Amp problem !?

[Wingman21]

Hey guys,
yesterday while I was driving back from work, my SUB just stopped working suddently. So when I got home, I checked in my trunk and the amp was cold and the red light wasnt on. Could it be that my amp just died on me or its just a fuse problem !? Is the fuse under hood only for the amp or also for the HeadUnit because my HU is still working fine, its just the amp that isnt turning on (dunno) !? I did try to check it, but I can get the freaking plastic cover open... anybody knows how to open it :) !?

Thanks

[Tommy1005]

the fuse next to the battery is specifically for the amp......I would start there. I can't remember if this amp has a fuse actually on the amp or not, if it does that would be the second place to look. The plastic cover has a little clip on one side, it should just pull open farely easily. I have taken all the factory wires out of my car except the remote wire since I replaced all the subs, amps, and speakers. If I were still running the stock amp, I would be tempted to buy an amp wiring kit and rewire the power and ground wires.

[jersey_emt]

Yup check the fuse under the hood, as well as the one on the amp

[Wingman21]

Just checked the fuse under the hood during my lunch time and it is blown so that must be my problem (cool) !!! What could has cause that ? Could the cold weather here in Quebec has made the cold sub pump more juice from the ampli (dunno) !?
Anyway, Im gonna change it tonight and see if it happens again. If so, Im gonna start checking for touching wires on my SUB :) !!!

Thanks

[1sty]

You may have been cranking on it too hard, causing the amp to distort and becuase of that, draw to much power.

Other then that, there might be a frey in the wire somewhere. If any part of it touches any grounded metal in the car, the fuse will and should blow.

EIther way, it did its job and gave its life so that the music could go on :D

If the speaker wires on the sub were loose or touching the fuse on the amp would blow. Not the one under the hood.

[Tommy1005]

I would also recommend replacing it with a 30 amp fuse, instead of the stock 20 amp fuse........a little extra protection never hurt anybody.

[Wingman21]

I would also recommend replacing it with a 30 amp fuse, instead of the stock 20 amp fuse........a little extra protection never hurt anybody.
Its not a 20amp but a 15amp stock !!! And for extra protection shouldnt I lower the fuse amp instead of raising it ;) !!!

[Tommy1005]

And for extra protection shouldnt I lower the fuse amp instead of raising it ;) !!!
I really hope that was a joke......I've been up since 6 this morning, so please forgive my lack of sense of humor if it was.

[1sty]

Its not a 20amp but a 15amp stock !!! And for extra protection shouldnt I lower the fuse amp instead of raising it ;) !!!Your absolutely correct. You want the fuse the lowest amount possible above the amperage the amplifier itself can cleanly draw. Anything higher will allow the amp to distort more and would not blow as quickly if the power wire shorts out. The amplifier might be capable of drawing more then 15 amps at the very extream. That is assuming a 60% effeciency rate (being really generous) and a 150 watt max draw with the factory 8 ohm subwoofer. Being 60% effeiciet the amp may actualy draw 250 watts to make 150. In this instance at 14.4 volts or what is likely to be a little lower, the amp could draw over 17 amps. Again, these numbers are ALL estimations as none of these stats are published by kenwood. Those being max power at 14.4 ats @ 8 ohms or effeciency when bridged to an 8 ohm load.

All that being said, going from a 15 amp to a 20 amp fuse isn't risking much. Any short in the power wire will blow each fuse extreamly quickly.

[Wingman21]

I really hope that was a joke......I've been up since 6 this morning, so please forgive my lack of sense of humor if it was.
(dunno) !!! If you raise the fuse amp (15->30) it means more current getting to the amp before it blows so thats less protection in my own book !!!!!!!!!!!

[Wingman21]

Your absolutely correct. You want the fuse the lowest amount possible above the amperage the amplifier itself can cleanly draw. Anything higher will allow the amp to distort more and would not blow as quickly if the power wire shorts out. The amplifier might be capable of drawing more then 15 amps at the very extream. That is assuming a 60% effeciency rate (being really generous) and a 150 watt max draw with the factory 8 ohm subwoofer. Being 60% effeiciet the amp may actualy draw 250 watts to make 150. In this instance at 14.4 volts or what is likely to be a little lower, the amp could draw over 17 amps. Again, these numbers are ALL estimations as none of these stats are published by kenwood. Those being max power at 14.4 ats @ 8 ohms or effeciency when bridged to an 8 ohm load.

All that being said, going from a 15 amp to a 20 amp fuse isn't risking much. Any short in the power wire will blow each fuse extreamly quickly.
Thanks for the good explanation. I might raise my fuse in the futur to 20amp, but first Im gonna check if the stock one (15amp) blows again !!! Might be the cold weather here in Quebec that make the sub draws more current to move itself (dunno) !!!

[1sty]

Might be the cold weather here in Quebec that make the sub draws more current to move itself (dunno) !!!
Nope, it doesn't work like that.
CHeck the sub with a DMM if yo have one to be sure its in good health. If it si damages it may be showing a lower resistacne then it should. This would casue the amp to pull more power from the battery

[Wingman21]

Nope, it doesn't work like that.
CHeck the sub with a DMM if yo have one to be sure its in good health. If it si damages it may be showing a lower resistacne then it should. This would casue the amp to pull more power from the battery
Ok... By the way, I dont have the stock sub anymore I got a new one under warranty. Its a 400w Cerwin Vega. Can it be drawing more current or its the amp power that determine that (dunno) !!! Sorry but Im not an expert when it comes to audio :) !!!

