Does anyone know how to remove the electronic hum from a paging speaker?

I've got a 12 watt pager speaker. I took this really old black G3 Western electric Telephone. I've wired them to a 1.8 watt dc power supply for the moment. Does anyone know how to remove the eletronic hum from my PA system? Plan on getting a better power supply soon.

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Your problem is you HAVE to have an amplifier, and you ain't got one. You are probably going to have damaged your speaker by driving darned near DC in it.
thegeeke5 years ago
Hum is one of the hardest things to remove in audio, however, see my instructable "Audio Problems".  Step 2 gives the basics on hum, it's designed from a professional audio engineer's perspective, and it doesn't cover everything that can cause hum, but it should at least get you started on the right track.  Feel free to ask me if you have any questions.
There's a lot it could be. Show your circuit.
playpep (author)  steveastrouk5 years ago
Power source DC 7.2v 250ma
Paging horn 12watt
Sorry my computer wont let me send a picture of circuit.
There are four leads from the telephone handset. Yellow, Green, Red,Black
The power source has two solid black leads (do not know which is positive)
The paging horn has two solid black leads- same case as power source.
I have found that it works if you connect the red lead to one of the black leads of the Paging horn. Then the other black lead of the paging horn is connected to one of the leads of the power source. Then the black lead of the handset is connected to the other one of the power source. I will play around with the wires and see if it helps. I hope you understood what i am describing.
iceng playpep5 years ago
Here is a hum free AC to DC supply filter circuit and a Corcom. . . A
balunXFMR circuit.GIFCorcom.jpg
playpep (author) 5 years ago
How about this. Would Someone mind taking the Information provided and help me write a circuit that will get the most out of the 12 watt horn? Lets say I use a 12v power supply. How could I wire the horn to the current handset mic and have the capability to connect a 3.5mm audio jack?
iceng5 years ago
  • Add a lot more filter capacitance to the DC supply circuit which you neglected to provide.
  • Use twisted pair and electro static shield wire for the long lead wire.
  • Put a Bauln transformer in between bridge and the capacitor in the input power supply.
  • Enclose the electronics in a metal box.
  • Place a Corcom at the ac input of above metal enclosure.
playpep (author)  iceng5 years ago
Well again I am a novice at electronics. I understand that I need to add filters and a bigger power source but right now ive just thrown this together. I can get the wire, Bauln transformer, and metal enclosure.
You lost me At the Corcom thing. And what about the Ac you mentioned? My current power source is DC?
IS there an amplifer involved in this anywhere ?
playpep (author)  steveastrouk5 years ago
No not at the moment. Although i guess I would need one if I wanted the PA to be louder than at the current moment. Or at least get a bigger power source.
Re-design5 years ago
From the sound of it I'd be looking for a more powerful power supply with a bigger capacitor so that the 60 cycle ac didn't cause the hum.
playpep (author)  Re-design5 years ago
I have very basic skills in electronics so could you elaborate on the 60 cycle ac and how big of a capacitor should i get? And how would I then wire the circuit?
playpep (author)  playpep5 years ago
So I did some research and I think you are refering to the 60hz hum? I looked it up and it sounds the same. From what i saw ground loops might be the problem. Am I close or am I way off base?