My JBL bp1200.1 is acting strange...HELP!!!


Unregistered guest

i used to have a kx600.1 amp w/ 4 ga wiring, 180A alt, and a 2 farad cap in my car. i had a 60A fuse 1 ft from the batt, but recently i bought a jbl bp1200.1 and another solobaric 12" dvc 4ohm.

i hooked both subs to the 1200.1 (1 ohm ) and just hooked the 1200.1 to the same wire i had the 600.1 on. it sounds good, but its doing something strange.

no matter how hard i drive the amp i can't pop that 60A fuse at my batt., what up w/ that???
does this mean that the bp1200.1 is drawing less than 60A from my electrical system???

if so then it must only be putting out ~700watt and not 1200w like the amp should, because the amp should draw 114A, right? surely if the amp draws 114A it should pop that 60A fuse....RIGHT????

i mean, my batt. gauge doesnt drop and the lites dont dim, so the alt is giving my electrical system all the juice it needs, right???

why is this 60A fuse still holding up???

Bronze Member
Username: Carguy

Post Number: 27
Registered: Nov-04
Hey wtf, that jbl amp is 1200w at 2/1 ohms. I'm not sure if it's a class D or not but if it is, it'll draw less current than class AB. Also, if you're 60A is not blowing, then you're not really driving the amp to the max. Maybe even with the volume up, your amp could be delivering only 60% - 80% of it's power. Did you set the line input level from the HU to the amp correctly? If it's set too low, the amp might not be getting enough voltage. From playing with my amp, that's what I found out. I had one that said 500W but only put out 250W cause the level was set too low.

Hope that helps.

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5440
Registered: Dec-03
114A is at full output. that's be volume at absolute max with a test tone that put out pink noise at peak level generally.
every time you double your volume in the car, you're using about ten times the power to do it, so with this in mind, and most people never turning their system up all the way if for no other reason than to avoid clipping and distortion, you never really hit the full power of the amplifier.
It's quite possible that you really aren't going over 60A of *constant* current draw, and a fuse is rated to withstand an ocer-current of a certain percentage for a specific amount of time before burning.

"Fuse Opening Time:
A fuse does not blow when the current reaches its rated current. It is designed to pass its rated current without opening. A fuse will take varying times to blow under different conditions. A fuse will pass significantly more than its rated current for a very short time. It may take 10 minutes or more to blow a fuse at 25% over its rated current. The table below is an example of the specifications for a slow blow fuse. You can see that a 20 amp fuse may pass 40 amps of current for as long as 5 minutes before blowing although it probably wouldn't take a full 5 minutes to blow. The times for other fuses will be slightly different."

example for an ANL type fuse:
110% @ 4 hours min
135% @ 1 hour max
200% @ 5 minutes max

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5441
Registered: Dec-03
"that jbl amp is 1200w at 2/1 ohms. I'm not sure if it's a class D or not but if it is, it'll draw less current than class AB."

It is class D with a regulated output stage @ 1 ohm. JBL's specs list peak current draw as 114A.

"I had one that said 500W but only put out 250W cause the level was set too low."

just for the record, gain, or input sensitivity doesn't affect the actual power the amplifier puts out, but it will affect how the system sounds. underdriving the input stage of an amplifier just causes the amplifier to amplifier a very weak source signal, much as overdriving the input stage can cause clipping. gain is really just a means to balance input stage of the amp to source line voltage since several factors can have effect on that final voltage level.
for what it's worth.

Unregistered guest
so should i keep the 60A fuse in or change to a 120A?

also, should i put a fuse between the cap and the amp?

Bronze Member
Username: Carguy

Post Number: 35
Registered: Nov-04
I'd keep using 60A fuse if it's not blowing. You don't need a fuse between the amp and the cap, the one near the battery is good enough.

Silver Member
Username: Joe718

Brooklyn, NY

Post Number: 185
Registered: May-04
well actually the fuse at your batter is supposed to equal your system amperage draw. So if you have a 60 upfront and i know that amp itself has 3 40amp fuses built into it. that 60 will pop eventually. So what you should do add up your all the fuse ratings on your amps crossover etc and put a high current anl fuse up front and as you get to your amps get a distribution block that way you can break down exactly how much current goes to each amp.
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