TL Audio A3 - Manual (Page 13)

12
30dB Pad.
Occasionally – when using sensitive condenser microphones – the source signal may
be too loud for the input preamp. In this situation, to avoid any overloading or
distortion of the mic preamp stage, the 30dB pad can be used to reduce the input gain
to a more manageable level. The 30dB pad only applies to the microphone input.
90Hz Filter.
The high pass filter switch restricts the low frequency response of the preamp, to
effectively remove rumble of LF noise from the signal. The filter can be useful in
restricting ‘popping’ on vocals or even low frequencies caused by contact with
microphone stands or microphone cables. Popping is an undesirable thump that is
caused by close-miking certain spoken or sung letters, namely “P” or “B”. These
particular letters cause a sudden expulsion of air that can result in an audible thump.
As this thump has a lot of low frequency content the high pass filter can help to reduce
the problem, as can using a pop filter (a device usually made out of nylon material
similar to stockings) suspended in front of the microphone. The 90Hz filter is active
on the mic, line and instrument inputs.
Phantom Power.
+48V phantom power is available at the mic socket, selected by a front switch.
Phantom power should only be used in conjunction with suitable microphones.
CAUTION: Operation of the phantom power switch, or plugging a microphone in or
out with phantom power applied, may cause a click or thump in your loudspeakers.
To prevent this happening, ensure that the system gain is set to minimum (e.g. on your
mixing console fader or power amplifier), before operating the switch or plugging in a
microphone.
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 predominately 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