aussieOC92 Posted February 19, 2011 Posted February 19, 2011 hi im planning to run (in my house) 2x alpine type R subs on my 900watt rockford fosgate amp which requires 12-14.4v at 75AMPS. now i would like to know if i could join together the 3.3v and 12v rails. would this give me a total of 15.3v and the combined amps of 103. the 12v rail puts out 78amps and the 3.3v rail puts out 25. if this is possible could you please reply back. Share this post Link to post Share on other sites More sharing options...
Waco Posted February 19, 2011 Posted February 19, 2011 NO! Do not even try this. You cannot combine multiple rails like that with a computer power supply. At best, it'll shut down. At worst when you load it down it could fry. I'd suggest spending a little and buying an inexpensive plate amp instead of trying to ghetto-rig a PSU to power a DC amplifier. Not only is it a waste (in terms of efficiency) it's generally not good for PSUs to run with only a 12v load on them. Share this post Link to post Share on other sites More sharing options...
Reaper_88 Posted February 19, 2011 Posted February 19, 2011 Thia has "baaaad idea" written all over it.... Share this post Link to post Share on other sites More sharing options...
paulktreg Posted February 19, 2011 Posted February 19, 2011 I can see no reason why a computer power supply shouldn't run with only a +12V load, that's basically what it does anyway. The +5V0 and +3V3 rails are derived from the +12V rail via their own regulators, that's why trying to join them together wouldn't work anyway. There are no minimum currents quoted for the TX950W power supply rails and the specification table gives a maximum combined on the +3V3 and +5V0 of 150W and 936W on the +12V rail but these two together mustn't be more than 950W presuming no load on the -12V or +5VSB rails, so why not pull 936W from the +12V rail and nothing from the 3V3 and 5V0 rails, the specification table implies it is capable. I would like to add that what power supplies say they are capable of doing and what'll they actually do are two different things. Computer power supplies are never actually run in that configuration, there is always a load on the +3V3 and +5V0 rails, fully loading the +12V rail is still running the power supply at more or less 100% of it's rated power which no sane PC enthusiast would do 100% of the time. How often would the amplifier require 75A? Is it run at full volume all of the time? Share this post Link to post Share on other sites More sharing options...
Waco Posted February 20, 2011 Posted February 20, 2011 How often would the amplifier require 75A? Is it run at full volume all of the time? Knowing how he's going to use them I would imagine the spikes in current draw would do more damage than anything else. Running a subwoofer amp would pretty much require zero current most of the time and spike to well over what the PSU can supply for short periods of time. If the amp is rated honestly (which it should be, it's a decent brand), it should be able to pull well over 100 amps when turned up fairly loud with bass-heavy material. I don't think I'd want to waste a good PSU trying to supply that kind of load. Share this post Link to post Share on other sites More sharing options...
paulktreg Posted February 20, 2011 Posted February 20, 2011 He wasn't asking about wasting a good power supply, he was asking if it was possible. Computer switched mode power supplies are about the best you can buy and if a 12V rail is rated at 100A then I'm fairly confident it will do it with very good transient response. What I wouldn't feel happy about doing is running it 24/7 like that! Perhaps he should buy a Corsair AX1200W? Share this post Link to post Share on other sites More sharing options...
panjang110 Posted February 23, 2011 Posted February 23, 2011 he should use an audio capacitor to cope the power surge Share this post Link to post Share on other sites More sharing options...
Waco Posted February 23, 2011 Posted February 23, 2011 he should use an audio capacitor to cope the power surge Waste of money (and dangerous if not wired well and shielded). Share this post Link to post Share on other sites More sharing options...
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