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PA Speaker Line Test Circuit

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Suraj143

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Guys I need to make a simple circuit to test 100V speaker lines. The speaker line has 10-20 speakers (100V/6W speakers).

Going to use NE555. Please tell comments or modifications to my circuit.
 

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spec

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Hy Suraj143,

With your circuit you will be asking the 555 to deliver 12A/8 Ohms= 1.5A. This will either blow the output stage of the 555, which can only supply 200mA, or overheat the 555 and destroy it.

You have two choices.

(1) Put a 56 Ohm resistor in series with the transformer which will generate around 320 mW.

(2) Design a different circuit which can drive the transformer at 12V.

It would be better in any event to drop the 555 supply voltage to 5V.

You will also need a couple of catching diodes on the output.

spec
 

audioguru

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What do you want to test? A PA system uses an amplifier. Use the amplifier with an input signal to test the speaker lines.
 

Suraj143

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Guys I made the circuit.The problem is the output is very low.How to increase the output power?Need to do this with very limited parts :)
 

audioguru

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Guys I made the circuit.The problem is the output is very low.How to increase the output power?Need to do this with very limited parts :)
You need an audio amplifier with a powerful output transformer to drive the 100V line. Usually a PA system has the amplifier. The 555 circuit simply produces a low power square wave that sounds like a buzzer. It can feed the audio amplifier.
 

alec_t

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What test are you trying to do? Continuity? Voltage drop? Impedance? .....?
 

audioguru

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Since he said Speaker Lines (many of them?) instead of line (singular) then I think he needs to test which line goes where, or if a line has no speakers on it (why not use an ohmmeter then?).
 
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