# Help! Amp turns on normally but no output to sub?



## ShamDub (Oct 18, 2002)

Recently I noticed that my car didn't seem to be putting out any bass. Well, I check the sub and it wasn't doing anything. I figured I had blown it but I've since tested it on a friends car and it works perfectly fine. So this kind of narrows it down to the amp. The normal status light is on. The power, ground, and speaker wires are all connected correctly. Is there any reason why the amp isn't producing any output? (Xtant 300w Amp to Boston 12") I've been running this setup for about a year and a half and my knowledge of car audio is limited. TIA.


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## Realtech (Jan 18, 2004)

*Re: Help! Amp turns on normally but no output to sub? (ShamDub)*

1) put a test spkr on the amp, you can buy a cheapo spker from radio shack. diconnect the box and touch the wires to the test spkrs terminals. if it makes noise, the box wiring or spkr is bad. if you have a multmeter, mesure the impedance of the spkr. Make sure the spkr wire runing from the amp to the spkr is not shorted to ground. this would cause the amp to go into protection, and give no output.
2) some decks w/ subwoofer line ouput, (alpine) will shut of the sub output signal when the battery in the car drops below 9volts. The default programming for the subwoofer output is OFF. After battery voltage is restored, you usually need to reprogram the line level outputs (turn on the sub output)
3) you may have a bad rca cable. This sounds gross, but try this: unplug the signal cables from the amp only, plug in a spare set(to the amp inputs)... turn on the system... with the amp turned on, and the box hooked up(assuming you passed the first test), lick you finger and tap it across the ends of the signal cable that is plugged into the amp. If the amp is good... the static electricity from your finger/spit combination will make the sub "thump". If the amp is broken you will hear nothing at all.
4) If you pass test #3; plug the original signal cables back into the amp. Unplug the other end of the signal cables at the back of the HU. Do the aforementioned spit test... If the spkr thumps again, the cable is good, the amp and spkr are solid, so the deck is not producing a signal. Check the deck.
This sort of problem can become confusing during the tests. some people use a checklist... it's important to be methodical. There's no magic to it.
Oh yeah, and finally, open the top plate on the Xtant amp. There are sockets for upgrade modules inside the amp. these modules look like miniture PCI circuit baords from a PC. They can be x-overs, Parametric EQ's or bass boost modules, they even make a remote gain control for the amp. Once in a blue moon these one of these modules or a jumper inside the amp will work itself loose and the amp will have no output. be careful with the screws that hold the plate on, they like to strip out easily.


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## ShamDub (Oct 18, 2002)

*Re: Help! Amp turns on normally but no output to sub? (Realtech)*

Thanks for all your help...I'll go after all of this tomorrow. Too bad it's like 18 degrees.


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## rknail (Apr 4, 2002)

*Re: Help! Amp turns on normally but no output to sub? (ShamDub)*

Just because the led on the amp comes on does not mean the amp is turning on. 
I would be willing to bet that you blew the fuse under the hood by the battery.
Good luck, let us know what it was.


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## ShamDub (Oct 18, 2002)

*Re: Help! Amp turns on normally but no output to sub? (rknail)*

I think you may be right. The amp never develops any temperature and is always quite cold of the weather. I just went to check the fuse and when I popped the hood I noticed that one of the rubber hoses for oil was nice and split with steam coming out....so I think I gotta fix that first but it should take too long then I'll get back to this.


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## Non_Affiliated (Feb 12, 2002)

*Re: Help! Amp turns on normally but no output to sub? (rknail)*


_Quote, originally posted by *rknail* »_Just because the led on the amp comes on does not mean the amp is turning on. 
I would be willing to bet that you blew the fuse under the hood by the battery.
Good luck, let us know what it was.















Um if the LED is on then the amp is turning on. A amp will not power up if a main fuse or the amplifier fuse is blown.
I would look at how the speaker is hooded up. Did you build the box and install the sub, or did you buy the box and sub together. I would say pull the sub and check out the connections.


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## ShamDub (Oct 18, 2002)

*Re: Help! Amp turns on normally but no output to sub? (ShamDub)*

Welp, I tried plugging another speaker and I replaced the inline fuse, neither did anything. I tried the RCA tap on the other end manuever and again nothing came out. I guess it's dead







but I'm pretty sure I might have a warranty going on it.


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## Realtech (Jan 18, 2004)

*Re: Help! Amp turns on normally but no output to sub? (Non_Affiliated)*

Before you go any further, use a voltmeter or a test light to check for power at each connection along the power wire. 
if you have voltage at the battery side of the fuse holder and none (OR very low voltage) on the other side of the fuse, the fuse is bad. I usually start at the amp and move toward the battery until I find 12Volts.
The Back feeding thru the remote turn-on circuit is rare in Xtant amps. Not unheard of, but rare.


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## Realtech (Jan 18, 2004)

Sounds like ya let the magic smoke out of the box. Once you do that it never works right again. Take it in the the dlr and have it bench checked.


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