MA400
Series 2
User Guide
User Guide MA400
Installation
Connect the MA400 to the mains supply (nominally 230V AC). If using a British
13 Amp mains plug (to BS1363A), fit a 13 Amp fuse in the plug. (If a 5 Amp fuse is
fitted, it may blow due to the surge at switch on. The MA400 has a 5 Amp fuse on
its front panel, but this is an ANTI-SURGE type. Mains plug fuses are not
anti-surge types.) Connect the wires to the plug as follows:
l Brown = live
l Blue = neutral
l Green/Yellow = earth
l The MA400 must be earthed.
NEVER disconnect the earth, even in an attempt to prevent ‘hum’. If the
earth were disconnected, it could result in equipment connected (even indirectly
through a mixer) to the input, such as microphones, becoming live in the event of
a fault (such as a liquid spillage into the amplifier) The MA400 circuitry is only
“loosely coupled” to earth so is extremely unlikely to be the cause of a “hum loop”.
Install the MA400 away from sources of moisture; avoid areas where drinks can
be spilled onto the amplifier as this may cause serious damage.
The MA400 requires a "line level" signal. This is the signal level from a mixer, a
CD or tape player, or the audio output from a video player or satellite TV receiver.
This signal level is generally referred to as 0dBm or 775mV. A signal from a
microphone, electric guitar or turntable is not suitable; neither is the speaker
output from another power amplifier, which may cause damage to the MA400 if
connected to an input. A signal of 775mV RMS (0dBm) is required to achieve full
power output with the volume controls set on maximum.
Connect the input signal to the ¼” mono jack socket on the rear panel. If
connecting from a stereo output, use a ¼” stereo jack plug to two ¼” mono jack
plugs splitter lead. The input to the left channel is located towards the right of the
amplifier when viewed from the back. Two connectors are provided for each input,
to allow the input signal to be connected to another amplifier as well, by
connecting a mono jack-plug to jack-plug lead fromthe spare socket to the input of
the other amplifier.
Connect the speakers to the output XLR connectors. (XLR connectors are wired
to British Standard BS5278, pin 2 signal (“hot”), pin 1 ‘ground’.)
Any number of speakers may be connected to each channel, as long as the
combined impedance is not less than 4W. Two connectors are provided for each
channel; the speaker loading applies per channel regardless of which of the two
sockets the speakers are connected to The more speakers that are connected, the
lower the impedance. Connecting too low an impedance may damage the
amplifier.
If one of the outputs is not being used, it is not necessary to connect any load to
it.
© N.J.D. Electronics 1996 -Page 3-
MA400 User Guide
For speakers connected in PARALLEL on each channel:
The following combinations MAY be connected
Speakers Combined impedance
2 × 16 W 8 W
3 × 16 W 5.3 W
4 × 16 W 4 W
1 × 16 W,1 × 8 W 5.3 W
2 × 16 W,1 × 8 W 4 W
2 × 8 W 4 W
1 × 4 W 4 W
The following combinations MAY NOT be connected
Speakers Combined impedance
3 × 8 W 2.7 W
4 × 8 W 2 W
1 × 4 W,1 × 8 W 2.7 W
1 × 16 W,2 × 8 W 3.2 W
2 × 4 W 4 W
Speaker Leads
Speaker leads should be chosen with care, especially with a high powered
amplifier. Current carrying capacity is not usually a problem, but the use of too thin
a cble can lead to loss of output. The table below shows the maximum cable
lengths for a 10% loss in output.
NEVER use screened lead to connect speakers to an amplifier, and never
connect the output of the amplifier to a light controller with screened lead: use thin
speaker cable.
Cable size Maximum length for:
4 Wload 8 Wload 16 Wload
0.5mm
0.75mm
1.0mm
1.25mm
1.31mm
1.5mm
2.5mm
2
2
2
2
2
2
2
2.3m 4.6m 9.2m
3.5m 7.0m 14.0m
4.7m 9.4m 18.8m
5.85m 11.7m 23.4m
6.0m 12.0m 24.0m
6.75m 13.5m 27.0m
11.4m 22.8m 45.6m
Ventilation
ALWAYS ensure that an adequate flow of cool air is available at the air
intakes at the sides, and that the hot air exhaust on the front panel is not
obstructed. If the amplifier overheats the speakers will be disconnected, and both
green and red LEDs will go out. If the amplifier is adequately ventilated, this will
not happen during normal use.
If the amplifier is installed in a cupboard, make sure that there is an adequate
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User Guide MA400
supply of cool air, and that hot air from the fan exhaust is not recirculated back to
the air intakes.
