TL Audio A2 - Manual (Page 10)

9
OPERATION.
Input Gain stage
The input gain sets the levels of the line level signals coming in to the Ebony A2.
Increasing the input gain control setting will also have a pronounced effect on the
amount of compression, as the threshold will remain constant as the input level
increases. If the input gain is adjusted the threshold can be re-adjusted accordingly to
maintain a similar amount of compression.
Tube Stage Drive and Peak LEDs.
These LEDs indicate the drive level to the tube, or valve, stage. The Drive LED is a
variable intensity indicator, starting to glow when the tube harmonic distortion is
around 1%, and being fully illuminated at approximately 5% harmonic distortion. The
distortion is predominatelly second harmonic, unless very high drive levels are used,
in which case the tube is eventually pushed into harsher saturation, indicated by the
tube Peak LED.
What is Compression?
Compression is an essential but often misunderstood process in modern recording. Put
simply, compression reduces the difference between the loudest and the quietest levels
of an audio signal. This is known as reducing the “dynamic range” of that signal and is
a powerful tool for an engineer helping to avoid overloading, distortion problems as
well as raising the level of the quieter parts of the audio signal. Before the introduction
of compressors the only way this could be achieved was by “gain riding”, whereby an
engineer would control the fader manually in order to try and anticipate very large
levels (which might distort the signal) or very low levels (which may get lost in noise).
The introduction of compression devices meant that this process could be controlled
automatically, allowing the engineer to get on with more productive jobs!
Many instruments and voices have a very wide dynamic range that need to be
controlled. A singer, for instance, may be singing quietly one moment and very loudly
the next, and unless compression is applied the vocal won’t “sit” correctly in the mix,
in addition to the problems of distortion on loud passages and noise on quiet ones.
Compressors effectively turn down the loud bits and turn up the quiet bits, to achieve a
more even and controllable level.
Compressors are often judged by their ability to control the dynamics without creating
noticeable audible side effects. Heavy compression can cause the signal to pump or
breathe with the onset and release of the compression.
Some compressor designs can dull the signal and lose the top end of the signal. The
Ebony A2 is also capable of more severe compression based around the optional Hard
Knee mode if this is desired.