．Power by external +48V phantom power ．Built-in UNiKA-PROTM EI30A10E isolation transformer ．Use British OEP PT-4 1:1 audio pulse transformer in phantom power circuit ．+48V status indicator on the upper cover ．The input socket uses Combo jack ．Use TRS jack as through out terminal ．At 0dB input, the set load impedance is 260KΩ, which can clearly show the high frequency overtones, harmonic and graininess of electric guitars or electric bass ．50Ω ultra-low impedance output, suitable for various types of mixers and pre-amp equipment ．There is 0dB/-20dB input signal attenuation switch with status indicator ．The output is equipped with a GND/LIFT switch PRO 148 is an active single-channel DI box. Unlike traditional DI, PRO 148 uses +48V phantom power instead of the traditional 9V dry cell battery, so users can use it on the mixer or external phantom power supply. Power is supplied to PRO 148, the power supply circuit and the output signal line are shared, and no additional power cord is required. The +48V indicator is set on the upper cover. The +48V circuit specially selects the British OEP PT-4 pulse transformer. PRO 148 has a built-in UNiKA-PROTM EI30A10E 1+1:1+1 isolation transformer, which has a special copper foil layer and a dedicated ground layer, which allows this device to restore high signal/noise ratio and dynamic sound, and can avoid unnecessary leakage caused by radio frequency interference, ground interference and potential difference. PRO 148 is especially suitable for electronic musical instruments, recording studios and fixed installation projects by using mixers. The PRO 148 uses a balanced/unbalanced combo socket on the input, and a TRS through out is convenient for musician to pass the direct signal to the instrument amplifier. In addition, it is equipped with a 0/-20dB attenuation switch and LED indicator, which is suitable for various types of audio signals with high and low impedance. The output terminal is also equipped with a GND/LIFT button to quickly eliminate ground noise. INPUT PAD ATTENUATION The most widely used DI box is to connect electronic musical instruments, sound source of A/V equipment and computers, convert their output signals into balanced signals and then extend the transmission distance. The most ideal state is to set the attenuator to 0dB position (button up) for musical instrument. For some other type of signals, you can press the button to make the signal is attenuated by 20dB to avoid clipping caused by signal overload. When the button is pressed, the PAD indicator on the right will light up. POWER SUPPLY PRO 148 is an active DI box and requires +48V phantom power. It can work normally when it is powered, but no additional power supply is required. Just use balanced wires to connect the device to the mixer’s input channel, and turn on the +48V power switch of the mixer, similar to connect a condenser microphone to the mixer. When the +48V power supply is suppling properly, the +48V ACTIVE indicator light on the upper cover will light up. WARNING: Before connecting the device, do not turn on the +48V switch of the mixer. ELIMINATING GROUND LOOP NOISE The built-in channel independent balanced isolation transformer has solved the potential difference leakage problem. When the system causes a ground loop due to poor wiring, the noise can be eliminated through the GND/LIFT button. The GND/LIFT button determines whether pin 1 of the output XLR is grounded, grounded when it bounces, and disconnected from ground when pressed.