Coming back to this, I'm finding that building the cable is not so simple. I had thought that if I just drop line-level down to the same voltage as standard electret microphone, everyone would be happy. Boy, was I wrong!
It turns out my collection of Android cell phones wanted 40dB attenuation. But apparently, all indications are that iOS wants only 20dB.
Things got even stranger when I tested my laptop and found it wanted -10dB on it's TRS input. And digging into the microphone settings, that was with 10dB boost! Turn off all boost, and it's happy with full line level input.
So, using CalS201 excellent ASCII art as a starting point, here is my suggestions with the values for different levels of attenuation.
Code: Select all
RECORD DIY 3.5mm to Device
OUT JACK ATTENTUATOR
316mv-)|(---< [T]RS <-----[R1]-------------> TRR[S] or [T]RS
600 )|( [R2]
ohm )|( |
-----)|(---< TR[S] <----------------------> TR[R]S or TR[S]
For TRRS (headset) Connection:
-20dB 12K 1.2K
-30dB 39K 1.2K
-40dB 120K 1.2K
For TRS (mic in) Connection:
-10dB 10K 4.7K
-20dB 47K 4.7K
I'm in the middle of designing a cable that will work with either TRS or TRRS and will have 3 levels of attention to choose from. That way, I should be able to deal with most anything.
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