I have recently been working on a custom sound system in my living room. For the subwoofer, I am using a 1000W amplifier. This is currently running off of a 12V computer power supply that outputs around 650W (The power supply shuts off at a certain volume because of lack of power). I have another power supply (not a computer power supply) that is 500W but has a voltage of 13.5V, not 12. I've read that this voltage is actually better for running car audio equipment and I am using another 13.5V power supply for the head unit to power the highs and mids.

I am wondering if it would be possible for me to connect these two power supplies in parallel to increase the power to this amplifier since they are both safe voltages. Would this be possible? Would I need to use a resistor to match voltages? Or is this just not a good idea altogether?

Update: This is car audio equipment so high power ratings should not be a shock.

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    \$\begingroup\$ All I can say is I pity your neighbours and I'm glad I don't live near you... \$\endgroup\$ – Majenko Oct 1 '14 at 15:53
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    \$\begingroup\$ 650 W is not enough, for a living room!!? Turn down the volume and save your eardrums, and the annoyance of everyone else within 1/2 mile. Geesh! \$\endgroup\$ – Olin Lathrop Oct 1 '14 at 15:55
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    \$\begingroup\$ @Majenko: You don't know if he lives near you. He hasn't filled out the location in his profile. I checked too. I'll assume therefore he does live me and won't help him being a ass to everyone else in the vicinity. \$\endgroup\$ – Olin Lathrop Oct 1 '14 at 16:02
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    \$\begingroup\$ Woah, 12V and 1000 Watts... ~80 amps?? What's the impedance of the sub-woofer? Or is there a switching supply in the amp? Do you have a link or model for the 13.5V supplies? I've connected bench supplies in parallel for more current, but I'm not sure that fixed supplies are so forgiving. A resistor or something (power diode?) for matching would be an idea.. but how much current/ power will it need to dissipate? \$\endgroup\$ – George Herold Oct 1 '14 at 16:04
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    \$\begingroup\$ Well I was suggesting a diode in each power supply line for (maybe) two reasons. The first is to protect the supplies when one gets turned on before the other. and the second is to try and provide some load balancing.. I don't know how well that will work. \$\endgroup\$ – George Herold Oct 1 '14 at 16:35

Let me put this as an answer rather than a continuation of comments.
Adding diode to supplies, something like this. Now you'll want some beefy diodes, maybe 30 to 60 amps. And probably Schottkies, maybe something from this page. With heat sinks. RE: power supply adjustment. Hopefully there is some adjustment so that you can set the voltage for each supply to be about equal. (Actually you'll want the voltage after each diode under load to be equal.) Getting exactly 12V is not important.

I do worry, that I'm giving advice to a musician and not an electronics "geek". I hope you understand what you are doing. Do you have a way to measure the voltage? Do you know why I picked the diodes I did? And why the heatsink?

  • \$\begingroup\$ I'm more of a musician but I do know what I'm doing. I have a multimeter so I am able to measure voltage. I know that I will need a 60 amp diode for the psu and 40 for the fixed because of Power=Volts*Amps. To be honest my original idea was adding diodes but I was hoping someone would say I didn't need to change the voltage. \$\endgroup\$ – Spencer May Oct 1 '14 at 17:47
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    \$\begingroup\$ @SpencerMay - if you connect a 12V supply and a 13.5V supply, in parallel and through diodes, the 13.5V supply, will supply all of the power to the load, until that supply is so overloaded that its output sags to 12V to match the other supply. Most likely, the 13.5V supply will shutdown or die first. \$\endgroup\$ – DoxyLover Oct 1 '14 at 18:26
  • \$\begingroup\$ @DoxyLover so that means dropping the voltage to 12V before it passes through the diode is required? Thanks for that info. \$\endgroup\$ – Spencer May Oct 1 '14 at 18:30
  • \$\begingroup\$ @SpencerMay, 60A and 40A? Hmm you want to get about the same current from each supply. If one is at 13.5 volts and the other 12 V, well the 12V one will do nothing. The diodes will help balance things a little, but only to the ~50mV level. The one issue is that when diodes get hot their forward voltage decreases. Which means the one passing more current gets hotter.. and passes more current. You can mount them near each other on the heatsink to minimize this, but... \$\endgroup\$ – George Herold Oct 1 '14 at 18:32
  • \$\begingroup\$ @ George: Using diodes in series with individual supplies and then paralleling them at the outputs of the diodes is never a good idea unless the tempco of each supply-diode combo is positive. \$\endgroup\$ – EM Fields Oct 2 '14 at 8:49

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