Printer Friendly Forum Posts - Defective HU or Amp?

Hello,having some trouble with my stereo. 2005 durango with basic hu feeding an infinity 5760a 6ch amp, hooked up to polk speakers in the doors and a box in the back. when i turn the radio up past 10 or 11(goes up to 38 on the dial) the amp will cut out, and slowly come back on, but if i keep it at that level it immediately shuts down again so i have to turn volume down to 5 or 6. this will happen even if i have had the car off all night and have just powered the amp so it is not a matter of overheating. looking for opinions, defective amp or hu? amp is about 1-1/2 years old and again hu is the basic hu from dodge(didn't want anybody trying to steal anything). thanks for any help you can give me.

Allen

allencass wrote:

the amp will cut out, and slowly come back on, but if i keep it at that level it immediately shuts down again so i have to turn volume down to 5 or 6.

What do you mean by 'slowly coming back on'?

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"I'm finished!" - Daniel Plainview

after about 3-5 seconds, the volume will slowly start to rise to whatever level i have it set on.

but as soon as it returns to that volume it cuts back out again?

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"I'm finished!" - Daniel Plainview

it cuts out again if i have the volume up at the 10-12 range. if i turn it down, it will normally stay on. it usually happens when bass is supposed to hit, but if i put on talk radio it seems a little better.

I've had this problem before. It turned out I had a bad ground to the amplifier. Check your ground on the amp and make sure you have a clean metal to metal contact.

checked ground already but it can't hurt to try again and rescrape some metal.

Could be gain is way too high on the amp, or the impedance of the speaker/subs could be too low for it to handle. Or possibly a short in the speaker wires, or possibly a speaker. You said if there is a bassy song it will cut out, whell you could have a shorted out voice coil. There is sooooooooooooooooo many possibilitys, its just a matter of hours of trial and error.

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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.

Yea, Alpine Guy is right here...

Basically, somewhere in your output stage you're shorting out somewhere.. perhaps a Voice Coil is shorting at excursion and that is why that specfic volume level is giving u trouble.

First step:

Disconnect speakers one at a time and see if the other three will play at that level w/o reproducing that problem... if it does.. you found your shorting speaker...

Prolly not a short in the speaker wire tho, that would prevent the amp from playing at all..

Try a new ground, try checking each speaker by process of elimination.. post back with results eh?

Did this problem just start or has it been this way since installation?

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"I'm finished!" - Daniel Plainview

will try the suggestions, just started happening, system installed for about 6 months. will post back with results

Well my ground problem was on initial install. Now I'm leaning more towards a bad voice coil shorting out.............. So many things to check. Good luck!!!

All great advice.

How is your amp getting signal, are you using high quality line out converters, or are you using the high level inputs built into the amp (assuming it has them)? If you're using high level inputs, I'd recommend using a line output converter instead- using high level inputs can sometimes also give the symptoms you are describing.

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My ex once told me I have a perfect face for radio.

OK, tried both subs hooked up again,same problem, disconnected both and tried each channel separately, seems that by themselves there is no problem, even when the amp is bridged. so the only time there seems to be an issue is when both subs are hooked up at the same time. I am using high level inputs as the stock hu has no preamps. will probably upgrade the stereo soon, we'll see. any more input on the problem?

It sounds like when you're running both subs, you're hooking them up bridged parallel (both positives of the subs to the positive terminal on the amp, both negatives together)- which is probably too low an impedance on that amp. I recommend using a mono block class d amp to run your subs.

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My ex once told me I have a perfect face for radio.

When I bridged the amp I only used 1 sub. when i am using both subs i am not bridging the amp at all. not sure if that tells you anything else. here is the link for the owner's manual,not sure if you can tell anything from this but if you check the last page it has the specs, again i have the 5760a:

https://manuals.harman.com/INF/CAR/Owner%27s%20Manual/REF%20AMP%20OM%20FINAL%20rev%203-15-04.pdf

OK,not sure if anyone can give me any further input, when powering each sub individually,no problems. even with the amp bridged. as soon as i try to power both subs, whether or not the amp is bridged it results in the first problem i discussed.any input?

would wiring in series or parallel make any difference? I have a remaining warranty on the subs, so i can get it fixed if that is the issue but before i do that i want to make sure that is the problem.

OK, not sure if this means anything but I have the amp bridged, wired in series, no cut outs so far after running for about 15 minutes or so. BTW the subs are SVC if that makes any difference

Last time, hoping for some input. Worked fine wired in series no cutouts with amp bridged, when trying parallel bridged, it started cutting out again. So, i'm not sure what the prob may be still. bridged to one sub or the other, no prob. bridged wired in series both subs, no prob. unbridged to one sub or the other no prob. wired in parallel, problems. both subs hooked up not bridged, problems. bridged to both subs, problems. any answers?

allencass wrote:

Last time, hoping for some input. Worked fine wired in series no cutouts with amp bridged, when trying parallel bridged, it started cutting out again. So, i'm not sure what the prob may be still. bridged to one sub or the other, no prob. bridged wired in series both subs, no prob. unbridged to one sub or the other no prob. wired in parallel, problems. both subs hooked up not bridged, problems. bridged to both subs, problems. any answers?

This indicates your amplifier simply cannot handle the impedance load of your speakers in parallel. I believe this was already mentioned to you?

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i had this installed in another vehicle with no problems. could it be something else? am i just an idiot or what?

geepherder wrote:

All great advice.
How is your amp getting signal, are you using high quality line out converters, or are you using the high level inputs built into the amp (assuming it has them)? If you're using high level inputs, I'd recommend using a line output converter instead- using high level inputs can sometimes also give the symptoms you are describing.

oh,yeah. when i had it in the other vehicle the hu was an aftermarket with three sets of preamps, could this be the whole problem?

That makes a huge difference, indeed. I bet you didn't adjust any of the controls on the amp when you transplanted the gear into your current vehicle, right? Do a search (upper right hand of the screen) in here on setting gain, and read up. Also, I'm not a huge fan of using an amp's high level inputs. You're much better off using a good line-out converter, which will give you rca outputs.

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My ex once told me I have a perfect face for radio.

I have adjusted the controls, I will read up on gain, and l will probably get an aftermarket stereo soon, will check out crutchfield for research on HUs with three preamps