater high-frequency bandwidth and are recommended for stronger signals and wideband ultrasonic work. Higher gain settings are useful for weak audio-frequency and lower-ultrasonic signals, provided that the input level is kept low enough to avoid clipping.
Hydrophone compatibility
The RE1.1 is intended for passive capacitive piezoelectric hydrophones. Its recommended source-capacitance range is 10 nF to 30 nF, with a 20 nF source used during testing.
Because this is a voltage preamplifier, its effective charge-to-voltage sensitivity depends on both the selected gain and the capacitance of the connected hydrophone.
The BNC female input allows a compatible hydrophone to be connected directly to the preamplifier. The 3.5 mm output can be connected to compatible recording or measurement equipment using an appropriate audio cable.
For the best gain accuracy, output headroom, and battery life, connect the output to equipment with an input impedance of at least 10 kΩ. A higher input impedance is preferable when available.
Frequency response and output capability
With the 50 Hz notch network excluded from the measured signal path, the direct-voltage response did not reach a low-frequency −3 dB point down to 1 Hz.
High-frequency bandwidth depends on the selected gain. Preliminary measurements found:
- More than 400 kHz bandwidth at 5 dB gain
- Approximately 139 kHz bandwidth at 25 dB gain
- Approximately 18 kHz bandwidth at 45 dB gain
The lower gain settings are therefore better suited to wideband or ultrasonic applications. The 45 dB setting is better suited to weak signals within the audio and lower-ultrasonic ranges.
Portable enclosure and controls
The preamplifier is housed in a durable 3D-printed enclosure designed for portable and long-term use. Its accessible controls and replaceable batteries make it suitable for field measurements, underwater listening, acoustic experiments, equipment testing, and portable recording setups.
Important operating notes
- Use a recorder or measurement input with an impedance of at least 10 kΩ.
- Use lower gain settings when greater high-frequency bandwidth is required.
- At higher gain settings, reduce the hydrophone signal level if clipping occurs.
- Replace the batteries if the output becomes unstable or the available output level decreases.
- For extended unattended recordings, consider an external higher-capacity power option.
- If mains-frequency interference is present, software filtering may be used during recording or post-processing.
