G.R.A.S. 14AA Electrostatic Actuator Amplifier

Freq range: 1 Hz to 200 kHz
IEC: 61094-6

Typical Applications and Use

  • Microphone measurements
  • Driving microphone sound sources
  • Electrostatic-actuator calibrations
  • IEC 61094-6 Compliance


The input to the 14AA is via a standard BNC socket on the front panel and any input signal up to 3 V peak-to-peak can be applied. This is then amplified by 40 dB to produce an AC output signal of up to 300 V peak-to-peak maximum. This AC output signal is also made available superimposed on + 200 V DC and + 800 V DC. This amounts to three parallel signal outputs available via sockets on the front panel marked as follows:

  • AC Output (BNC socket)
  • AC Output + 200 V DC (BNC socket)
  • AC Output + 800 V DC (banana socket) 

Driving microphone sound sources

With the AC Output superimposed on + 200 V DC and used as a modulated polarization voltage on a standard measurement microphone such as the G.R.A.S. 40BP, the microphone becomes a precison soundsource for generating high frequency acoustic signals. Alternatively, the AC Output alone can be similarly used with a prepolarized microphone such as the G.R.A.S. 40AD.

Electrostatic actuator calibrations

With the AC Output superimposed on + 800 V DC, it can be used as a modulated polarization voltage for electrostatic actuators, e.g. the G.R.A.S. RA0014 or RA0015, for measuring the pressure frequency response of condenser microphones.

The data sheet shows an example of a set up using this technique for accurately measuring the pressure frequency response of a condenser microphone in the range 100 Hz to 200 kHz.

Care should be taken when calibrating below 200 Hz because of the influence of pressure equalisation in the rear volume of the microphone.


All G.R.A.S. products are made of high-quality materials that will ensure life-long stability and robustness. The 14AA is delivered with a 2-year warranty. Damaged diaphragms in microphones can be replaced. The warranty does not cover products that are damaged due to negligent use, an incorrect power supply, or an incorrect connection to the equipment.


All repairs are made at G.R.A.S. International Support Center located in Denmark. Our Support Center is equipped with the newest test equipment and staffed with dedicated and highly skilled engineers. Upon request, we make cost estimates based on fixed repair categories. If a product covered by warranty is sent for service, it is repaired free of charge, unless the damage is the result of negligent use or other violations of the warranty. All repairs are delivered with a service report.

Frequency range (±2 dB) Hz 1 to 200 k
Power supply, external Vdc 110 to 240
Input signal, max. Vrms 1
AC output Vrms 100
Actuator output Vdc 800
Microphone polarization output Vdc 200
AC output impedance 1
Actuator output impedance 10
Microphone polarization output impedance 5.6
Gain dB 40
IEC standard 61094-6
CE/RoHS compliant/WEEE registered Yes/Yes/Yes
Weight g / oz 1400 / 49.42

Typical frequency response for the AC outputs, O VDC and +200 VDC

Optional accessories

G.R.A.S. RA0014 1⁄2” Electrostatic Actuator
G.R.A.S. RA0015 1” Electrostatic Actuator
G.R.A.S. RA0067 1⁄2” Microphone Output Adapter
G.R.A.S. AA0039-CL Customized Length BNC - BNC Cable