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PA-4 Hydrophone Preamplifier

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For P48-powered applications, please consider the newer, smaller and lower-cost PA6 hydrophone preamp.

Low-noise broadband hydrophone amplifier for use with AS-1 and others. Provides the necessary signal conditioning for connecting hydrophone to recorder, sound interface, or test equipment. Jumper-selectable gain from 6dB to 56dB. Balanced differential output, can be phantom powered or used with external 6 to 12-volt DC power supply. Custom configurations of gain and input impedance and power supply are available by special order.

Available fully assembled as P48 version for use with microphone preamps that offer phantom power or DC version for external power. Also sold as board only.


Options Detail:

P48: For use with microphone preamps offering standard IEC P48 phantom power. Typically works with reduced headroom with phantom power voltages as low as 24 volts. NOTE: It is possible using this order page to select other output options for this P48 option. The P48 configuration should only ordered with XLR male or 1/4" TRS output for use with standard microphone preamps.

DC: For use with with external 6 to 12-volt DC power (Caution: do not exceed 15VDC). Options for connections to any standard audio or test device. Supplied with 9V PP3 battery connector, but designed for compatibility with low-cost voltage adapters and rechargeable battery packs made for closed-circuit video systems. This allows the user to buy lithium battery packs without the limitations of air shipping and with capacity to meet your requirements. Power adapters can also be purchased locally for correct voltage and wall plug types. Please note that stable, low-noise regulated power supplies are necessary for best noise rejection.

For connection to mobile phones, tablets and newer computers with headset jacks, order the DC configuration with 3.5mm TRS (single-ended mic) output and use this Y-adapter. This will allow you to monitor the signal with headphones or speakers while recording. Requires software support. Hardware limitations may apply.

For connection to stereo systems with dual RCA input jacks, order the DC configuration with 3.5mm TRS (line) output and use this Y-adapter.

Default setups: Leave instructions on order form if you have special requirements; we are happy to deliver amp configured exactly according to your needs. See user manual for setup details.

P48 options: balanced output, 26dB gain
DC power, XLR or 1/4" TRS output: balanced output, 26dB gain
DC power, 3.5mm TRS output, SE mic: non-inverting, 20dB gain, wired for stereo output (tip and ring common, sleeve to ground)
DC power, 3.5mm TRS output, Line: inverting, 50dB gain, wired for stereo output (tip and ring common, sleeve to ground)
DC power, BNC output: non-inverting, 20dB gain (consider the source level of your acoustic signals, as well as your bandwidth requirements and the full-scale input voltage of your measurement equipment and provide specific instructions if needed.)

BO: Sold as board only. Screw terminal connections. See user manual for additional detail. NOTE 1: Due to limitations with options processing in this form, your order will list one of the output options that are available for the DC configuration (XLR by default). This is not applicable to the BO configuration; no connectors are shipped. NOTE 2: This product is guaranteed to be delivered in working condition. No warranty period applies. Please see "Special Limitations" within our General Warranty Statement for additional detail. CAUTION: The PA4 board has no protection for overvoltage on the DC power input terminal. Do not exceed 15VDC. See user manual and ensure all connections are within specification.

Use Group: Determines input impedance. This is not user adjustable. Default is 2.2 Mohms. When used with Aquarian Audio hydrophones, such as the H1a, H1c or H3, input impedance is set at 300 Kohm to better match the higher-capacitance sensors. This helps to block infrasound and will make the amp more stable with acceleration and pyroelectric noise.

See User Manual for additional product details and specifications.


Default board setup: 26dB gain, differential (balanced) output, P48 phantom-powered


Input Referred Noise:

< 1µV

10nF input shunt

Unweighted 20Hz - 20KHz

-3dB Bandwidth:

14Hz - 3MHz

14Hz – 280KHz

14Hz - 48KHz

12dB gain

26dB gain 2KΩ output load

50dB gain




Max output:


@1KHz, 2KΩ load, 10% THD

Max input:

>1.25V RMS

Note <1>

Current consumption:

6.5 mA

Note <2>

Z in:


Note <3>

Z out:


Each phase to ground





23mm x 40.6mm, max height 16.3mm, 12g.

Enclosure: 25mm x 25mm x 68mm (100mm inclusive of BNC connector and cable gland) balanced output cable: 150mm long. 90g.

<1> Specified for minimum gain. Limited by Max output minus gain. Input is diode protected against overload and voltage transients. Approximately 210dB SPL re: 1 µPa, or 31.5KPa when used with Aquarian Scientific AS-1 hydrophone.

<2> Input shorted, 2KΩ output load. Rated for IEC P48 phantom power (default configuration). < 3.5mA with typical 24V phantom power or external DC power (J3 open).

<3> Can be modified by changing R4. When used with the Aquarian Audio H1 or H3 hydrophones, the user will benefit from lowering Z in to avoid infrasonic acceleration or pyroelectric noise that can saturate the amp.

This amplifier can be modified for additional bandwidth, gain, or power requirements. Alternate connectors may also be accommodated.

Contact Aquarian Scientific for custom configuration or additional technical support.