Operation Manual

Chapter 6. Sound Settings 52
amplify the signal so that the loudest possible signal after compression will be just
under the clipping limit. This is desirable because the compressed signal without makeup
gain is quieter than the input signal. Makeup Gain in Auto restores the signal to the
maximum possible level and brings the quieter audio up with it. This is what makes it
possible to hear the quieter audio in noisy environments.
The Ratio setting determines how aggressively the compressor reduces gain above
the threshold. For example, the 2:1 setting means that for each two decibels of input
signal above the threshold, the compressor will only allow the output to appear as one
decibel. The higher the ratio, the harder the signal is compressed. The ratio setting of
Limit means essentially a ratio of infinity to one. In this case, the output signal is not
allowed to exceed the threshold at all.
The Knee setting determines how abrupt the transition is from a non-compressed
signal to a compressed signal. Hard Knee means that the transition occurs precisely at
the threshold. The Soft Knee setting smoothes the transition from plus or minus three
decibels around the threshold.
The Release Time setting sets the recovery time after the signal is compressed. Once
the compressor determines that compression is necessary, the input signal is reduced
appropriately, but the gain isn’t allowed to immediately return to normal levels. This is
necessary to reduce artifacts such as “pumping.” Instead, the gain is allowed to return
to normal at the chosen rate. Release Time is the time for the gain to recover by 10 dB.
The Rockbox manual (version 3.10) Packard Bell Vibe 500