True to the Music
Radial Engineering Ltd.
PZ-Pre
™
User Guide
Notch Filter
The notch filter is designed to manage feedback by surgically re
-
moving an offending frequency while leaving the rest of the sound
intact. To find which note is going to feedback first, play ascending
scales starting from your instrument's lowest note.
During your tests, if you hear that a particular note is more prone
to feedback than others, set the NOTCH Q to the NORMAL posi-
tion and slowly rotate the NOTCH control to see if you can dial
in the offending frequency. This process is sometimes referred
to as 'notching out'.
When you have found the position on the dial that corresponds
to the frequency that is feeding back, play and hold a chord or
simply let all of the strings resonate. Now, turn the LEVEL control
up some more and see what happens. If the same frequency is
still on the verge of feedback, try setting NOTCH Q to DEEP.
An important point when using the NOTCH filter is that the prob
-
lem frequency will likely change each time you play in a different
venue or change instruments. So experiment and get familiar
with the NOTCH filter functions. This will make sound-check go
more quickly and will reduce the occurrence of feedback when
you are performing!
Setting the Notch Filter
1. Set the NOTCH Q switch to bypass.
2. Test by playing ascending notes on the lowest strings.
3. Focus in on the note that tends to feedback before the rest. If
necessary, increase the LEVEL control to produce a perpetual
feedback ring at this note's frequency.
4. Set the NOTCH Q switch to NORM.
5. While holding the note, turn the NOTCH control until you have
tuned the filter to the same frequency. The notch filter is tuned
when the note decays naturally without feeding back.
6. Increase the LEVEL control until the same note starts to
feedback and then back off the level a little.
7. If more gain is needed, you can switch the NOTCH Q to DEEP
and try increasing the LEVEL control some more.
TIP: At some point, turning up the instrument level will
cause uncontrollable feedback at many frequencies and is
an indication levels should be lowered.
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