Amplifier to the ear with the following three cases, one of the sources used, such as CD / DVD player not on the dedicated sennheiser mx680 sale output jack, then you can with a headphone amplifier, from the CD / DVD player's audio line output (LINE OUT) signal cable to the amplifier with two audio input jacks. Second case, the low sensitivity and high impedance headphones, such as with the existing audio player could not move, then have to buy headphone amplifier. The third situation is the high-end headphones, the sennheiser hd25 sale jack with the introduction of such existing headphones can not play the potential to add a headphone amplifier can further enhance the sound quality, in which case, we should consider the purchase a high quality headphone amplifier has.
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