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Author Thread: Why is my amp cutting off??
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New member
Username: Gball6

Charleston, IL

Post Number: 10
Registered: Dec-04
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I have a JBL BP1200.1 amp hooked to 4 Audiobahn speakers (400 RMS) at 2 ohms. Sometimes the bass cuts out while a song is playing. I checked the amp and its not hot, so I don't know what the problem is. Help please
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gain=high?
Unregistered guest
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how high is your gain set????
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Bronze Member
Username: Gball6

Charleston, IL

Post Number: 11
Registered: Dec-04
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What is a gain?? What does it effect? I also noticed that my car rides alot more sluggish when I have my sounds up, can i be draining to much power? I have a bass cap (1.0 Farad), but at night my lights still dim. But my amp cutting off is my main concern
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Gold Member
Username: Carguy

Post Number: 1807
Registered: Nov-04
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Garry, you have an amp that's power hungry. The gain/level control is used to match the amp's input sensitivity to HU's preout voltage. Most HUs are 4v. So set that control to 4v. Incorrectly set gain/level will damage your amp, as well as your sub.
As for your car, that amp is killing it. DO NOT operate the car under your current state. Sooner or later, your electrical system/alternator/battery will die. It'll cost you tons of money in repair cost.
Invest on a HO alternator. Get one around 200A. For your capacitor, it's 1F per 1000w. So you should've had 1.5F - 2F cap.
Check out 4alterstart.com.
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Bronze Member
Username: Gball6

Charleston, IL

Post Number: 12
Registered: Dec-04
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Is there any alternative to getting a HO alternator. I have seen people with numerous bass caps and even extra batteries. Is this something else that i can do or is a HO alternator my only solution?
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Bronze Member
Username: Gball6

Charleston, IL

Post Number: 13
Registered: Dec-04
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Is there any alternative to getting a HO alternator. I have seen people with numerous bass caps and even extra batteries. Is this something else that i can do or is a HO alternator my only solution?
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Gold Member
Username: Invain

Michigan
United States

Post Number: 1526
Registered: Aug-04
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Only thing that will fix it correctly is an alternator.
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Silver Member
Username: Fishy

Tamarac, FL
USA

Post Number: 611
Registered: Sep-04
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Extra batteries and caps only put more stress on your current alternator. If the alternator is the root of your problems you may find yourself driving down the road one night w/o headlights and if you don't have AAA thats when the fun really begins.

If you could find out how many amp alternator you have that might help diagnose the problem.

-Fishy
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Bronze Member
Username: Gball6

Charleston, IL

Post Number: 14
Registered: Dec-04
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My alternator is 105 amps. I went to a sound shop today and they told me that my amp was cutting off because its not getting enough power at times and its going into protection. The guy at the shop said that i should invest in a larger battery so that the amp can get continuos 12 volts. I also went to a alternator/battery specialist and i had them hook up my alternator and battery while my sounds were playing at max and he said that there was no major difference in the voltage. Any suggestions
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Silver Member
Username: Fishy

Tamarac, FL
USA

Post Number: 629
Registered: Sep-04
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Did that specialist happen to mention what that voltage was? If it was say between 13 and 14 volts your alternator may be keeping up just fine and there may be some other problem. I hate to say this but "the guy at the shop" doesn't seem to know what he's talking about. Altho having a bigger battery will help out if you like to run your system with the engine off it also puts a heavier load on your alternator when charging the thing. When your vehicle is running you get ALL your power from the alternator, at least until the voltage falls below that of the battery. Your battery takes over at that point and thats when you start to run into problems.

Regardless, thats a big amp, and if you're truly pushing 1200 watts its probably capable of drawing 100 amps(whats the fuse rating?) and that doesn't leave much power for your headlights, a/c, etc. as well as the REALLY important stuff like your mids/highs amp. :P

A HO alternator is probably a good investment. Altho it may not solve your problem a bigger battery or cap definitely won't.

-Fishy
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Gold Member
Username: Carguy

Post Number: 1854
Registered: Nov-04
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Sounds like those shop guys have other motives in mind. If your alternator/battery/electrical system dies, the make money.
Getting a larger battery is a "cheap, non experienced and I have no idea what I'm talking about" guy's solution to the problem. Don't listen to them.
The only way a 2nd battery will help is with proper installation using isolators like Orion MBR 70. It still won't solve your alternator problem though.
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