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Old 4th September 2011, 05:38 AM   #1
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Default Car Audio at Home

Hey Guys

I wanted to ask about powering a car audio system at home. I know this question has been asked many times, but I thought I'd ask specific to my case.

Firstly some background information. Basically I have gone and bought the following

Sony Xplod XS-GTF1627
These are 4 Ohm speaker and they have a peak power of 190W and 40W RMS.
These were on sale for $25 bucks a few months back. Couldn't resist for this price, So i bought one.

Jensen Power Amplifier (P400)
This amplifier can provide 75 Watts (RMS) per channel for 4 Ohm Speakers. This is a dual channel amplifier.
In the manual it says it draws a maximum current of 25A (Also has a 25A fuse inserted in the amplifier).
Is my understanding correct? It'll have a average current pull of 6.25A?
P = V*I
75 = 12 * I
I (RMS) = 6.25A (RMS) ?

Nothing special about this amplifier. I bought this purely out of impulse shopping. Got this amplifier for $70.

Automedia AM-3100BT
This is a 50 x 4 Watt (Peak Power) car head unit. In the manual it says it runs on 12V, but it didn't specify what's the rated current. However there is a 10A fuse installed in the Unit, so assuming maximum rated current of 10A.

Just like the car amplifier. Nothing special about this head unit. Just bought it with the car amplifier.

I need to power both the head unit and amplifier. I was looking into purchasing a PSU off ebay (NOT PC PSU!!) to run the entire system. What do you guys recommend for me to do, in terms of powering the whole system?

If a PSU is recommended, is it ok to choose a PSU that is able to provide more current then the system can handle or choose one that will provide less current?

I have looked through ebay for power supplies, like the one below.

350W DC 12V 29A Triple Output Switching Power Supply | eBay
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Old 4th September 2011, 05:50 AM   #2
tomchr is offline tomchr  United States
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Location: Greater Seattle Area
As long as the supply will deliver 12 V, you'll be fine. Actually, battery voltage is closer to 13.8 V, but that's another story. The difference from 12 V to 13.8 V is not worth worrying about. I'm just saying you have a little margin there.

If you get a supply that can't supply the current the amp draws at max power, the supply voltage will sag at the max load and you won't get full power out. The amp will clip and the sound will be horrible (if you haven't blown the speakers by then anyway).

If you get a supply that can supply more current than the amp will draw, that means you have margin. I.e. regardless of how much power the amp delivers to the speakers, the supply will deliver the rated output voltage.

Note, however, that many switchmode supplies require a minimum load for stability. Make sure the current draw of your amp is above this minimum current when the amp delivers no power to the speakers (no sound). With linear (transformer-based) supplies this is not an issue.

~Tom
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Old 4th September 2011, 06:37 AM   #3
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Join Date: Jul 2009
Quote:
Originally Posted by tomchr View Post
As long as the supply will deliver 12 V, you'll be fine. Actually, battery voltage is closer to 13.8 V, but that's another story. The difference from 12 V to 13.8 V is not worth worrying about. I'm just saying you have a little margin there.

If you get a supply that can't supply the current the amp draws at max power, the supply voltage will sag at the max load and you won't get full power out. The amp will clip and the sound will be horrible (if you haven't blown the speakers by then anyway).

If you get a supply that can supply more current than the amp will draw, that means you have margin. I.e. regardless of how much power the amp delivers to the speakers, the supply will deliver the rated output voltage.

Note, however, that many switchmode supplies require a minimum load for stability. Make sure the current draw of your amp is above this minimum current when the amp delivers no power to the speakers (no sound). With linear (transformer-based) supplies this is not an issue.

~Tom
Hey Tom. Thanks for your input. I will power the head unit and amplifier from the same switching power supply. So this should be ok right, given that there is two loads connected to the same power supply?

Do you have any suggestion in how I can go around the stability issue, without resorting to linear PSU's?
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