need some amp help

Member

23. May 2006 @ 18:10

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hey everyone, ok well iv got 9 subwoofers in my room, and i wanted to add a car amp to one of them. the amp is a knock off i got from a friend for free. its a Panasound 800watt amp for a car. well i power it up and everything through the power plug on the back of my Onkyo TX-SR302 reciever and the LED on the amp lights up showing its got power to it. but then i run the inputs from my reciver from a wire to an RCA into the low input on the amp. and then run the output to my sub, then when i try it out nothing happens, as if its off. any ideas on what to do? thanks

Note: and the sub is for a car

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This message has been edited since posting. Last time this message was edited on 23. May 2006 @ 21:19

AfterDawn Addict

23. May 2006 @ 20:56

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I do not recommend doing what you are trying to do for a few reasons.

First, for you to supply enough 12 volt power for an 800 watt amplifier to work, you are going to need a massively large power supply. A little 1 or 2 amp wall wort isn't going to cut it.

Second, car amplifiers are not designed to be used on home stereo equipment. Car stereo systems run on 4 to 1 ohms of resistence. Home stereos run on 8 to 16 ohms of resistance. So right there your car amp and speakers aren't compatible.

Third, the line level power is completely different. Car stereos use a very high output line level from the car receiver, usually 4 volts. This is to help elimiate interference from engine noise. Home stereo systems use a much lower line level signal, usually between 500 mV and 1 Volt.

And this I don't understand:

Quote:
well i power it up and everything through the power plug on the back of my Onkyo

huh? car stereo amps run on 12 volts DC, and I highly doubt your Onkyo amp has a 12 volt output in the back. Are you connecting you car amp to the 120 volt outlets in the rear??

"I have no particular talent. I am merely inquisitive" - Albert Einstein

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This message has been edited since posting. Last time this message was edited on 23. May 2006 @ 20:58

AfterDawn Addict

23. May 2006 @ 20:57

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btw, your sig is WAY too big. combine a few of those text lines together....

Member

23. May 2006 @ 21:17

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ok ill work on the sig, but ya i am getting power to it from the 120w plug on the back of the onkyo and the LED is lighting up on my amp, and i forgot to add that the sub and box is for a car. many of the subs i have r for cars and i have put them in my room. and iv done this before but with a smaller 120watt amp and powered it with a 9.6volt rc car battery and that worked.

This message has been edited since posting. Last time this message was edited on 23. May 2006 @ 21:19

AfterDawn Addict

23. May 2006 @ 21:23

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well if it works then okay, but car subs aren't designed to be used in a large space such as a room, they're meant to be in a small enclosure.

so are you saying that you are connecting the 120 volt AC outputs from the back of your receiver DIRECTLY into the 12v and ground inputs on your car amplifier???

Member

23. May 2006 @ 21:35

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no, well what i just realized is that i think its only outputting 7.2vold, because i added two blue LED fans in my reciever for cooling, and i used a rc car 7.2 volt charger to plug them into, so i have two fans and then i hooked up the amp to the 7.2volt charger, then into the reviever. so im guessing its only getting 7.2volts right? and 5 of my 9 subs r for cars and they bump. so i think i just need to get more power to it(the amp).

codydog

Member

23. May 2006 @ 22:57

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Just my two cents, but your going to burn your house down. There is a right way and a wrong way. Sure putting car speakers in home boxes is common. But wire 2 four ohm speakers in series to bring it to 8 ohms and use a home amp. But they will be power hungry.

boxwrench

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23. May 2006 @ 23:45

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Ok,I'm just going to add my 2 cents worth...the 7.2 volts you were inputting to the amp was only sufficient to light the led.You need big time 12 volt d.c. high current at least 10 amps (and I mean minimum) just to get that amp to try and deal with the load. Do yourself a favor and buy a plate amp for your sub that can handle a 2 to 4 ohm load. Word of caution...It won't be cheap!

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This message has been edited since posting. Last time this message was edited on 23. May 2006 @ 23:47

Member

24. May 2006 @ 12:35

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ya the 7.2volt thing i kinda figured it wasn't enough power. and the price for the plate amp is no biggy. but also my buddy has a portable 12volt car jumper that runs on a rechargable battery, so i think im gunna try that out. ya i have a plate amp on my 12inch MTX sub.

This message has been edited since posting. Last time this message was edited on 24. May 2006 @ 12:37

AfterDawn Addict

24. May 2006 @ 20:38

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you are playing with fire my friend...I seriously hope that you don't leave those power adapters plugged into your wall when you are not in your room. you may come home from school one day and not have a house anymore. just because its 12 volts doesn't mean its not dangerous. you are SERIOUSLY overloading your little 7.2 volt battery charger, and its just a matter of time before that thing melts. Go buy yourself a nice hefty 30 amp power supply, or get a cheap old receiver from a thrift store somewhere and use that as the amp.

Member

24. May 2006 @ 21:17

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ok man, ya i dont have amp hooked up at all right now, its back in the box till i figure out how to get it working.

AfterDawn Addict

25. May 2006 @ 10:45

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I am glad to see you tinkerng with electronics though...its a pretty fun hobby if you get into it. you're on the right path, you just need to learn about volts and current and resistance to get a basis for how electricity works. there are tons of really good books out there...try ebay or half.com. have fun man...

Member

25. May 2006 @ 14:55

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thanks man