Ref Amp Front 2



Ultra Precision Measurment Amplifier


Ref Amp complete

- Precision 23W (4Ω) amplifier for all measurement purposes

- Selectable mains (115V or 230V)

- Ultra high bandwidth

- Ultra low distortion

- Ultra low noise

- Three different gain modes (0dB, 10dB and 20dB)

- Drives all kind of loads (2Ω stable)

- Optional current and voltage sense outputs for high precision impedance measurements




Physical Lab proudly introduces the Ultra Precision Measurement Amplifier. This beast is the best and most versatile measurement amplifier money can buy! The amplifier is suited for all kind of ultra-precise measurement demands. The response of the amplifier is flat (± 0,1dB) from DC to 100kHz! The extended bandwidth allows ultra-sonic measurements and makes it an ideal tool for measuring MEMS, headphones, microphones and microspeakers with high precision. Driving low or complex impedances are handled with ease. Three selectable gain modes (0dB, 10dB and 20dB) ensure the best range for your requirements.The amplifier can be equipped with an extra sensing board for precise current and voltage measurements. The board is providing several extra outputs:

- Direct amplifier output for the DUT

- Mini XLR current sense output

- Mini XLR voltage sense output


Beside of current or voltage measurements the outputs can be used for direct impedance measurements under constant voltage conditions. The output impedance of the mini XLR outputs is switchable. One can choose between direct amplifier output impedance (1Ω) and balanced line output impedance (100Ω). 

Rear view with the additional sensing board:


Ref Amp back2

  High-Res picture


Technical specs:


   0dB Mode  10dB Mode  20dB Mode
Gain  0.0dB 9.9dB   19.8dB
Sensitivity (Input)  9V 3V  1V 
SNR (DC - 20kHz , max Output) 125dB 125dB  122dB 
SNR (fullrange , max Output) 119dB 119dB 116dB
Noise (DC - 20kHz) 4.4uV 5.2uV 16.2uV
Noise (fullrange) 9.2uV 10.8uV 16.2uV
THD+N (1W at 1kHz , 4Ω) 0.0012% 0.0012% 0.0015% 
Dynamic Range AES17 124dB 123dB 121dB
Output Impedance 0.32Ω 0.32Ω 0.32Ω
CMRR (fullrange) >80dB >80dB >80dB
Deviation (20Hz - 20kHz)  < ± 0.01dB  < ± 0.01dB  < ± 0.01dB
Deviation (DC - 100kHz)  < ± 0.10dB  < ± 0.10dB  < ± 0.10dB
Max Output (THD+N <1% , 4Ω Load) 23W 23W 23W