MIXING AMPLIFIERS
MIXING AMPLIFIERS
5
2
1. Power switch
Turns mains power on and off.
2. Protect indicator
This red LED illuminates when one of the protections have been activated. No or distorted
sound will be heard anymore. This will be in case of overheating being the result of drawing too much power from
your amplifier or the impedance of the speaker lines connected are below the minimum load impedance (see 17).
3. Level indicators/clip-limit
A green LED will light after powering on. To work within normal conditions the volume
indicator should be kept under 0dB (100%). At -2,5dB a limiter will be activated. This red LED indicates that the “auto
gain circuit” keeps the level below clipping. This is NOT a clip indicator, but an indication of the “automatic gain
control”.
4. Microphone 1 input
This balanced ¼” TRS phone jack has been wired in parallel with the other three input options
for microphone 1 at the back.
For normal operation, use only one input at the time for microphone 1, but when useful two microphone inputs of mic 1
can be used together (see note below). Microphone 1 can be given a priority over all the other inputs, except the
emergency input (see 20), by using the VOX priority (see 30).
5. Microphone 1 level control
Adjusts the volume of the microphone connected to one of the four input connectors
(1/4” jack, XLR3, DIN5 or euro block).
6. Microphone 2 3 level control
By turning each control clockwise the desired level of that input in the total mix is
set. To decrease these levels, turn counter-clockwise. The volumes of the inputs not used (open lines), should be set
fully counter-clockwise. If not, hiss might occur.
7. Microphone 4 / line 4 level control
Adjusts the input signal of the microphone connected to the XLR3 input at the
back or the line source connected to stereo RCA input 4 (for example a wireless microphone, see 27).
8. “Muted by priority” led
This red led will blink when any priority status has been activated (see also 18).
9. Music level control
Here you can adjust the level of the line source selected.
10. Line source selector
Select the desired music source to be heard (AUX, CD or TUNER).
11. Bass control
Adjust as per your taste. In reverberant rooms intelligibility can be increased by decreasing bass.
The centre position gives you a flat response.
12. Treble control
Adjust the level as per your taste or needs. Adding high frequencies gives brilliance to your
sound. High frequency feedback can be removed by decreasing treble. The centre position gives you a flat response.
13. Master level control
Here you can adjust the desired volume of the overall signal.
Important notice: 2x4 = Eight microphones possible!
When you use more than one microphone input at the time, in super markets for instance, it is important to use real
paging microphones (APart MICPAT; MICPACB). These microphones maintain the microphone input impedance
when not switched on. This avoids unwanted noise to come out of your loudspeakers. APart MA mixing amplifiers
accept two APart microphones wired in parallel on each mic input at the time, which can be a very useful tool.
Front panel
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Now you are ready to get the best result on distributing your music and messages to your audience.
Your little giant is like a Swiss knife which will astonish you and many others!
In fact working with 100V loudspeakers is rather simple, when done in the right way.
Each 100V loudspeaker has a 100V transformer which can be set to a certain power,
for example: 1,5 3 or 6W. As the example shows, the sum of all loudspeaker settings should never
exceed the amplifier's power specifications.
Never use low impedance (= 8 ohm) loudspeakers on a 100Volt system, even not one.
More technically: When your paging amp has a maximum output of 125 watts at 100V,
this means that the minimum impedance connecte d should be at least 80 ohm (100x100/125).
To check your loudspeaker lines use a decent
impedance
checker (example AP WM100).
How to deal with 100V loudspeaker systems
1.5 W
1.5 W
1.5 W
1.5 W
3 W
3 W
3 W
10 W
60 W
85 W
1.5
1.5
1.5
1.5
3
3
3
10
60
+
+
+
+
+
+
+
+
=
PAGING
MIC
AMPLIFIER POWER > LOUDSPEAKER LOAD POWER
Any suggestion?
They are well appreciated and eventually rewarded!
Send your ideas or suggestions to
No power:
Check whether the “on/off” switch is in the
on
position and whether the power cord has been inserted properly. If
these two have been checked and still the MA125 remains off, the fuse might be blown.
No sound:
Check all the wires and loudspeaker selectors. At least the master and one source should be turned clockwise.
Check whether the pre amp out is connected to the power amp in. In the worst case your MA125 is in protective mode.
Please check your loudspeaker wiring and loads. Operate your MA125 within normal conditions.
Distorted sound:
Your input signal is too high. Haven't you a line level source connected to a microphone input? You
might also be drawing too much power from your MA125 and the loudspeaker load might be too low (minimum 80 ohm for
100V use).
Check the speaker wiring and load with an impedance tester. Turn down the master level.
Hum and buzz:
Please check your wiring and grounding, maybe you created a ground loop. See that all equipment linked
are drawing power from the same power supply. Your radio might get its signal from the cable radio. In this case you have
created a ground loop and a ground loop isolator between the cable signal and your radio antenna input will be the solution.
Troubleshooting
