I was on another audio recording job earlier this month, where I was miking up the various presenters with lapel microphones – compact lavaliers. Looking at the brief for the job beforehand, it looked as though I was going to be one audio channel short for my single bag setup, and was faced with the prospect of having to haul in a rack containing a mixing desk and 24 track hard disk recorder.

This was troublesome on several levels. Taking back ache out of the equation, the rack setup requires mains power, has to be positioned out of the way, and needs cables to be run across the floor. In addition, it’s very difficult to remain unobtrusive with all that kit, and I’d have needed to fill in a complex risk assessment sheet. All I needed was one extra channel – not even an important channel, because that presenter was only there to field the occasional question.

Then I thought about the iPhone solution I talked about in last month’s post. Why not us that as the fifth channel, with a lavalier mic plugged in direct?

There are a couple of iPhone lavaliers available out there, ranging from the Rode SmartLav at about £39 to something like the Audio Technica AT831-IPHONE at around $100 plus shipping. The AT831 appealed, but I didn’t have the time to wait for it to arrive. Generally I like Rode products, but in all the audio samples I’ve heard for the SmartLav there’s quite a lot of hiss.

But do you remember all those months ago when I suggested that the Audio Technica ATR-3350 lavalier could help you improve your videos immensely? I think it was January 2013. Well I have the previous model, the ATR-35S. I’ve not used it for quite some time, yet I always carry it around as an emergency back-up in case something vital fails. With it’s own power supply from a tiny 1.5V button battery, it can plug in just about anywhere.

So would it work with the iPhone? It didn’t work with my dynamic microphone adapter, but then its output impedance in the order of 1MΩ probably presented the iPhone with too high a resistance for it to accept than an external microphone had been connected. I suspect that the ATR-35S was also blocking the DC from the phone.

The solution was a new adapter, very similar to last month’s design, but this time with a 2k6Ω resistor in parallel with the ATR-35S across the iPhone connector’s ring and sleeve pins. Again, it worked perfectly and the sound quality was remarkably good.