G.R.A.S. 12AX 4-Channel CCP Power Module with Gain

Connection: CCP
Channels: 4
0, 20, 40 dB gain


The G.R.A.S. 12AX is a constant current power module for powering 4 CCP preamplifiers/microphone sets.

It is optimized for integration into a production environment. The anodized enclosure is sturdy and offers good protection against dirt, dust and moisture.

Except for the power switch, it has no external user controls. In this way unintended change of the gain settings is avoided.


As the 12AX is a 4-channel unit, it has 8 BNC connectors, 4 for the input from the microphones and 4 for the output to the analyzer. All connectors are mounted on the rear panel.

It provides 5 mA of constant current at +28 VDC compliance voltage level.

The gain is selectable individually for each channel by means of jumpers. These are accessible by removing a cover at the top plate. The gain can be set to 0, 20 or 40 dB. The chosen gain is indicated by green LEDs on the front panel. 

It has error detection at the input and overload detection at the output. The error detection at the input warns against a DC error, typically a short or a broken connection. The overload detection is applied at the output. If the signal exceeds 22 VACp-p, the overload detection will warn about it. DC error and overload are indicated by red LEDs on the front panel, one for each channel.

It has a low noise floor and a wide frequency range: At 0 dB gain, the noise is 1.5 µV and the frequency range from 1 to 300 kHz (+1/-3 dB).

It can handle long cables without significant degradation of the frequency performance.

It operates from 9 - 18 VDC from a mains voltage adapter which is included.


All G.R.A.S. products are made of high-quality materials that will ensure life-long stability and robustness. The 12AX is delivered with a 2-year warranty. The warranty does not cover products that are damaged due to negligent use.

Service and Repairs

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.

Frequency response (+1,-3 dB) @ Gain = 0 dB Hz 1 to 300 k
Frequency response (+1,-3 dB) @ Gain = 20 dB Hz 1 to 200 k
Frequency response (+1,-3 dB) @ Gain = 40 dB Hz 1 to 70 k
Output channel(s) 4
Output impedance Ω 75
Inherent noise (20 to 20 kHz) @ Gain = 0 dB µVrms 1.5
Inherent noise (20 to 20 kHz) @ Gain = 20 dB µVrms 15
Inherent noise (20 to 20 kHz) @ Gain = 40 dB µVrms 150
Gain settings, 20 dB steps dB 0, 20 and 40
Gain error dB ± 0.15 dB
Linear mode Yes
Type Constant Current Power (CCP)
Input channel, CCP 4
CCP preamplifier supply @ +28 V mA 5
Overload indication Yes
Power supply, external Vdc 9 to18
Weight g / oz 1100 / 38.8
G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.

All dimensions in mm.

Included items

Mains/line power supply

Optional items


Rack Mounting Kit (for mounting 2 x 12AX side by side)

G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.