dbx 128 - Playback with Noise Reduction and Expansion

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results in the audible variation of background noise that is
usually described as ‘‘breathing” or ‘“‘pumping.”’ One way
to adjust the control is to increase the amount of expansion
until it sounds extreme, then back off a little.
3. Set the LEVEL control to a point where the BELOW
THRESHOLD and ABOVE THRESHOLD indicators are
amber during quiet passages and red during loud passages.
The numbers around the LEVEL control refer to the actual
input voltage (the ‘‘threshold”’) at which the 128 decides
whether to expand upward (increase the volume) or
expand downward (decrease the volume and the noise).
When the BELOW THRESHOLD LED is on, the 128 is
decreasing the program level, and when the ABOVE
THRESHOLD LED is on, the 128 is increasing the
program level.
How to Playback Using dbx II Tape Noise Reduction Plus
Expansion
1. Set the 128’s front panel switches and controls as
shown,
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2. Set the COMPRESS/EXPAND control (the amount of
expansion) while listening to the program through the 128’s
expander section. Set the LEVEL control to a point where
the BELOW THRESHOLD and ABOVE THRESHOLD
indicators are amber during quiet passages and red during
loud passages.
2. Set the EXPANSION/COMPRESSION control to
the desired compression ratio.
Note that the control is continuously adjustable from
1.0 (a 1:1 ratio for no effect) to infinity (an infinity to
one ratio for extreme compression), As with the expansion
side of the control, a good way to adjust the control would
be to turn it farther toward the infinity: 1 setting until the
effect seems extreme, then back off a little or adjust for
the desired sound.
3. Set the LEVEL control to a point where the BELOW
THRESHOLD indicator (amber) illuminates during quiet
passages, and the ABOVE THRESHOLD indicator (red)
illuminates during loud passages. The numbers around the
LEVEL control refer to the actual input voltage, the thres-
hold at which the 128 decides whether to compress down-
ward (decrease the volume) or compress upward (increase
the volume). Refer to the glossary for a definition of
“threshold.”
If the contro! is set high (counterclockwise), the pro-
gram volume may decrease somewhat; if the control is set
low (clockwise), the program volume may increase some-
what. The amount of compression that takes place is not
affected by the setting of the LEVEL control and adjust-
ment is non-critical.