Filter
Top Products
3
Controls
Notch/LowCut Filter
The preamp has the following controls in each channel: input level, bass, mid,
treble and effects level. In addition,there is a variable frequency, selectable
notch/low cut filterin each channeland a masterlevel controlthat affectsboth
channels.
The input level controlsthe levelof the signal at the input stage ofthe preamp.
The master volume controls the level of the signal at the output of the preamp
(at the input of the power amp). Set the master control at “12 o’clock” and the
input level at zero. The input level should then be used to control the overall
output ofthe unit.The twocontrols areprovided to allowindependent controlof
“house” volume and “stage” volume when the unit is used as a stage monitor
witha connectiontoa housePA.See thediscussion under“DirectOut” below.
The maximum volume at which the system will play is limited by the capability
of the speaker system. A 10-inch driver in a small cabinet has a limitation in
how loudly it will play. If more volume is needed, use a Contra EX extension
cabinet or take a feed from the Direct Out jack to a PA system or another
amplifier.
Each tone control has a center detent at the flat position. Experiment with
settings to achieve the frequency balance that sounds best to you. In general,
smallvalues ofboost andcut arebest. Theamp isdesigned withflatfrequency
responseso onlyminor correctionsshould berequired tocompensate forroom
effects or “peaky” pickups in order to maintain the balanced response desired
for acoustic instrument amplification. To minimize electronic noise, avoid
operatingall controlssimultaneouslyat theirmaximum settings.
The bass control is a shelving-type that affects frequencies below 250 Hz and
with a maximum boost/cut of 15 dB. The mid control affects frequencies
between 300 Hz and 2000 Hz and has a maximum boost/cut of 15 dB. The
treble control is also a shelving-type that affects frequencies above 1000 Hz
witha maximumboost/cutof 25dB.
The notch/lowcut filteris a fixedamplitude, variablefrequency typethat inserts
either an18 dB cutor a 12dB per octave rolloff at frequencies between 30and
800 Hz, depending on the position of the control. Approximate frequency
settings are noted on the frequency control. Note that the first half of the
control’s rotation affects frequencies from 30 to 70 Hz, the last half of the
rotation affects frequencies between 70 and 800 Hz. This is done so that there
isplenty ofcontrolin thecritical lowfrequencyrange.The notchfilteris usedto
Level
Tone
4
Signal Flow Diagram
Contra Control Panel
LevelLevel Bass Mid Master
Direct Out
Treble
Send
Return
Effects
Loop
Notch Cut
OnOff
Freq
Input
Mute
Ground
lift
Post
EQ
Off On
Phantom
Filter
30
70
800
Power
Bass Mid Treble
N/C Switc
Notch
Input
buffers
Input
level
3 band EQ
Filter
switch
Filt
e
Preamp
Phantom power
XLR
input
¼inch
input
Combo jack
Cut
Ch2input,EQandfilter
(sameasCh1below)
Pre EQ
outputs