The Technical Stuff
__________________________________________________________
- 19 -
The
electroluminescent panel utilized in the T4 discharges most of its light very quickly, resulting in an
extremely fast attack time (which can be as low as 10 milliseconds, depending on the frequency of the
incoming signal), Even more critical to the sound of the 2-LA-2 compressor is its signal-dependent
release time. Short transients are released quickly, while longer, more sustained parts of the sound are
given a much slower release. Like the original T4, the T4 in the 2-LA-2 actually releases in two stages:
the initial release generally takes place in about 40- 80 milliseconds (which is relatively fast), followed
by a gradual release that can take as much as several seconds. This kind of program-dependent dual
stage quick-then-gradual release results in a warm and natural sound without the “pumping” which
plagues so many other compressor designs.
The amount of time it takes for the photo-cell to recover after the light is removed depends on how
long light had been shining on it and how bright the light was. This causes something called “memory
effect.” As a result, you can actually “train” the T4’s response characteristics by pre-rolling material
for a minute or two, essentially saturating the photo-cell. Similarly, because the amount of time it
takes the luminescent panel to light up determines the attack, you can “prime” the T4 to light up
faster so that the first note's transient doesn't sneak by too aggressively. To do so, simply have the
musician trigger the compressor by playing a note just before recording begins.
Another interesting phenomenon which affects the threshold (and, to a lesser degree, attack time and
release time) of an electro-optical compressor is “panel aging,” something which is more related to
the amount of actual use rather than age in years. The more “aged” the EL panel, the greater the
amount of gain reduction will need to be applied. Panel aging is probably a major reason why the
same model of electro-optical compressor can sound subtly different between units.
