REAR PANEL
SPEAKER OUTPUT: Push terminals for speaker wire.
PS12: For connection to the power supply.
INPUTS: RCA line level inputs and a balanced XLR mic input for CH1.
MUTE JACK: By shorting out the RCA jack labeled MUTE, the Speaker Outputs
will be muted.
XLR INPUT: For connection to a microphone.
PHANTOM POWER SWITCH: Switches the Phantom Power on or off for a con-
denser mic on channel 1.
FRONT PANEL
CHANNEL VOLUME: Adjusts the level of signal from the Line Input to the Line
out RCA's and Speaker outputs.
3.5mm JACK: For connection to an ipod, MP3 player or computer TRS Stereo
(left, right and ground) connection to channel 4
CONNECTION / OPERATION
To operate the MA251, properly connect cords from the sources to be mixed
(mics, cassette decks, CD players etc.) into the channel inputs. Connect the
speaker outputs to 4 Ohm or higher impedance speakers. Adjust the channel
level controls for the desired volume.
DESCRIPTION
NOTE: THIS MANUAL ASSUMES THE USER HAS A WORKING KNOWL-
EDGE OF AUDIO ELECTRONICS, BALANCED AND UNBALANCED CON-
NECTIONS, AND PROPER SIGNAL LEVEL SETTING.
INSPECTION / WARRANTY
1. Unpack and inspect the MA251 box and package.
If obvious physical damage is noticed, contact the carrier immediately to make a
damage claim. We suggest saving the shipping carton and packing materials for
safely transporting the unit in the future.
2. Please visit our web site at www.rolls.com and click on the Register Your War-
ranty Here button.
CH 4
CH 1
CH 2
CH 3
CH 4
LEVEL
LEVEL
LEVEL
LEVEL
MA251
INPUT
MADE IN USA
0
10
0
10
0
10
0
10
www.rolls.com
CLASS AMP
5 + 5 WATT MIX/AMP
CH 4
CH 1
CH 2
CH 3
CH 4
LEVEL
LEVEL
LEVEL
LEVEL
PS12
CLASS AMP
5 + 5 WATT MIX/AMP
LEFT
RIGHT
MA251
3.5mm
STEREO
+
+
-
-
BOTH OUTPUTS MUST BE USED
PHANTOM
CH 1
INPUT
CH 2
INPUT
CH 3
INPUT
POWER
LINE
OUT
ON - OFF
CH 2
MONO
INPUT
MUTE
R
R
R
L
L
L
PS12
LEFT
RIGHT
+
+
SPEAKER OUTPUTS
PHANTOM
CH 1
INPUT
CH 2
INPUT
CH 3
INPUT
POWER
LINE
OUT
OFF - ON
CH 2
MONO
INPUT
MUTE
-
-
INTRODUCTION
Thank you for your purchase of the MA251. The MA251 is a four channel mixer/
amplifi er designed for Audio and Visual applications. Channels 1 has a micro-
phone XLR input with switchable phantom power. Channel 2 has stereo and
mono RCA inputs. Channel 3 has RCA stereo inputs and channel 4 has a 3.5mm
stereo input. The MA251 is intended for professional applications. It has a
FR4(V94-0) rated glass epoxy circuit board, and a powder coated steel chassis.
All inputs except CH 1 microphone and Ch MONO input are stereo. Outputs for
Speaker and Line are true stereo.
CHANNEL DESCRIPTION
CH 1 INPUT: XLR jack for connection to a microphone. Switchable phantom
power as labeled on unit.
CH 2 INPUTS: Stereo RCA and one mono RCA for connection to a signal source
such as a CD player, cassette deck, tuner, etc.. PLEASE NOTE WITH A MONO
INPUT AS WELL AS A STEREO INPUT, CHANNEL 2 AT CERTAIN IMPED-
ANCES ON THE STEREO INPUT YOU MAY EXPERIENCE CROSS TALK BE-
TWEEN THE LEFT AND RIGHT. THIS IS NORMAL OPERATION AND SHOULD
BE EXPECTED.
CH 3 INPUT: Stereo RCA jack for connection to a signal source such as a CD
player, cassette deck, tuner, etc.
CH4 INPUT: For connection to a stereo 3.5mm(1/8” jack).
LINE OUT: Stereo RCA jacks for connection to a mixer or amplifi cation device.
MU
T
E
+B
+B
+B
MO
N
O
I
N
P
U
T
LINE O
U
TS
VCC
V+
CH 1
CH 4
CH 3
CH2
IN 12-24 VAC/VDC
P4
P100
K
2
3
1
J1
JAPDC
C3
1U
R11
10K
R9
100K
R6
4.7K
C7
1U
R26
10K
R24
1K
R14
10K
R15
10K
R19
10K
R20
10K
R12
100K
R2
3.3K
C6
47U
D2
1N4001
R22
18K
R23 22K
C14
47U
C13
2200
R10
100
R8
10K
2
3
1
4
U1A
4560
6
5
7
8
U1B
4560
R1
3.3K
C8
120PF
C4
120PF
1
2
3
J5
XLR F PC
C10
47U
R7 4.7K
R13
100
1
3
2
P1
A
P
100K
X
2
1
3
2
P3
A
P1
0
0
K
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3
2
P2
A
P
100K
X
2
4
6
5
P3
B
P
100K
X
2
4
6
5
P2
B
P
100K
X
2
4
6
5
P1
B
P
100K
X
2
R5
10K
Q1
2N3904
C28
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+ - -
+
ST
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PHANT
O
M
C29
10U
C1
10U
R3
332
R4
332
+B
R21
4.7K
D1
LDRR
PVCCL
1
SD
2
MU
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3
LIN
4
RI
N
5
BYPASS
6
AG
ND
7
AG
ND
8
VCLAM
P
9
PVCCR
10
PG
NDR
11
RO
UT
12
BSR
13
GA
IN
1
14
GA
IN
0
15
AVCC
16
AVCC
17
BSL
18
LO
UT
19
PG
NDL
20
U2
TP
A
3
122D2N
C20
1K
C23
1K
C24
.1uF
C25
.1uF
C26
.1uF
C27
.1uF
C21
.22uF
C18
.22uF
L1
22uH
L2
22uH
R27
4.7K
R28
4.7K
C19
.68uF
C22
.68uF
VCC
VCC
VCC
VCC
SPEAKER O
U
T
VCC
1
Rolls Corporation
5968 S 350 W
M
u
rray
Utah
84107
1
M
A
251.SCH
A
21 O
c
tober 2009
Tit
le
Si
z
e
:
D
ocument Number:
Date:
Rev
:
S
heet
of
M
A
251 CLASS M
IXER AM
PLIFIER
Rb
VCC
R25
220K
Q3
2N3904
C15
10U
C5
1U
C9
1U
3
1
2
SW
2
SPST
C16
1U
C17
1U
D3
1N4001
D5
1N4001
D4
1N4001
C12
2200
C11
2200
1
2
3
4
J6
P
U
SH TERM
INAL
R16
1K
R18
10K
R17
10K
4
6
J2C
RCAX
4
5
J2D
RCAX
4
1
3
J2A
RCAX
4
2
J2B
RCAX
4
4
6
J3C
RCAX
4
5
J3D
RCAX
4
1
3
J3A
RCAX
4
2
J3B
RCAX
4
2
3
5
4
1
J4
3.5STJK
V+
R29
47K
6
5
7
8
U3B
4560
C31
120P
F
+B
R30
47K
2
3
1
4
U3A
4560
C32
120PF
C30
10U
C2
10U
PHAN
PHAN
V+
R31
100
C33
503
SCHEMATIC
