Firmware recipe for audio test tone generation
wmb at firmworks.com
Fri May 25 21:15:54 EDT 2007
How to play test tones in Open Firmware:
Using recent firmware (Q2C12 or later):
ok select /audio
ok 400 tone
ok 800 tone
ok 1000 tone
ok 2000 tone
The tone is played first on the left channel, then the right.
Frequencies that divide 12000 evenly have low distortion. Other
frequencies will have distortion to varying degrees because of the
quarter-wave synthesis technique that is used.
The level is pre-set at the highest level that the speakers can handle
before the onset of overload distortion (mechanical clipping, I think;
the amplifier still has some headroom as determined by replacing the
little speaker with a much better one).
If you want to change the level,
ok patch -15 -9 tone \ Changes the output attenuation from the
default of -9 to -15.
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