How to Connect a Tascam 70D to an iPhone for Facebook Live (or Other Reasons)

Say you want to do Facebook Live but have good audio, and happen to have a Tascam 70D audio recorder. It’s super easy to connect it to your iPhone. This should also work with other Tascam recorders that have 1/8″ Line Out/Camera Out jacks, though the setting might be named differently.
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Buy one of these adapters, plug into phone
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Connect the Tascam’s Line Out to the Microphone side of that adapter using a standard 1/8″ cable (this one is coiled and nice)
Be aware that, even though the TRRS adapter has a Headphone connector, I couldn’t get audio out while streaming to Facebook Live. But if you set it up as I did above, you can monitor on the Tascam and be (reasonably) confident it’s the same on FB. At least until Facebook randomly changes something on us.