TASCAM TA-1VP 11LimitingExamine the 99:1 curve in the above graph. This settingreduces all sounds above the threshold to the sameloudness. This is called limiting. Limiting is usuallyemployed to allow a dynamic signal to be recorded at amaximum level with no risk that transient peaks will resultin overload. In this application, the threshold setting(usually set relatively high) determines the extent towhich the peaks will be limited.Dynamic Expansion and GatingSometimes, it is desirable to increase the differencebetween the quietest signal and the noise in a recordingby using a downward expander. A typical applicationwould be eliminating room noises and breath sounds thatcan be heard between the phrases of a recorded vocalpart.The graph below shows the curveÉexpander. Notice that above the threshold, the curvefollows a 1 to 1 ratio (i.e., is unaffected by the gate). Foreach unit of input change below the threshold the outputchanges by two units. This is called a 1 to 2 expansionratio.As the input signal drops below the threshold, its outputlevel drops at twice the rate it would using a 1 to 1 ratio.In effect, sounds below the expander threshold are “fadedout” more quickly than they would be normally.OUTPUTLEVELINPUT LEVELLOUDERLOUDERTHRESHOLD1 TO 2 EXPANSION RATIO1 TO 1 RATIOWhen expanders use ratios higher than 1:10, soundsbelow the threshold are faded out very rapidly. This effectis called gating and can sound very abrupt. Adjusting thegate ratio can smooth out the abrupt change. The graphbelow shows the input/output curve for a typical gate.OUTPUTLEVELINPUT LEVELLOUDERLOUDERTHRESHOLD1 TO 99 EXPANSION RATIO1 TO 1 RATIOSounds that are louder than the threshold get “throughthe gate” unchanged. Sounds that are below thethreshold are not heard. Gates can be used to greateffect in processing drum tracks where sounds from theother instruments in the drum set leak through the mikeof the instrument being recorded. Gates are also usedfrequently to “gate off” a reverb tail or the ringing from aninsufficiently damped drum head.Compression and ExpansionCombinedThe TA-1VP allows you to use both compression andexpansion simultaneously. This ability is useful in tamingthe typical problems that arise when processing vocaltracks. The graph below illustrates the use of compressionwith a downward expanding gate.OUTPUTLEVELINPUT LEVELLOUDERGATE THRESHOLDCOMPRESSOR THRESHOLD1 TO 99 EXPANSION RATIO4 TO 1 RATIOUsing this setting, levels above the compressor thresholdwill be compressed at a 4 to 1 ratio. Levels below thecompressor threshold but above the gate threshold willnot be changed. Levels below the gate threshold will begated out completely.2 – Introducing the TASCAM TA-1VP Vocal Producer
