User manual

P1 Audio Processor User Manual Page 25
HIGH PASS FILTER
The high pass filter (sometimes
called a low cut filter) affects only
low frequency sounds below
what’s called the turnover
frequency which in the P1’s filter is
set to 80Hz. When switched into
circuit, it will reduce the level of all
audio components below 80Hz
progressively at a rate of 18dB per
octave, so for example a 30Hz
tone would be reduced in level by
18dB compared to the 60Hz tone
level.
The HI pass filter is in circuit when the yellow led is lit and has
two main uses;
Firstly, to filter out mains hum which gets into the recording chain,
sometimes caused by the use of unbalanced audio connections in
the recording chain, or because the earthing scheme is poor.
Secondly, to reduce the effect of very low frequency noise pick up
through microphones and microphone stands (could be rumble from
traffic noise) or microphone handling noise for those vocalists who
just have to hold on!