Edited by FiiO-Shadow at 2015-2-3 18:23
We'd like to introduce some relative knowledge in plain English, since not everyone well knows about the electronics.
A. What does LO mean?
LO is for LINE OUT, terminologically called audio line output. It usually refers to the analog signal comes out from the audio sources.
Generally, signal come out from LO as standard music signal is used for follow-up audio processing such as amplification, sound effects, or adjusting the sound field.
See, signal from LO is mainly used for the proper transmission between different devices.
Thus,there is standard requirement of LINE OUT signal (mainly refers to the range ofsignal) within the range of international/national standard. For the most efficiently signal transmission, the input impedance of devices connecting with LO should be higher than 1000 Ω.
So, thekey feature of LO can simple summed as 1. Constant high level signal! 2. Suitable for devices with high input impedance.
B. What does PO mean?
PO is for power output.
The only one function of PO is to drive devices (such as headphones, earphones, and loudspeakers) converting the electrical signal into sound signal. It can be considered as the last step of the audio system that provide music signal and make it big enough for us to hear.
PO has no so much standard requirement as the LO. Generally, due to the demand of size and battery life of modern portable audio sources, now the headphones and earphones are usually designed to be with low impedance and high sensitivity. As a result, most of the portable music devicesare designed for headphones/earphones that with impedance of 16 Ω ~ 32 Ω, and sensitivity above 105 dB/mW. Meanwhile, it will just need output power of several milliwatts.
C. The main differences between LO and PO.
By the above brief introduction, we can know the two main differences between LO and PO.
1. LO is mainly used for high load impedance while the PO used for low one. 2. LO outputs voltage signal, and it requires for signal with enough range; PO outputs power signal, and it requires the product of voltage and current of the output signal should be higher than certain requirements.
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