These specifications are subject to change.
The microphone is a 1/2″ nominal diameter, omni measurement microphone. iAudioInterface provides two ranges, 30dB SPL to 105dB SPL, and 50 dB SPL to 130 dB SPL. Ranges are selected from within AudioTools, and most functions will auto-range the microphone to provide a full 30 to 130 dB SPL coverage. Other apps have access to one gain range only, that can be selected from within AudioTools.
The microphone appears at the left input of the iPod touch.
Range Noise floor to clip level Frequency Response
Low Range 30 to 105dB SPL 20-20k +/-3dB typical
High Range 50 to 130dB SPL 20-20k +/-3dB typical
Mono Balanced Line Input
The balanced line input has three ranges: low, which covers -90 dBU to -15dBu, mid, -70 to +8.0 dBU, and high, -45 dBu to +40 dBu. AudioTools will auto-range the line input as appropriate. Other apps will have access to any one line input range. This range may be selected from AudioTools.
The balanced line input is presented to the iPod touch’s right input.
Range Noise floor to clip level THD (-1dBFS) Frequency Response
Low Range -90 to -18dBu .015% 20-20kHz +0.0 -0.1 dB
Mid Range -70 to +8dBu .010% “
High Range -45 to +35 dBu .015% “
Stereo Line Input
When the line input jack is configured as a balanced line input, it can be configured to use any of the 3 input gain ranges listed above. When configured in AudioTools, iAudioInterface will remember it’s settings even through power-off.
The output can be switched from stereo, the default mode available to all apps, to a true balanced output, which uses the left channel as the source, from AudioTools. A level control is provided that controls both the stereo and balanced output level. By default, the level control is bypassed, but may be enabled from within AudioTools.
Both of these settings may be set from within AudioTools, and are stored in non-volatile memory so they will be retained even after removing power from iAudioInterface.
Noise floor to clip level (balanced) THD (-1dBFS)
-60 to +12dBu .010%
In stereo mode, which is the default mode available to any app, including iTunes, for example, the maximum output level is +6.0dBu.
In balanced mode, the output level can reach +12dBu. In AudioTools, some functions internally route the output level back to the line input, to monitor the actual loaded output level.
iAudioInterface is powered directly from the iPod touch. When used for normal music playback, it consumes about 40ma of current, on average. When driver a low-impedance load, and producing a full-scale sine wave signal, current rises to 60ma average.
In actual use tests, iAudioInterface has only a minimal impact on the run time of an iPod touch.
Using the mini-USB jack, you can power the iPod touch with any USB power source, including any of the USB batteries. Also, the USB port is fully functional and can be used to sync the attached device.