Audio Systems: Amp not working, impedance load, ohm load

Question
QUESTION: I have two solo baric L5s ran in parrellel in a ported box, JBL GTO 1201.1 amp, 2 gauge power and ground wires, i installed everything about a month ago and it has been working fine ever since, but today i was in the car and the subs just cut off, i got home and the protect light was on on the amp, now it doesn't even come on, what is wrong?

ANSWER: Check the fuses first to see if they are out (there could be as many as three of them, depending on how you run the 12v lines.)

Check the impedance of the speakers; if they are wired in parallel your impedance loading to the amp is 1/2 that of each speaker. Then check the impedance rating of the amp; if the impedance load is lower than the rating of the amp that could be the problem.  (Overheating, for example).

Amp could have failed for no reason or from excessive overdrive if you have been running them at full power (and the amp is not ventilated properly or a hot day and it just got too hot).

If you know the amp has power and yet the lamp is still not on their may be a fusable link inside the amp that has opened up. If so, it is likely the amp is fried or has lost its output stages for some reason.

The amp does not like less than a 4 ohm load; or in bridge mode a 3 ohm load is rated okey (although I shudder whenever I see loads so low, even with this rather excellent class D amp).

Also, check to make sure the woofers are not accidentally putting a short on the speaker line.

Hope this helps.  Let me know more if you need.
Cleggsan


---------- FOLLOW-UP ----------

QUESTION: i think that amp is stable at 1 ohm, thats how i have it set up, with a 1 ohm load, all fuses and everything are fine i checked all of that before i came in the house, i unhooked the speaker wires and it still wont cut on, so i guess the amp is fried then, gotta spend another $500 on a amp i guess

Answer
No.  Take it to a good audio shop and they may be able to fix it for cheap. It is a class D amp and not everyone knows how to troubleshoot them, so carefully call a couple of shops asking if they know how to work on class d amps.  There are some easy repair tricks if just one component goes bad it shuts down the whole affair, but a simple replacement can make it go again.  For example if the switching clock is down it may be a repair of less than $50.  If the output switchers (probably FETs) need replacing it is still not terrible for cost.

But, once more, check to make sure the amp has live 12v.  If you don't have a vom, get the little $9.83 meter at Walmart and check the power lines. I have seen fuses that look good and even measure good with an ohmmeter; but with high current they go open.  

So, give it another whirl before caving in.

Cleggsan