# Connecting car subwoofer with inbulit amp to home stereo



## foyalex (Sep 10, 2009)

Hi, I'm trying to connect my sub with inbuilt amplifier http://www.fusioncaraudio.com/new-z.../active-enclosures-8/enab1120-26-product.aspx to a home stereo or home receiver.

I have powered the sub/amp with a computer power supply, it powers on but when I connect it to the stereo all I hear is a hum.

The sub/amp has red/white RCA inputs and the stereo has a single subwoofer pre out. I have tried connecting the white rca cord into the white rca input of sub and sub woofer pre out of stereo.

Could it be a grounding issue? At present I only have one black wire from the PSU connected to the Sub/Amp ground wire.

Fixes please?


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## aka Brett (Nov 25, 2008)

Hi and welcome to TSG

How large is the psu.. in watts
how many volts are you getting when its hooked up?

many times a hum is the wave produced by ac current.
It is switching back and forth 60 times a second.
The juice has to run through rectifiers to be converted to dc.
As of now we have dc..but it wont be steady due to all of the switching at 60 times a second....Many power supplies now have a switcher that increases the frequency,of switching which helps balance of the 60 hz humm...however the wave still wont be flat
To fix this we use basically a large capacitor...this smothes out the waves of electricity...without it your supply of juice on a graph would look like nothing but uphill and down hill.
The capacitor gives you the average of these hills.

I would like to also point out that 12 for a car battery is almost dead.
Most cars when running are about 13.5 volts to 14.5 volts.

The voltage of a charged battery is about 12.55 to 12.70 volts.
So as you can see running from a psu has low voltage to start off with..

Look at the psu for the watts or amps of the 12 volt output.

Amps times volts equals watts..if the watts isnt listed.

Ok now according to your link the unit comes with a 20 amp fuse,
Therefore in theory we need to have a strong enough psu to blow a 20 amp fuse....30amps is comfortable 25amps is pushing it.
So 30amps times 12vots is 360 watts.
25 times 12 is 300 watts.

You need to hook your voltmeter up while you are using the amp and pcu...dont let voltage fall below 11.5 as it is hard on the amp and not good for a psu to be pulled hard either.

Just a little warning up front...this amp woofer combo will not be quite what it is advertised.

It says it has a 20 amp fuse but can produce 360 watts power.
it will require 18 volts to do such.....so with that we know that they push the numbers as far as they can...also this will be power consumed and not audio power

you will be running 12 volts.........12v times 20a is 240 watts
But some of this is lost as heat ..how much?quite a bit sometimes
About half is a safe number...now we are at 120 watts.

Now beings there wasnt any distortion level listed..........its is basically full power and a flat line rather than music,

Now you can use about 50 percent of an amps max output and still sound decent...now we are down to 60 watts.
We you can have it running on the thresh hold of blowing a fuse all the time..so the gains will be set to prevent such.
You will have about 45 watts of actual audio power.
However if it is a digital amp the number will be close to double...so you are looking at from 45 to 80 watts


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