# Please Help with head unit preouts



## judesign (Feb 20, 2011)

Hey guys I recently got new alpine headunit (cde123) which includes three sets of 4v preouts. I already have an amp and sub that are fairly new. I wired and hooked up the headunit and get good sound from the 4 main speakers. Im just not getting any sound at all from the subwoofer although the power light is on.

Can preouts be defective on a new unit?

Things I've tried ; hooked up ipod with rca cable directly to sub and amp and I do get sound. Replaced rca cables with new cables = no change.

Also I have tried the other preouts on the headunit and get no sound from them either. At this point I cant see it being anything else except a bad headunit. Any help is appreciated.


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## Gary S (Dec 11, 2007)

Did you try the front or rear preouts? Is the sub turned on in the head unit menu? Crossovers in the head unit turned on/off? If you try every combination of tuning in the head unit, it certainly could be a defective head unit.

Edit: Where did you buy the head unit?


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## seekingSQnirvana (Dec 21, 2008)

Have you tried testing with a multimeter?


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## radwilsons5803 (Dec 2, 2010)

I would make sure the sub and amp are up to par as well. My buddy had the same problem and it turned out his subs were at fault. They had bad tinsel leads. Try a different sub first, then if problem persists, use a different amp, and so on. What amp are you using?


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## judesign (Feb 20, 2011)

Thanks for the replies. Head unit from crutchfield and they are sending me a new one since they think the preouts are defective. Im just not sure how likely that is but I cant think of what else it could be ( im fairly new to car audio)

I have tried the other preouts and made sure of the rca orientation (polarity). Still no sound. The only preouts on the unit you can turn off are the sub preouts and I have made sure they are turned on. Also the other two sets of preouts are always on and are producing no sound as well.


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## judesign (Feb 20, 2011)

seekingSQnirvana said:


> Have you tried testing with a multimeter?


Im not sure how to do this


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## judesign (Feb 20, 2011)

radwilsons5803 said:


> I would make sure the sub and amp are up to par as well. My buddy had the same problem and it turned out his subs were at fault. They had bad tinsel leads. Try a different sub first, then if problem persists, use a different amp, and so on. What amp are you using?


The sub and amp I am using are both alpine. amp is mrpm500 hooked up to an alpine type r 12. I have been using the sub and amp for a few weeks with a line output converter and factory head unit. They have been working great so Im not sure if they are at fault especially since they worked when I plugged an ipod directly up to them.


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## Gary S (Dec 11, 2007)

I think up to 10% of electronics have some defect out of the box. Not uncommon at all.


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## judesign (Feb 20, 2011)

Ok it gets stranger. Again thanks for helping the newb. I just tried it one last time and am now getting sound from the sub but I have to turn the gain almost all of the way up and turn the headunit sub level all the way up. Im not sure what to set the filters to or if thats an issue.


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## radwilsons5803 (Dec 2, 2010)

Sounds like its the head unit if the amp/sub worked on your ipod. If you ever need any help with using a multimeter just let me know. Hope the new unit works out for you


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## sqshoestring (Jun 19, 2007)

Get a $10 DMM, digital multimeter. You should be able to d-load a tone CD from here and burn it, usb, etc. Play a 1dB tone at 60-80 hz cheap meters like that better, unhook all the speakers and RCA. Ground the black lead and put the red lead inside the RCA outs on the HU. Play the tone at loud as the HU goes or up to where it clips if you know. Have meter set to AC voltage. If its a 4v HU you should see 4v on the meter though it may not, but 2V even will run an amp fine. You will not see much voltage until it is very loud. If you checked the speaker leads you would see 10v or something, but make sure you don't short any speaker leads while doing this. You could probably turn it up that loud for a moment but if you leave your speakers hooked up don't damage them. If you took your ipod RCA cord and checked it iirc they max at 1v AC, the outside shield of the RCA is 'ground' in either unless you have balanced outputs on your HU. Those shields should be grounded to the case of the HU for the HU RCA. That you would measure with ohms setting it should be near 0 or same as touching the leads of the meter. Not all meters show 0 ohms well (complete short).

Note any filters in the HU will affect what it plays, a 100Hz high pass is not going to play 60Hz out the high side RCA plugs. So you may have to turn off the filters or change/etc. The meter may show a 1Khz tone, just that some are calibrated to 50-60Hz because household electric uses that. They may or may not read other voltages significantly different than that, would have to try it. Something like a fluke meter will no problem I mean cheap $10 meters can have problems with it.

I would double check all your gains/levels/settings. The low pass for the subs I use the HU filter if it has one, so it can be used from the driver seat. The amp just turn it off or set it higher where it does not matter....if you run 80 low pass for example then set the amp at 150 and it will have no effect you can even move the HU higher if you ever want to. Note if you have a high pass on your regular speakers and try to run the sub off the front or rear RCA, you will have no bass and must use the sub outs. Usually the HU filters apply to both speakers and RCA outs, though not always you'd have to check the manual.


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## TrickyRicky (Apr 5, 2009)

1-check if the sub ouput is on
2-check your RCA's
3-if your sub output is on and no output is given then the RCA's may be defective on the HU

You can always run your woofer amp with the rear RCA outputs or even front (aslong as your HU is not crossover and no bass signal is there).


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## radwilsons5803 (Dec 2, 2010)

Definately go with the above mentioned posts. All the featues on these units can take some time to get set up properly.


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## judesign (Feb 20, 2011)

fixed. Thanks again for all of the help. I learned alot about troubleshooting this morning.lol. turned out to be a faulty set of rca cables. They must have been at too acute an angle at the old headunit because right at the terminal is where it was cutting out. I just happened to bump it the right way and caught a hint of subwoofer as I was preparing to give up. Got some new rca cables and made some adjustments to the eq on headunit and amp and now it sounds great. Its always something:laugh:


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## TrickyRicky (Apr 5, 2009)

Good to hear. I hate cheap RCA cables. Sometimes is better to make your own. I for one buy hi-end JL Audio and Stinger RCA's, but I buy them when they are on sale.


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