MA252
20 + 20 watt
Mixer/Amplifi er
Connection guide
Salt Lake City, Utah
09/11
• RCA Inputs, XLR Mic with Phantom Power
• Volume controls for each Channel
• Low noise, effi cient operation
• Small compact size
• Class D high effi ciency amp
The MA252 is a very compact 20 + 20 watt high effi ciency amp
with a four channel stereo mixer built in. Left and Right stereo
speaker outputs. The unit is perfect for small speakers in small
environments. Great for in ceiling and projector applications where
small size is needed along with class D low radiated heat loca-
tions.
WARNING:
WARNING:
THE MINIMUM SPEAKER IMPEDANCE IS 4
OHMS EACH.
IF YOU CONNECT AND USE THE MA252 WITH A LOW-
ER SPEAKER IMPEDANCE THAN LISTED ABOVE
YOU WILL DAMAGE THE UNIT AND POSSIBLY OTHER
EQUIPMENT THAT IS CONNECTED TO THE MA252.
CH 4
CH 1
CH 2
CH 3CH 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
CH 4
CH 1
CH 2
CH 3CH 4
LEVEL
LEVEL
LEVEL
LEVEL
LEFT
RIGHT
INPUT
+
+
SPEAKER OUTPUTS
PHANTOM
CH 1
INPUT
CH 2
INPUT
CH 3
INPUT
POWER
LINE
OUT
OFF - ON
CH 2
MONO
INPUT
MUTE
010
010
010
010
-
-
PS24
HI CLASS AMP
20 + 20 WATT MIX/AMP
MA252
MADE IN USA
www.rolls.com
SPECIFICATIONS:
Line Input Impedance: 10K Ohms Line
600 Ohms Mic.
Power Output: 20 Watts X 2 (4 Ohms)
Voltage Gain: 55 dB Mic
30 dB Line
Maximum Supply Voltage: 24 VDC
THD: .05% typical
EIN: 3 mV
Effi ciency: 85%
Input Sensitivity: 28 mV
Bandwidth: 20Hz - 25 kHz +/- 3dB
+Size: 6.75" x 3.5" x 1.5"
Weight: 1 lb.
REAR PANEL
SPEAKER OUTPUT: Push terminals for speaker wire.
PS24: 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 LEVEL: 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 MA252, properly connect cords from the sources to be mixed (mics, cas-
sette 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 MA252 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 3CH 4
LEVEL
LEVEL
LEVEL
LEVEL
INPUT
010
010
010
010
HI CLASS AMP
20 + 20 WATT MIX/AMP
MA252
MADE IN USA
www.rolls.com
CH 4
CH 1
CH 2
CH 3CH 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
LEFT
RIGHT
+
+
SPEAKER OUTPUTS
PHANTOM
CH 1
INPUT
CH 2
INPUT
CH 3
INPUT
POWER
LINE
OUT
OFF - ON
CH 2
MONO
INPUT
MUTE
-
-
PS24
INTRODUCTION
Thank you for your purchase of the MA252. The MA252 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 MA252 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.
MUTE
+B
+B
+B
MONO INPUT
LINE OUTS
VCC
V+
CH 1
CH 4
CH 3
CH2
IN 12-24 VAC/VDC
P4
P100K
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
P1A
P100K X2
1 3
2
P3A
P100K X2
1 3
2
P2A
P100K X2
4 6
5
P3B
P100K X2
4 6
5
P2B
P100K X2
4 6
5
P1B
P100K X2
R5
10K
Q1
2N3904
C28
47U
+ - - +
STEREO
PHANTOM
C29
10U
C1
10U
R3
332
R4
332
+B
R21
4.7K
D1
LDRR
PVCCL
1
SD
2
MUTE
3
LIN
4
RIN
5
BYPASS
6
AGND
7
AGND
8
VCLAMP
9
PVCCR
10
PGNDR
11
ROUT
12
BSR
13
GAIN1
14
GAIN0
15
AVCC
16
AVCC
17
BSL
18
LOUT
19
PGNDL
20
U2
TPA3122D2N
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 OUT
VCC
1
Rolls Corporation
5968 S 350 W
Murray Utah84107
1
MA251.SCH
A
21 October 2009
Title
Size: Document Number:
Date:
Rev:
Sheet of
MA251 CLASS MIXER AMPLIFIER
Rb
VCC
R25
220K
Q3
2N3904
C15
10U
C5
1U
C9
1U
3
1
2
SW2
SPST
C16
1U
C17
1U
D3
1N4001
D5
1N4001
D4
1N4001
C12
2200
C11
2200
1
2
3
4
J6
PUSH TERMINAL
R16
1K
R18
10K
R17
10K
4
6
J2C
RCAX4
5J2D
RCAX4
1
3
J2A
RCAX4
2J2B
RCAX4
4
6
J3C
RCAX4
5
J3D
RCAX4
1
3
J3A
RCAX4
2
J3B
RCAX4
2
3
5
4
1
J4
3.5STJK
V+
R29 47K
6
5
7
8
U3B
4560
C31
120PF
+B
R30
47K
2
3
1
4
U3A
4560
C32
120PF
C30
10U
C2
10U
PHAN
PHAN
V+
R31
100
C33
503
SCHEMATIC
-
1
-
2
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