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Making +/- 15V from 2 15V supplies

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slade8200

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I have a pair of computer speakers and on the back where the power plugs in it says +/-15V input (3-pin). The power supply I used to have for them is lost and they were great speaker so I want to use them. I'm thinking of buying 2 15V supplies (typical wall AC adapter type). My question is, will the following configuration produce the +/- 15V I need?

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The central connection jumpering the supplies should also be used as 'common' and fed to the powered speakers.

Observe proper polarity !!! or your speakers will smoke !!! Top trace is +, central trace is 'gnd' and bottom trace for minus in your schematic.
 

The central connection jumpering the supplies should also be used as 'common' and fed to the powered speakers.

Observe proper polarity !!! or your speakers will smoke !!! Top trace is +, central trace is 'gnd' and bottom trace for minus in your schematic.

I didn't think you could do this sort of thing with wall plugs. You cn't do it with PC power supplies either I believe.
 

You should be OK to do it because wall adapters should have isolated outputs. Do be careful to use the same kind of adapters though and to switch them on/off simultaneously or you could be in a situation where one supply is present but not the other.

Brian.
 

You should be OK to do it because wall adapters should have isolated outputs. Do be careful to use the same kind of adapters though and to switch them on/off simultaneously or you could be in a situation where one supply is present but not the other.

Brian.

What happens if you don't switch them off exactly simultaneously?
 

Well, there is a risk of the voltages being unequal which may or may not damage the amplifier, depending on it's design. As it is supposed to have both positive and negative supplies, removing one will undoubtedly upset the DC conditions and may result in capacitors having the wrong polarity across them.

Brian.
 

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