I tried an iPhone headset, not that great. Had best results so far (shown in the video I uploaded) with the use of the internal mic and my normal in ear Sennheiser earphones. Whatever you use has to be a line level input so if you want to use a dynamic mic you’ll have to run it through a preamp first. Remeber OP-1 Field supports some USB audio devices, so consider using your Zoom H4 since you have it but plug your dynamic mic into it instead.