It might help if you gave the make and model of the equipment involved in your question... Someone might RTFMs and give an answer... Or give other alternatives...
Have you tried Bluetooth wireless streaming from your iPhone to the Teac AI101-DA DAC integrated amplifier... Might be a little easier to use than wired USB... There is no analogue out on the newer iPhones... They are all Bluetooth wireless now for earbuds and external speakers...
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