9. If a video signal is being used to trigger the MA250 on and
off, connect good quality short as possible video wire with a RCA
jack to the MA250 “Video Input”. Make sure the music sense
button is OUT.
10. If the music sense or video input is being used to turn the
MA205 on and off, set the “Music Sense” button to OUT. Adjust
the Sens (sensitivity) so the MA250 turns on when quieter sound
passages are playing. Adjust the “Delay” so the MA250 turns
itself off 25-120 seconds after the sound has stopped.
11. Individually adjust the channel gains as required. Ideally,
the gains are fully on (fully clockwise).
12. If the 12 volt trigger is being connected, use a 12 VDC
source (about 35mA) with a 3.5mm mono jack. Knoll PS1202
with a new 3.5mm jack works well. 5 VDC triggers will not work.
Caution: Never listen to sound that is distorted. If distorted
sound is heard, turn the volume down immediately or speaker
and/or amplifier damage could occur that is not covered by the
warranty. If this problem persists, contact your dealer.
User
adjustments
and service:
There are no
user
adjustments on
the MA250.
Your installer
may make
certain gain
level
adjustments on
the rear panel.
Caution: The
MA250 contains
no user
serviceable
parts, so do not
attempt to open
or repair the
MA250. Refer
servicing to a
qualified
technician only
or contact the
factory for
information.
When using music sense only,
adjust Sens so the MA250 turns
on when the source music is at
a medium low volume. Sens is
not used for video on or trigger
on. For video sensing without
music sensing turn Sens fully
counterclockwise.
After MA250 is on,
Delay is adjusted to
turn off MA250 after
the source music ends.
Ideal delay adjustment
is about 20-40 seconds.
Delay is used with video
on and music sense only.
Adjust the gain
when the system is
on. Best signal to
noise ratio is when
MA250 gains are on
full (clockwise).
The music sense (auto turn on when
music is present) button should be
OUT (active) when the MA250 power
is to be triggered either from music
sense or the composite video signal.
The music sense button should be IN
when the amp is turned off and on from
the front panel switch or the 12 VDC
trigger.
Connect this 3.5mm
trigger jack if the
MA250 is to be
triggered on when a
12 VDC signal is
present. Polarity
can be reversed.
It needs about
35 mA.
Connect the “TO SPEAKERS”
to the 4-8 ohm speakers.
Connect the “AMP INPUTS”
speaker level inputs to the
whole house audio system
or other amplifier outputs.
The “AMP INPUTS” pass
directly to “TO SPEAKERS”
when the MA250 isn’t turned
on.
Caution: DO NOT CONNECT BRIDGED
AMPLIFERS or amps that do not have
common grounds to the “AMP INPUTS”
as you may damage the other amplifier.
Connect these
unbuffered stereo
line outputs to
other amplifier
inputs as needed.
Connect a composite
video output from a
VCR, plasma TV, etc.
to the “Video Input” if
the MA250 is to be
trigerred on when a
video signal is present.
Make sure the music
sense button is
switched to the OUT
position.
For video triggering
without music sensing
turn the “Sens” pot
fully counterclockwise.
120 VAC / 1.5 A
POWER
Made in Canada
Fabrique au Canada
Input
R
L TO
SPEAKERS
+ +
Sens Delay L Gain R
12VDC
TRIGGER
INPUT
Knoll Systems
Point Roberts WA USA
Richmond, BC Canada
Output
AMP
INPUTS
Video
Input
Music sense
Out = Active

- -

R
L

MA250

Stereo Amplifier
+ +

- -

R
L
RISK OF ELECTRIC SHOCK
CAUTION
DO NOT OPEN
MA250 REAR PANEL
Ideal speaker impedance is 4-8 ohms.