I found the apple connector has the microphone signal on the sleeve ring and second ring. That explain why it does not work out of the box.
I can't find any adapter on the market for that. However it seems relatively easy to:
- cut the wire before the existing connector
- install a TS 1/8 mono male connector on the microphone end
- install a TS 1/8 mono female connector on the existing connector end
that way, I will still be able to use the iRig mic on a iPhone by using the existing connector, and also plug the microphone on any 1/8 mono input by using the TS 1/8 mono male connector I installed.
[MIC]----------cut-here------[iRig TRRS 1/8 Connector]
[MIC]---------[TS 1/8 Male] <----> [TS 1/8 Female]----[iRig TRRS 1/8 Connector]