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my sub and amp work perfectly when my car is turned off but when i start it my sub goes quiet and dies,does anybody know what my problem is,

im running a legacy 2000watt amp and a 15 inch in phase sub,

its a mercedes 200,im running a 2000 watt legacy amp and a 15inch sub,it works fine when the car is turned off,everything great,but if i start the car the sub works at low volume but when i turn the vollume up the sub dies(the protector l;ight opn the amp comes on,,even with everything else in the car turned off,i have tried it with the car running and the amp powered by a totally seperate battery and it works then

ok,just took a look at it and it only has this problem on the one channel,the other channel works fine,its a two channel anp and i only use one channel,

Can you not bridge that amp (run both channels to one sub)? Maybe the amp doesn't like you running one channel at a time...I dunno, that's just a guess...

Make sure everything is hooked up properly.. also make sure you have a solid ground...

I suspect, you had the amp bridged running the sub... amp pulls big power, and cutts out because of voltage drop, due to a bad ground..

running one channel, the amp is putting out much less power and everything is OK...

what is the impedance of the sub ? (what ohm?)

i have a solid ground all the wiring is fine,its got two channels they both work when the car iss of but when i start the car the car the one side will work fine but if im pluged into the othe channel it dies and cuts out,i have not bridged it

I dunno, the only time I had a sub cut out on me like that, it was due to faulty wiring...

If you have a volt meter measure the voltage at the batery terminals with the car off, then again with the car on. Repeat at the amplifier.

What are your results?

It could be that your alternator is faulty and having problems keeping up with recharging the battery and running the system.