switched hu, sound cuts with volume jump

I just changed my head unit from an older pioneer to the new avhp4300dvd. The existing system has a 5 channel audition amp powering just door speakers (four) which had no issues with the old head unit. New system has a 12v relay bypassing the parking brake lock (copied from the YouTube "soundman" video on the pioneer bypass).

Everything works, except if I turn the volume up above quiet levels (approx. Level ten). At this point it will promptly cut the sound, but the unit goes about it's business thinking it still works. If I turn off the car and reboot it will once again work unless I turn the volume up again. It does this for each source, DVD, cd, radio, etc. at the same approximate volume.

Is there some sort of setting I am screwing up? Did I wire something wrong? Thanks for any help you can offer!

2004 Subaru sti with pioneer avh-p4300dvd and audison lrx5 amp and some focal door speakers of some sort, upgraded from older pioner premiere head unit.

sounds like your amp is going into protect, did you reset the gain on the amp when you installed the new HU. a higher voltage output could be causing the amp to trip. either than or you pinched the rcas when you installed the deck.

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Chances are I have the preamplifier settings wrong, I will look into that right now and check what they are and try to find out what they should be. Also, could you please explain the RCA comment? As in they are bent funny behind the unit?

The previous pioneer hu had 6.5v preouts and the new unit has 4v. I have looked at the audison lrx 5 600 manual and don't see anything I can adjust to set what voltage it would be expecting. I see some "level adjustment" turn screws and tried to set them to 4 but the problem persisted. I don't have the subwoofer hooked up, does that have something to do with this? Perhaps I installed an extra fuse resistor on the yellow or red lines, could that cause this?

Ok I removed the unit, removed the double fuse resistor on the yellow and red lines, checked the RCA cables and they were ok, and turned down the input sensitivity/output level knobs on the amp to minimum. I then turned up the volume and got it to 25 before it cut out but it still set off the safety on the amp. No other wiring or anything changed so I am at a loss. I also noticed that with the ignition in position 2 I get a high pitched whine from the alternator, but I am not sure if that is news or not.

I really appreciate any help or advice you can give.

The alternator whine might simply be its regulator. (EG - assuming IGN on but engine not started/running....)

I think you are right, I am at a loss.

Hey, just a hunch but does your amp have a preamp/high level input switch? If so, is it set to preamp? From what you've explained, it sounds like your amp's getting too strong of a signal or it has a bad ground.

with no knowledge of any messing with the amp other than minor adjustments, I can't see how a bad ground would have happened but it's worth checking. Amps will cutout if they don't receive the proper amount of power to include having a poor connection.

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Nick C.

as far as the rca's, they could be pinched anywhere down the line and still give you the same results. also the can look fine but still be bad on the inside. if you can, run a new set of rcas between the new radio and the amp. just run them through the car to the amp just as a temporary test and see if the amp still cuts out.

my reasoning for this is mainly because you said that all you changed was the radio and didnt do anything to the amp or speakers and that everything worked fine before. so other than a freak accident where something happened inside the amp or damaged a speaker, the problem has to be something before the amp. is there anything between the amp? like a crossover or EQ?

also, the stated voltage of an rca output doesnt really mean that much. its similar to the "max power" rating on an amp. so if you didnt reset the gains on the amp to match the new radio then it could have been enough to hurt the speakers a little bit especially if the speakers are sensitive to abuse. so this is also a possibility.

take all of the speakers loose from the amp and test them for a bad ohm load. then turn the volume up to where it would usually cut out and see if it still does it with no speakers on the amp.if it doesnt cut off then start putting the speakers back on the amp one at a time and see if it still cuts off.

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Good ideas. I will disconnect the speakers and check them individually to see if one of them is damaged. If when all the speakers are disconnected I get the protect then it can't be the speakers. I wonder if my ground is overloaded or something, but I thought that protect mode was only pertinent to what was coming out of the amp and for the speakers and wouldn't protect if it was an input that was set wrong? Could some of the rcas or speaker wires come loose and shorted out or something and ruined the amp or speakers or is that not really an issue? If that were the case wouldn't it not work at all than just not work at high volume? I believe focal speakers and most car speakers are four ohm so I will try to figure out how to test the ohms.

There is no low gain / high gain switch on the audison lrx5.600, just a set of turn dials from two to twelve that set the "input sensitivity" which I tried at the lowest setting of two with only slightly better results, louder volume but flat and dull sounding and still not loud enough for freeway driving. Thanks again, will attempt your suggestions and follow up.

Ok I followed your advice and checked the system from the ground up (haha...) anyway, I disconnected inputs and speakers and everything was fine up to max volume. I then began adding speakers one by one and testing to high volume, still ok.

Interestingly what I found doing this was very strange. The two back speakers are fine, but in the front it gets weird. The front has a tweeter/woofer presumably with a passive crossover in the door. When I hooked up the right front set of lines to the right front output on the amp I got full sound in the driver and passenger front of the car...when I hooked up the last set of cables nothing changed, except the amp went into protect! Then I tried taking the bad set off, and putting the good cables into the left front output this time...same thing, sound out of both speakers up to full volume, and would go into protect if the "bad set" were plugged into the right front output.

I am even more perplexed now because the install looked professional from what I could tell and I guess I didn't have the car long enough to be able to tell that the front left and right speakers were both playing only a single side of the stereo signal. Is there a reason for this? Is this a common wiring mistake, and where would be the best place to fix it? I can't find forum history that matches this scenario. Thanks!

I should add, if the final set of speaker wire were plugged in it wouldn't go into protect right away, and it wouldn't change the audio, it would go into protect over a medium volume threshold as before.

hmm. that is pretty strange. probably what happened was a speaker wire got pinched in the past and someone was really really lazy. so instead of running a new wire they just connected the left and right side to the same wire. they probably left the other wire hanging and during the install of your new radio it somehow came in contact with ground or something else.

so, i would take the opportunity to just do it right and run a fresh set of wires for your front speakers. problem should be solved

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Cool. Thanks again for the help, without it I would have screwed something up! Thought you guys would find the end result pretty unusual and funny.

Yes, I agree check or replace the wires to the front speakers for the latest problem.  The orginal problem could also occur if the unused speaker connections from the new radio are shorting out when you mount the radio.  Good luck!