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[SOLVED] Connecting monitor speakers to a mobile phone

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JohnJohn20

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HI. I have just bought some second hand Phonic PS6 monitor speakers to connect to my phone.

So I connected a 3.5 mm jack cable to 2 1/4" plugs for each speaker by taking the common and red wire from the 3.5mm plug to the + and - input of one speaker and the common and white wire to the + and - input of the other speaker.

But there is a lot of 50 Hz hum. The speaker inputs have 3 wires: +, - and GND. I have left the GND unconnected.

So, Is this the right way to connect the speakers?
Should I make up shielded cables where the shield connects to the GND on the speakers.?
Would the shield then be left unconnected at the 3.5 mm plug end?

What do you think is the best way to connect these speakers? Cheers
 

Knowing nothing about these speakers, and a google search that turned up nothing makes this hard to answer. Are these powered speakers? Maybe just try a shielded cable and see what happens-it can't hurt.
 

Knowing nothing about these speakers, and a google search that turned up nothing makes this hard to answer. Are these powered speakers? Maybe just try a shielded cable and see what happens-it can't hurt.

Cheers Barry. Yes, they are powered speakers.

Where should the shield connect to? The speaker GND or the 3.5 mm common?
 

Again, I don't know anything about these speakers. Try connecting both ends or either end to shield,
 

Hi,

If the speakers have "+", "-" and "GND" inputs, then most probaly thus is an symmetric/differential (XLR) input.
But the phone has single ended outputs.

The best is to convert the single ended signal to a differential signal close to the phone.

Klaus
 

The usual SE to DE connection is hot wire to + and common to - and GND. It's however useful to check the kind of input stage provided by the differential ended device, may be e.g. audio transformer or differential amplifier. In the latter case, the amplifier's finite common mode rejection causes hum with unconnected ground.
 

OK then Klaus. Can I do that with something like a capacitor or will it need to be something more active?
 

Hi,

No, a capacitor can't invert an audio signal.
Did you do a search for "audio unbal circuit"?

Klaus
 
Thank you Klaus. Those were the key words I needed.

For anyone who is interested:
- Use 2 core shielded cable for each channel.
- at 3.5mm plug. connect i core to left (or right) signal and the other core and the cable shield to the common
- At the speaker input, signal core goes to (+), the core from th common goes to (-) and the shield goes to GND.
- Repeat with the other channel

Thanks all
 

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