Martin Audio – MA1.3s Amplifier
E
NGLISH
9
the fans then blow at high speed before going into "idle". The two bottom green LEDís then illuminate to show the
amplifier is operational.
6.4 Denmark:
National deviation concerning installation of the MA1.3s:
Danish safety regulation only permits the use of an 8A main fuse. As the MA 1.3s uses an internal primary mains
fuse of 15A, the MA1.3s must be equipped with an industrial mains connector rated for 16A or above, or as an
alternative it can be hard wired to a 16A capacity circuit and breaker.
6.5 Grounding
There is no ground lift switch or terminal on this amplifier. The signal ground is always floating via a resistor to
chassis and the grounding system is automatic. If a potential difference above 0.6V is detected between signal
ground and chassis ground, a short circuit is automatically introduced between the two, ensuring electrical
protection. If other equipment or amplifiers within a system should develop an electrical fault to earth, the mains
fuse on that equipment should rupture due to this automatic system, allowing an earth current to flow for protection
purposes.
If however you wish to permanently connect the signal ground to chassis earth, connect the XLR-connectorís shell
lug to pin 1. In the interest of safety never disconnect the earth pin on the mains cable.
To comply with CE approval (radio interference), there is an AC mains filter. This filter needs the chassis ground for
reference, otherwise a current loop is formed via the signal ground.
Never disconnect (lift) the mains safety earth
.
6.6 Power
consumption
There are three ways to determine the power/current consumption of the amplifier:
First
, the peak current draw at full output power. Under this condition the power amplifier will operate for less than
2 minutes before thermally limiting or blowing the mains fuse, and is an unrealistic ënormalí use condition. To
design a mains distribution system based on the current draw at full power would result in an over specified
system. No programme material requires the full steady state continuous power of an amplifier. This operating
condition is only used for amplifier bench testing.
Second,
the maximum expected average current under worst-case program material, which is 1/3 of full power
according to the FTC-standard. At this level the music will be in a state of constant clip and is therefore the highest
power level that can be obtained without completely obliterating the program material.
Last
, the "normal operating power", as defined by EN 60065, IEC 65/ANSI/UL 6500 as a measurement level for
approval and testing to these standards. The normal operating power is measured using pink noise, with an
average output power equal to 1/8 of full power. The one-eighth power is the maximum level music can be re-
played without continuous amplifier clipping; this corresponds to headroom of only 9dBs, which is very low for
normal program material.
6.7 Calculation
The current draw
can be calculated by dividing the mains input power by the mains voltage.
Power
1/3 Power
1/8 Power
Idle
[W]
note 1
note 2
MA1.3s
8 ohms
2x
350
630
400
110
4 ohms
2x
650
1120
700
110
2 ohms
2x
1100
1975
1185
110
note 1
Average power with music as program source. The amplifier driven to clip level.
note 2
Normal music power with 9dB headroom, IEC standard power rating.
MAX OUTPUT POWER
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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