1

I have an audio signal coming out from an iPhone which I would like to record in iPad using its mic input.

I have tried this with simple resistor divider (and TRS-TRRS connectors), but it seems to worsen the sound quality.

How can I do this without worsening the sound quality ? Are there any off the shelf components I could use to achieve this ?

I came across this adaptor, but it says 50dB loss, I guess my sound quality would drop, which is not great for my application.

Pravi
  • 297
  • 1
  • 7
  • 12
  • 3
    50dB loss refers to a decrease in signal amplitude .... it does not refer to signal distortion – jsotola Sep 27 '18 at 01:34
  • "but it seems to worsen the sound quality.", where is your proof to back that up? - "I guess my sound quality would drop", that's a non-logical assumption you've made, unless you... again, have proof, or no proof. – Harry Svensson Sep 27 '18 at 02:59

1 Answers1

3

You need to add an AC coupling capacitor before your signal goes into the iPad. I'm thinking that about 30dB attenuation should get you in the ballpark level-wise.

Also be careful of the TRRS pinout both coming out of the iPhone and going into the iPad. Check online sources for the pinout - my recollection is that Apple does things differently from anybody else.

schematic

simulate this circuit – Schematic created using CircuitLab

Dwayne Reid
  • 23,792
  • 2
  • 38
  • 70
  • "my recollection is that Apple does things differently from anybody else." - Sadly and annoyingly true. – Harry Svensson Sep 27 '18 at 02:26
  • Make sure you pick a CLEAN GROUND for the bottom connection to R2. – analogsystemsrf Sep 27 '18 at 04:01
  • 1
    Both ground connections come from the TRRS plugs used for the two devices. That's as clean as it gets. – Dwayne Reid Sep 27 '18 at 04:53
  • @Dwayne Reid, When I use a capacitor as shown in your circuit iPad doesn't detect the mic. I believe this is because iPad requires a DC signal for the mic to be recognised. – Pravi Sep 27 '18 at 11:20
  • That indeed could be the case. In that case, omit the capacitor but multiply the resistor values by 10. That should keep the bias current in the region that the iPad is happy with. – Dwayne Reid Sep 27 '18 at 16:23
  • 1
    Please let me know if that works for you and I'll modify my answer for the next person who is trying to do what you are doing. – Dwayne Reid Sep 27 '18 at 16:24
  • That configuration is position sensitive - you have to have the right ends at the connection. There are some other designs here. Impedance match. http://www.uneeda-audio.com/pads/ – Ernesto Ochoa Feb 06 '22 at 17:31