I am trying to use my Shure sm7b as the microphone for my VOIP calls on my iphone. The app I use for VOIP calls is only available on iOS. I have an adapter to connect my Focusrite Solo audio interface directly to the iphone and this works. However, I lose the post processing filters that my PC provides via OBS. I also lose sound as the iphone cannot send audio out to a different device than what is connected via the lightning port or via bluetooth.
What I want to do is send my voice to my pc/OBS then use the PC's motherboard speaker jack (realtek) for my audio out. I then want to send the speaker signal to my iphone as mic audio in. I will split off the audio out of the iphone to some headphones with a Y splitter so I can hear the call.
I understand that speaker/line level/mic level are all different impedence. I know that I can solder my own resistors to create an attenuation adapter to bring line level signal down to mic level. This is beyond my skillset. I also know that a DI box can bring a line level signal down to a mic level and switch an unbalanced to balanced signal. I don't know if my pc speaker jack is line level or not. All my research says that all speaker signals are orders of magnitude higher than line and mic level.
I've seen a solution that may work by using a DI box in reverse. Unfortuantely, I don't have as nice of an interface than this poster. But their setup proves that an analog signal at the right impedence will trigger the iphone to accepting the signal as if a microphone is connected.
Can anyone tell me how I can convert a motherboard speaker audio out signal to a mic level signal? Is there any commercial attenuator that I can buy to achieve the correct voltage/olhms to trick the iphone into believing there is a mic attached?
My current hypothesis is:
Shure sm7b -> Focusrite Solo interface -> pc -> obs -> default speakers -> TRS male to TRS male cable -> trs to TRRS adapter -> port of y TRRS splitter -> lightning to TRRS dongle -> iphone (signal is probably too hot)
iphone audio out->lighting to TRRS dongle->TRRS y splitter-> headphones in one side of TRRS y splitter.
Best Answer
You need an attenuator - no way round that.
I didn't find the exact specific cable you need (& actual product recommendations are off-topic here), but I did find these guys - HeadsetBuddy - What is line level and how is it different from mic level? - who actually appear to give a damn about finding the right cable, based on impedance & level-matching.
Make sure you have the right info on your laptop output - I'd expect it to be TRRS usually, & probably but not infallibly CTIA. Apple devices are always CTIA, some others have yet to catch up & still use OMTP - CableChick - Understanding TRRS and Audio Jacks
…unless that's a dedicated speaker out - which might be hotter than a headset out; you'll have to check the computer spec. It might be the difference between needing 10dB, 20db or more attenuation.