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Amp cutting off


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4 replies to this topic

#1 of 5 OFFLINE   Juan Castillo

Juan Castillo

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Posted March 02 2004 - 06:17 AM

Alright guys, I need some input. Here's what I have :

Cerwin Vega 12" 8ohm DVC sub from an old SW12B home sub. I built a sealed 1^3ft box and wired it in parallel for a 4ohm load.
This sub is powered by a kicker KX120.2 amp, bridged to put out 120 watts at 4ohms.

I know the sub sucks, and the amp is not a power house, but for me and my budget, its ample.

Heres my problem. When playing super bass heavy music, the sub sound great, and doesn't distort, but the amp will cut off, when I turn it down, it comes back on.

I likely have a bad ground, since I re-installed the rear bench before grounding and took the easy road by grounding on top of the bench mounting plate and using the nut to tighten down on the ring terminal. I didn't even bother to scrape paint..

Knowing this, I can easily fix the "problem" but I am not sure this is the "problem". Can a weak ground cause the amp to cut off at peak power? Or is my sub doing something funky? Like I said, it is not distorting at all, actually it is sounding its best when this happens.

I am using a 10 gauge power lead, fused at the battery with the same amp size fuse as the amp uses. Would a heavier gauge make this go away.

More notes on install..

Chevy Silverado ext. cab LS trim
factory radio, using line level inputs on amp.

Opinions please?

#2 of 5 OFFLINE   Brad_Harper

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Posted March 02 2004 - 06:49 AM

Next time the amp cuts out check to see if the protection circuit in the amp has tripped. There is probably some lights on the amp itself to indicate this. If it is tripping your amp is probably defective. I would fix the ground regardless. Don't forget in vehicles current flows from the ground to the battery.

Also your line level convertor may be overloading the amps inputs at high volumes. Adjust the gain on the line level convertor if possible. Otherwise I am out of ideas.

#3 of 5 OFFLINE   Juan Castillo

Juan Castillo

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Posted March 02 2004 - 06:57 AM

What factors other than a defective amp, can cause it to trip?, and I am not using an LOC, just the high level inputs direct from rear speaker channels, which, could possibly be the problem? If I turn it up, can the amp handle the extra line voltage the speakers put out?

#4 of 5 OFFLINE   Brad_Harper

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Posted March 03 2004 - 02:06 AM

If you are using the LOC of the amp itself then that shouldn't be the problem. Overheating, short circuited speaker wires, and low current draw can all cause the amp to malfunction. There could be a problem with your woofer coil in that when it heats up something inside of it shorts out.

#5 of 5 OFFLINE   Matt Hobbes

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Posted March 26 2004 - 01:36 PM

WARNING:
this is long and might have rant-like qualitiesPosted Image

I doubt you have the same problem (though it prob is a loose connection somewhere), but maybe it will help somebody whose amps seem to always cut off at loud volumes and/or cut out after only being on a short period of time...
If you want to skip to what I found to be the problem, scroll to the red text.

I was a newbie at car audio, didn't know what gain meant on an amp, so I figured if I spent a decent amount of money on speakers/amps at a reputable shop and I'd have a pretty good first system.

Shortly after it was installed, I was having problems with both of my amps, one for the sub, one for the surrounds, cutting off/getting extremely hot after only playing a short amount of time (rather loudly was about 20 min)... if the volume was lower, it would last slightly longer but usually one amp would cut out around the 60 min mark.

This was right after a brand new install, so I took it back to the shop, which was supposedly the best shop in the area (Gainesville), and they found nothing wrong. I went to various audio forums around the net looking for answers; most suggested checking the ground as the culprit. I took it back to the shop, and they looked again, again found nothing and told me two things: needed a better amp, and that playing music loudly for longer than 30-40min will cause most amps to shut off/overheat.

Well this didn't make much sense from what I'd read on forums, and people that I knew with systems were usually cranking them and never had overheat problems. But being new to the car audio world, I figure I'd take the shops' advice: that my equip wasn't good enough, buy better stuff and to limit playing music loudly. Neither solved the problem. I tried to get them to look at my car a third time, but they became rude and said I was playing my system irresponsibly and it wasn't their problem... Oh yeah, my sub and my right front speaker ended up blowing during this time period.

Unfortunately, being in the military, I had to move to California, with my stereo problem unresolved.

I ended up taking my car to a couple other shops (circuit city and car toys and 1 local shop) to try and fix the problems... the sub had been replaced but the front speaker was still blown, and the problems with the amps remained.
Not one of the three shops had found a problem... all of their solutions was new equipment...

This was roughly six months after the inital install, so I was sick and tired of the "games". So I did lot of research and found someone at work (who did custom installs) to help me take a look at the system.

We found out that when the orig shop installed the the amp board on the back of the box, that it was mounted too far down partially obscurring the top input for the sub, causing a really loose line in connection. Moved the amp board up, pushed the loose input all the way in, tested the system: the sub now put out twice its previous volume! Also found out the reason the front speaker blew was that the high pass filter was turned off... had a 5.25 speaker receiving a full range signal (had the hpf off on the HU since the amp's were supposed to be covering them). We also noticed small things like the HU was extremely difficult to remove because they had left no slack in the wires, and some of the install work on the front door seakers was rather crappy once you removed the door panels. The ground, though, was fine.

After this, my system had no problems with volume or heat. It just cost me too much money (+1500), time and frustration. It has also made me wary of all shops... they seem only to be interested in profits, and would outright lie to my face (telling me pioneer premiers were crappy, or trying to sell me "the best sub" made by diamond, which turned out to be its lowest end model, or that most amps shouldn't be played at loud volumes over 30-40min or they will overheat) I'm really not sure what the shops, especially the orig one were doing when I brought my car in to diagnose the problems.

One plus side I guess is that I now know what to look for, and that I learned a lot about audio. Hopefully you'll have much better luck than I didPosted Image

Any loose connection/ground could cause your amps to overheat. Amps should not cutoff after short periods of time even at loud volumes if installed properly and are matched to the components. 10 guage wire should be fine.

equip:
-Premier DEH-P630 HU
-earthquake 5.25" and 1" tweeters (orig pioneer premier fronts, but the right one blew)
-pioneer premier rear:6.5"
-powered by 250W mtx 2150 (only 5.25 and tweeters now)
-diamond 12" CM3 12D4
-powered by jl 250.1 amp (had a rokford fosgate which was the one that blew, kicker comp vr (too boomy: this was the 1st audio shop's idea of fixing the sub problem -orig powered by an eclipse amp which also blew) and then the matching jl for the current amp, but it bottomed out on low bass at high volumes)
4 guage wire


-I probably had as much money on blown equipment as in the final config... I did get some of it back... not enough though
hobbes