TL Audio 5051 - Manual (Page 13)

The red Peak LED operates as a conventional warning that clipping is about to
occur. The operating level of the entire signal chain is monitored, and the LED
illuminates when there is less than 5dB of headroom remaining. Normal
operation would be to set the input gain so that the drive LED is regularly
illuminating, with occasional lighting of the red Peak LED on transients.
If the input and output gain controls are set to their centre (0dB) positions and
there is no EQ boost applied, the Peak LED will illuminate some 8dB after the
Drive LED has reached its full intensity. However, it is possible to add gain
further down the chain (EQ boost or output level gain), which will cause the
Peak LED to illuminate at a lower level of Drive. This situation implies that a
high level of “clean” signal is present, without driving the valves hard.
4.8
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 5051 compressor design, as with other TL Audio compressors,
uses a technology based around a transconductance amplifier rather than a
VCA design. This transconductance amplifier design is known for being able to
retain the full frequency range and natural character of the audio signal, even
when compressing the signal quite heavily. The Ivory 2 5051 is also capable of
more severe compression based around the optional Hard Knee mode if this is
desired.
There are other benefits of compression as well as just controlling the peaks
and raising the quiet parts, applied properly, it can add punch and excitement