Acoustic Image + Models - Manual (Page 3)

2
Power
Preamp
Plug the detachable AC power cord into the receptacle on the back of the amp and
into a wall receptacle. A power switch next to the AC connector turns on power to the
pre- and power amps, illuminating a “power on” indicator on the front panel of the
amp. A 6.3-amp fast blow fuse (Contra) or 8-amp fast blow fuse (Coda+, Corus+) is
mounted on the back panel. To replace the fuse, turn off the amp, remove the AC
cord and use a small screwdriver to remove the fuse from the fuse holder. A spare
fuse is included with this manual.
All combos will work with either 115 volt, 60 Hz AC or 230 volt, 50 Hz AC power. A
switch located on the rear panel selects the appropriate voltage. Note that the
correct AC power cord must be used for connection to the appropriate wall plug. If
you do not have the right cord, you can buy one from an electronics or computer
store. Be sure the switch is in the correct position for the intended application.
Please note that units sold in Japan operate at 100 volts only. The above mentioned
voltage switch is not available for these units.
The Contra, Coda+ and Corus+ use combo jacks for the input to each channel of
their preamp. Either an XLR or 1/4 inch connector can be plugged into this type of
jack. The 1/4 inch input has a 1 megohm input impedance that is optimized to get the
best sound from piezo pickups. The XLR input is a low impedance balanced input
with sufficient gain to allow microphones to be plugged into it. The Coda+ and
Corus+ have a switchable 10 dB pad to attenuate the mic level when it is too “hot.”
Phantom power is available through the connector for powering a mic or outboard
Operation at 230 volts with the switch in the 115 volt position will damage the
unit.
Operation of a 100 volt amp at any
other voltage than 100 volts will damage the unit.
Inputs
Refer to the signal flow diagram and the control panel drawings (page 5).
Operation
Contra Rear Panel
Coda+, Corus+ Rear Panel
(shown in docking position)
CAUTION: TO REDUCE THE
RISK OF ELECTRIC SHOCK,
DO NOT REMOVE COVER.
NO USER SERVICEABLE PARTS
INSIDE. REFER SERVICING
TO QUALIFIED PERSONNEL.
CAUTION: TO REDUCE THE
RISK OF FIRE, REPLACE FUSE
WITH THE SAME TYPE 8A FAST
BLOW FUSE (F 8A H 250V)
Fuse
Power
Switch
Voltage Switch 115/230V
AC Input
115/230 V
50/60 Hz
900 Watts
~
Speaker Output 2 min W
1 15V
Speaker Input
8 300W W Headphone
Output
CAUTION: TO REDUCE THE
RISK OF ELECTRIC SHOCK,
DO NOT REMOVE COVER.
NO USER SERVICEABLE PARTS
INSIDE. REFER SERVICING
TO QUALIFIED PERSONNEL.
CAUTION: TO REDUCE THE
RISK OF FIRE, REPLACE FUSE
WITH THE SAME TYPE 6.3A FAST
BLOW FUSE (F 6.3A H 250V)
Fuse Power Switch Voltage Switch
115/230V
AC Input
115/230 V
50/60 Hz
400 Watts
~
Speaker Output 4 min W
Tweeter Switch
On
On
Internal
Speakers
1 15V
Tweeter Switch
On
RMS power:
250W at 8 ohms
400W at 4 ohms
550W at 2 ohms
3
preamp and can be activated using the push button switch located next to the
connector. To avoid an audible “pop”, set the mic input level control all the way off
when switching on the phantom power. An LED indicates when phantom power is
on. The two channels of the Coda+ and Corus+ combos can blended to mix two
instruments, 2 microphones or a mic and an instrument thereby performing much
like a small PA system.
Controls
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
filter and phase reverse in each channel (low cut and phase reverse only in Coda+
and Corus+) and a master level control that affects both channels.
The input level controls the level of the signal at the input stage of the 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 of the unit.
The two controls are provided to allow independent control of “house” volume and
“stage” volume when the unit is used as a stage monitor with a connection to a house
PA. See the discussion under “Direct Out” 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 or Corus 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, small values of
boost and cut are best. The amp is designed with flat frequency response so only
minor corrections should be required to compensate for room effects or “peaky”
pickups in order to maintain the balanced response desired for acoustic instrument
amplification. To minimize electronic noise, avoid operating all controls
simultaneously at their maximum 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 with a maximum boost/cut of
15 dB.
The Contra has a notch/low cut filter, the Coda+ and Corus+ have a low cut filter and
phase reverse switch. The notch/low cut filter is a fixed amplitude, variable
frequency type that inserts either an 18 dB cut or a 12 dB per octave rolloff at
frequencies between 30 and 400 Hz, depending on the position of the control. The
low cut filter is the same in all three models. Approximate frequency settings are
noted on the frequency control. Note that the first half of the control’s rotation affects
Level
Tone
Notch/Low Cut Filter/Phase Reverse