Getting signals into and out of the iPhone and iPod touch

benfaber

Additional audio input/output information, for iPhone and iPod touch devices, is now available here.

xpressive-works

If i understand things right, some additional hardware is needed to get an audio-signal into iPod touch via the dock. Is there (or will there be) any possibility (e.g. some driver) to route the audio-signals to the USB-Connector cable?

benfaber

Is there (or will there be) any possibility (e.g. some driver) to route the audio-signals to the USB-Connector cable?

What exactly do you mean? Where would the signals go once they reached the USB cable?

In other words, what are you hoping to accomplish?

Kent

Ok, I'm confused.  Using a iPhone 3gs I want to send signal generator out and use the built-in mic with the octave analyzer simultaneously.  If I use a standard doc output or the earphone output, the signal is routed directly back in to the corresponding input.  To equalize speaker system, I need to be able to output pink noise while using the analyzers simultaneously.  Is this possilble?  Maybe with the Alesis ProTrack?  Thanks in advance!

benfaber

Kent,

If you plug a stereo cable into the headset jack, the selected output will be headphones and the selected input will be the built-in microphone. The headset input won't be selected unless you connect a suitable load to the input channel of the headset jack (which requires a four-conductor mini-plug).

However, based on some measurements I made on June 19 (see the blog), I don't recommend using anything other than the dock input (line input) of the iPhone 3G S for frequency response measurements (unless you don't care about frequencies below 200 Hz).

You could use the Alesis ProTrack or the Tunewear Stereo Sound Recorder for line-in, but you would still need to use the headset/headphone jack for output. (http://blog.faberacoustical.com/2009/iphone/dock-connector-audio-io/)

The new demo video shows SignalScope Pro making frequency response measurements on a 2G iPod touch (you can see the low frequency roll-off, which is due to the iPod touch headset I/O).

Ben

Kent

Ben,  thanks for your response.  At first I could not reconcile your first paragraph as the application would not select mic input with signal generator going out the headset jack.  However, I tried sliding the stereo (tip/ring/sleeve) connector out a fraction of an inch and behold, the expected behavior manifested itself.  Just what I needed.  Must be something shorting if the connector is not seated exactly right.  Thanks again.  Kent

gadzby

I would like to use SSP for equalizing my car audio system.  My iPhone (original) connects to the car system using a dock connector -  I have no aux jack input.  Ideally I would use SSP to generate pink noise to the dock output while simultaneously capturing input from the Apple headset microphone (original version), or another mic attached to the headset jack.

I performed a simple experiment to see if this might be possible.  I first setup my iPhone to produce music  on the Apple headset, then connected the car's dock connector.  At that point the desired result was achieved, i.e., the music switched from playing on the headset to the car's stereo system.  But I am unable to determine if the Apple headset micrphone could be tapped by SSP in this configuration.  Would this work, or would the iPhone input also be switched to the dock?

Of course the other option would be to play a CD containing pink noise from my CD player while capturing input using the headset mic.

Grant

benfaber

Grant,

The iPhone will prevent you from using the headset input and the dock output at the same time. However, if your goal is to use the 1/3-octave spectrum analyzer for equalization, then it may be just as well to play pink noise from a CD, as you suggested.

The original iPhone has the flattest frequency response on its headset input, so I would recommend the ThumbTacks microphone for your setup.

Ben

gadzby

Thanks Ben for the reply.  So it appears Apple allows the dock input to be used simultaneously with the headphone jack output, but not the other way around.

Thanks for the pointer to ThumbTacks.  Should this microphone be oriented vertically for EQ measurements?

Grant

benfaber

So it appears Apple allows the dock input to be used simultaneously with the headphone jack output, but not the other way around.

That's right. The iPhone (and 2G iPod touch) can tell the differences between headphones (or a stereo connector) and a headset (a four-conductor connector). When the headset is used, input and output are routed through that single jack. If headphones are used, the iPhone looks for input from another source, so you can use dock input and headphone output.

Thanks for the pointer to ThumbTacks.  Should this microphone be oriented vertically for EQ measurements?

The microphone is omnidirectional, but the iPhone (and your hand) will obviously affect that. A vertical orientation, then, should be fine.

Ben

ubxf

Hello,
Sorry if it has been discussed but would it be possible to use a usb mic with the iphone
Thanks
francois

benfaber

would it be possible to use a usb mic with the iphone

The iPhone is not a USB host, so a USB mic can't be used as an input source.

Ben

ubxf

Thanks Ben,
i've been trying to do an analog line in into the iphone dock connector but it's not working. line out
is working fine though but needed some jumper between pins besides the documented output pins.
Is there an undocumented trick to make the line in work?
Thanks
francois

gadzby

Hi Ben:

Can you provide some nominal Ref. Input Level and Input Sensitivity calibration settings for the Thumbtack and Apple earbud/mic devices?

Also, what is the input dynamic range for Thumbtacks and line input?

Thanks,
Grant

gregn

It was noted on the blog that the Belkin TuneTalk Stereo works with an iPhone 3GS running OS 3.0.1.  Is it known to work under OS 3.1.2?

I had a MacAlly iVoiceIII working on an original iPhone running OS 3.0.1, but when I upgraded to 3.1.2, I received two errors messages.  After the second one was displayed stating that "This accessory is not supported by iPhone", the device was disabled.  I observe the same behavior on a 3GS running OS 3.1.2.

I'm considering trying a TuneTalk with SignalScope Pro, but would like some assurance that it will work before I purchase it.

benfaber

It was noted on the blog that the Belkin TuneTalk Stereo works with an iPhone 3GS running OS 3.0.1.  Is it known to work under OS 3.1.2?

Yes.

I'm considering trying a TuneTalk with SignalScope Pro, but would like some assurance that it will work before I purchase it.

It works fine. In fact, the TuneTalk is now the device I typically recommend.

Ben

gregn

Thanks Ben for the fast response.  I look forward to checking it out.

Greg

Simon Logan

Hi Ben,

I've discovered an affordable dock solution for the ipod / iphone that has line in and line out facilities : the Djtech rec-in. I've tested this and both the iphone 3GS and the ipod touch 2G are happy to play music through the line out, and record voice memos via the line in.
However, signalscope pro won't recognise it as a line output device. When you plug it in, it briefly appears as "dock output" in the signal generator before changing to "receiver" (iphone) or "speaker" (ipod).
Do you know why this isn't being recognised? I have ensured that "prefer speaker output" is off.

Thanks,
Simon

benfaber

Simon,

Some devices, including the Alesis ProTrack, do not support simultaneous input and output--these devices were designed for classic iPods rather than for iOS devices. It's possible that this is also true of the DJ-Tech device.

Ben

Simon Logan

Thanks for your response Ben.

That may indeed be the explanation. I'll do some tests on the unit anyway and report back.

Simon