The following information was extracted from the Apple AudioVision 14
Display Developer Notes; Pages 32-34.
AudioVision Sound Options Dialog Box
------------------------------------
* The controls in this dialog box are intended for power users.
* When you select an option in this dialog box, it is effective
immediately.
AudioVision Sound Options functions. The remainder of this article
explains the Sound Options dialog box controls.
External Sound Input buttons
----------------------------
These controls allows you to set the levels of the external sound input,
specifically line level and microphone level.
The AudioVision 14 Display accepts 2.0 V and 4.0 V peak-to-peak sound
input signals. When you power up the display initially, the Line Level
button with low sensitivity will be selected. This means that the display
is set to accept the 4.0 V peak-to-peak input.
If your sound input device provides a 2.0 V peak-to-peak signal, the sound
output from the display will seem relatively quiet. To compensate for
this, and boost the level of the sound output, you should select
Microphone Level high sensitivity. Once you have done this, the Manager
saves the setting, which becomes the default unless you change it.
You should generally select Line Level low sensitivity for audio
cassettes, audio CDs, and some Apple microphones. You should select
Microphone Level (high or low sensitivity) for most other microphones.
External sound input plays through speakers and headphones
(Internal microphone disables external sound input)
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During normal operation, you should select "External sound input plays
through speakers and headphones." When this option is selected, the
"Internal microphone disables external sound input" option is also
available.
You should select "Internal microphone disables external sound input" only
when your sound input device is a CD player plugged into the audio input
connector on the side panel of the display.
Note that Internal microphone disables external sound input may only be
selected when External sound input plays through speakers and headphones
is selected.
The CD player typically provides a 16-bit sound input, which is
transferred through the display to the CPU, and then back from the CPU to
be output from the display's speakers or headphone jack. Since the CPU
supports only 8-bit sound I/O, the sound output provided in this way is
distorted and inferior to the original input.
If you select "Internal microphone disables external sound input," the
sound input will be routed directly from the input port to the display's
speakers and headphone outputs, without going through the CPU. This
enables the display to function as a powered speaker system, and ensures
that there is no loss in sound output quality.
If you are recording from the CD (or other sound device) input, the sound
input must be routed through the CPU, and you should select "External
sound input plays through speakers and headphones."
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