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Old 2nd March 2004, 04:52 PM   #1
masho95 is offline masho95  United States
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Default Bad HU or Amp??

Ok first off I really don't know much about car audio, that's why I'm here for help. Anyways, I have a Clarion HU and Pyramid 1000 watt PB448X amp. Recently I tried taking the rear speakers off the amp. Since then I haven't had any output at the speaker outputs on the amp. Shouldn't they give a voltage output when working? Also, is there a way to check the RCA outputs from the HU to make sure they are working? (like a voltage output from the RCA's, if so how?) I've tried hooking up the front and rear RCA outputs of the HU to the amp and I still have nothing at the amp speaker outputs. Thanks for any input! I just want to get my car audio sounding half decent again! Also on a side note my car has a stock amp which I am waiting for a bypass cable for. The sound is absolutely horrible with the HU and the stock amp powering the speakers. I've replaced the stock speakers with Infinities, not sure of the models. Thanks again!
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Old 3rd March 2004, 03:54 AM   #2
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I am assuming that you measure no AC voltage across the output(s) of the amplifier. Check the RCA output of the HU by measuring across the two conductors. That is the center dealy and the circle dealy around it.
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Old 4th March 2004, 03:53 AM   #3
masho95 is offline masho95  United States
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Wouldn't it be DC voltage at the speaker outputs of the amp? As well as DC voltage at the RCA outputs at the headunit? I wasn't sure if the RCA's gave a voltage output there or if it was just a very low voltage audio signal outputted. What type of voltage level should I expect to see at the RCA outputs of the HU? Thanks!
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Old 4th March 2004, 04:46 AM   #4
tool49 is offline tool49  Canada
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Actually, you should see AC voltage at the RCA's from the HU. It should be very low, between 1V and 8V depending on the head unit design. The best way to make sure you can actually measure an ac voltage would be to have the HU playing some sine waves really loud (careful about your ears tho)

The speaker output from the amp should also give out some readouts on AC voltage.

Have you checked the fuses on this amp? If not, it is a common cause for dead channels

Hope this helps,
Sébastien
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Old 4th March 2004, 05:59 AM   #5
masho95 is offline masho95  United States
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Well I checked for DC voltage at the speaker outputs at the amp, I was assuming since the car battery puts out DC voltage that it would be the same throughout. I guess I'll check for AC voltage at the HU tomorrow.. I did check the fuse on the amp and the one on the power lead to the amp. Both were fine and the amp wasn't running in protection mode or anything. I'm guessing that something in the amp blew, because stupid as I was I was disconnecting speaker outputs and switching them around without disconnecting the power lead from the battery. Car was off so no remote turn on was on or anything but, the main power lead was still connected. I had also tried using the front outputs of the RCA's from the HU just in case the rear outputs weren't working and the same happened. Before I tried hooking up just the amp and subwoofer and cranked the volume to see if I had anything coming out. With the radio at almost full volume I had a VERY faint source of music coming from the subwoofer. I did take a quick look at the internals of the amp to look for anything blackened but say nothing. Any ideas what may be blown inside if that's the case? Thanks for all the ideas.
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Old 8th March 2004, 11:50 PM   #6
maylar is offline maylar  United States
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Audio is AC. A DC voltmeter won't tell you anything except that your power and remotes are OK, which you need to check first. Measure right across the amp terminals.. from - to + and from - to remote. Should have 12-14VDC at both places.

With the head unit playing music, the RCA cables should show some AC voltage between the tip and "ears". The actual voltage will be constantly changing since it's music. It's actually easier to see on an old analog VOM than on a digital.

When the RCA's are plugged in and the amp gains set up a bit, you'll also see AC signal at the speaker terminals if it's working.
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