The fan and air vents should be cleaned periodically to remove dust and smoke
fluid residues.
NEVER install the amplifier in a sealed cabinet.
Operation
ALWAYS connect the speakers and turn the volume controls to zero before
switching on; do not touch the speaker outputs whilst the amplifier is running as
this could result in electric shock.
Set the input level controls so that the red “clip” LEDs only illuminate on the
loudest peaks when the levels on the mixer are at their highest setting.
If the amplifier is being asked to produce more power than it can supply it will
‘clip’ the signal, and if this happens the red LED will be illuminated. In this state,
the amplifier can produce an output in excess of 300 Watts at levels of distortion
up to 30%, which could cause damage to speakers. This distorted signal has a
large amount of extra treble which can damage high frequency units.
If the "clip" indicators are on excessively there is only one solution, TURN THE
VOLUME DOWN.
When the MA400 is turned off the left channel LED will turn off before the right
channel - this is quite normal.
Choosing loudspeakers.
If the amplifier is likely to be over-driven, then it is advisable to use speakers
which can handle the extra power. Use a 300W 4W speaker, or, if two 8W
speakers are connected to each channel, they should be rated at 150W each.
Using a 200W and a 100W together may result in damage to the 100W speaker,
as they will each receive 150W. NJD accepts no responsibility for damage caused
to speakers by over-driving.
When choosing loudspeakers, always refer to the RMS rating, “music power” or
“peak music power” ratings which are normally between two and four times higher
than the RMS power capability, should be ignored.
When the MA400 is operating normally, the green LED will be illuminated.
If a fault occurs within the amplifier leading to a DC condition on the speaker
outputs, the speakers will be disconnected before any damage can occur. If this
occurs, consult a dealer.
Short circuit protection.
The MA400 is protected against short-circuits on the outputs. If this happens, it
will limit its output current to a safe level until the short circuit is removed. A short
circuit should be removed as soon as it is discovered,as the amplifier is not
intended to be run indefinitely into a short circuit. Short circuit protection does not
protect the amplifier from having too many speakers connected to the output.
© N.J.D. Electronics 1996 -Page 5-
MA400 User Guide
If speaker leads are too long or too thin, their resistance may prevent the short
circuit protection operating in the case of a short circuit at the loudspeaker end of
the lead - in this case the impedance of the cable may be indistinguishable to the
amplifier from a low impedance speaker.
TECHNICAL SPECIFICATION
Dimensions: 19”×3½“(2U)×10” (483×88×254mm)
Weight: 8.2kg
Cooling: Forced air cooling via 80mm low noise
DC fan.
Power output: 200W RMS into 4Wat onset of clipping
120W RMS into 8W
75W RMS into 16W
Max. Output voltage: 112V peak-peak.
Damping factor: 360 at 100Hz into 4W.
Output impedence: 0.005W
Input impedance: 10kW
Input sensitivity: 775mV (0dBm) for 400W into 4W
Frequency response: 15Hz to 30kHz ±3dB
Hum and noise: -93dB
Channel separation: 90dB
Harmonic Distortion: 0.05% at 190Watts into 4W
Intermodulation Distortion: 0.05% at 190Watts into 4W
at 50Hz and 5kHz
Slew rate: 30V/µs
Thermal shutdown: at 100°C power transistor temperature
Power requirement: 230V AC 50/60Hz 400VA
Fuse: T5A HRC 5×20mm
(5 Amp ANTI-SURGE)
Connections: Mains: 0.75mm2cable to BS6500
Input: ¼” jacks
Output: female XLR connectors. (wired to
BS5278)
775mV (0dBm) : 10k
200W : 4
+
120W : 8
Signal Ground
The MA400 complies with EN60065 (Electrical Safety), EN55014 (Electromag-
netic Compatibility) and EN60555 (mains harmonic currents)
-Page 6- © N.J.D. Electronics 1996
±56V peak
© Copyright N.J.D. electronics. Neither the whole nor any part of the information
contained in, nor the product described in thie User Guide may be adapted,
copied, or reproduced in any form except with the prior written approval of N.J.D.
Electronics.
All correspondence should be addressed to:
Customer Support,
N.J.D. Electronics,
10-11, Ascot Industrial Estate,
Sandiacre,
Nottingham,
England.
NG10 5DJ.
Telephone: +44 (0) 115 939 4122
Facsimile: +44 (0) 115 949 0453
Technical Help line: +44 (0) 115 949 0038
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