The output of the QY doesn't have any kind of carrier; it's just pure audio. It's meant to drive headphones, so its impedance is low (something under 100 ohms). This is lower impedance than a low impedance mic (600 ohms). But unlike a mic, the QY output is quite strong - as was pointed out, about 250mV, which is very much stronger than a mic. Unfortunately, it's not quite normal line level, which is 1000mV. See the connector materials may be sub par and more prone to dirt and corrosion, which causes crackles in the sound.
Hope I haven't anaesthetized or offended anynone.
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Yamaha Qy-70 uses