What is the difference between “passive” and “active”?

Passive simply means that no external power is required to operate the device. Our passive adapters use shielded transformers to convert the balanced input signals from XLR connected mics to an unbalanced output for connection to the camera. The beauty about passive circuitry is that it is completely noise free for pure, clean sound. However, it does not provide any amplification so it requires that the source signal be sufficiently strong enough to drive the recording device adequately. Active means there is powered circuitry to provide amplification or other processing to the source signal. This of course requires power to operate. The advantage of using active circuitry is the clean amplification it can provide to replace the noisy amplification in the camera for an improved signal to noise ratio.