Thanks

[jurgs01]

Ok... By the way, I dont have the stock sub anymore I got a new one under warranty. Its a 400w Cerwin Vega. Can it be drawing more current or its the amp power that determine that (dunno) !!! Sorry but Im not an expert when it comes to audio :) !!!

Thanks
How do you have it wired? A bigger sub can max out the amp and draw enough current to overheat it. If this is happening I would get a bigger amp (you will need to up the fuse, but check with the amp manual to see what type of power it will put out to the ohm rating of your sub). If it is putting out a max of x watts, then divide that by 12V and divide it by 0.6 to get the correct fuse.

[Wingman21]

How do you have it wired? A bigger sub can max out the amp and draw enough current to overheat it. If this is happening I would get a bigger amp (you will need to up the fuse, but check with the amp manual to see what type of power it will put out to the ohm rating of your sub). If it is putting out a max of x watts, then divide that by 12V and divide it by 0.6 to get the correct fuse.
Well, must be wired just like the stock one because my dealer installed it !!! I think its a 4ohm compare to 8ohm for the stock one... so if the resistance is lower it means more current right ? How can I know if the stock amp is enough for the new sub ?

Thanks

[1sty]

Well, must be wired just like the stock one because my dealer installed it !!! I think its a 4ohm compare to 8ohm for the stock one... so if the resistance is lower it means more current right ? How can I know if the stock amp is enough for the new sub ?

Thanks
Did the dealership buy the new sub?
Odd that they'd buy a cerwin vega sub.

Being a 4 ohm sub, it will force the amplifier to draw theoreticly twice the amperage that the other sub did. Realisticly it will cause it to draw about 50% more. This is definitly a reason that the amp might be blowing its fuse.

Which amp do you have?
The MSP had 2 diffent ones. The KAC-5201 is only rated for a 15 amp fuse so it should be fine regardless. The older amplifier, the KAC-529 was a little less effecient so that would be a little more likely to pop a fuse.

What is the model number of the new sub?
Keep in mind that suboofers handle power, they do not create it. So a 400 watt subwoofer (although ususaly a major exageration expecialy for an 8") means that it can handle up to 400 watts. Be that power rms, peak, or imaginary I wouldn't know until you tell me the model number of it.

[Tommy1005]

it's a 150 watt RMS sub.....or atleast that's the only 8" Cerwin Vega that I can find. It can however be had as a single or dual voice-coil woofer. If it is a dual voice-coil woofer, it could be straining the amp, causing it to draw more power, thus popping the fuse. I would try a 20 amp fuse, if it pops, then I would try a 30 amp fuse. If it pops, then you need to upgrade the amp, and along with that, it would be a good idea to upgrade the wiring as well. I'm a big fan of using the biggest wiring possible to transmit the largest amount of current possible, and upgrade to a real fuse under the hood instead of the cheap fuse we currently have.

[jurgs01]

If the 30 Amp fuse pops you amp is pushing 360 watts (30 amps @ 12V). Maybe a little more because the battery usually sits around 14+. That's way more than the amp is rated, and the amp shouldn't be pushing it's limit a lot anyway. The amp fuse would probably give before that point.

[1sty]

If the 30 Amp fuse pops you amp is pushing 360 watts (30 amps @ 12V). Maybe a little more because the battery usually sits around 14+. That's way more than the amp is rated, and the amp shouldn't be pushing it's limit a lot anyway. The amp fuse would probably give before that point.
Its not as straight forward as that. If the amp is capable of a 60% effeciency, then to produce 360 watts it has to draw 504 watts from the battery. Even at 14.4 volts which no battery can really maintain once the sub starts moving, you would draw 30 amps.

The amp isn't capable of that level regardless. After 120 watts rms the amp is going to keep pulling more and more power though, to try and make the power the user is asking for, even though it can't. This is called saturation.

Saturation:
A condition in which high amplitude signals on a display do not increase with increased gain and appear flattened. This is described in terms of the audio signal outputted form the amplifer as clipping. Clipping singals produce alot more heat and hence are alot more likely to smoke a driver.

Heres a basic description:
D/C Clipping
When an amplifier is driven beyond its potential (40 to 50 % for most stereo receivers), the amplified audio signal will begin to clip. Clipping is the distorted sound heard when the volume is too high. This clipping is seen as D/C voltage, therefore, the amplifier will see only the D/C resistance of the coil in Auto-former based products (1-2 ohm), not the A/C impedance of the whole circuit, causing the amplifier to shut down or potentially damage it. This D/C voltage will eventually cause damage to all auto-former based products used in the system. Resistor based products are also designed for A/C not D/C and they too will suffer damage due to over heating caused by clipping. Resistors produce considerably more heat when driven with D/C that can cause component failure.
http://www.capitolsales.com/tech-dc-clipping.html

[Wingman21]

Did the dealership buy the new sub?
Odd that they'd buy a cerwin vega sub.

Being a 4 ohm sub, it will force the amplifier to draw theoreticly twice the amperage that the other sub did. Realisticly it will cause it to draw about 50% more. This is definitly a reason that the amp might be blowing its fuse.

Which amp do you have?
The MSP had 2 diffent ones. The KAC-5201 is only rated for a 15 amp fuse so it should be fine regardless. The older amplifier, the KAC-529 was a little less effecient so that would be a little more likely to pop a fuse.

What is the model number of the new sub?
Keep in mind that suboofers handle power, they do not create it. So a 400 watt subwoofer (although ususaly a major exageration expecialy for an 8") means that it can handle up to 400 watts. Be that power rms, peak, or imaginary I wouldn't know until you tell me the model number of it.Yep, Mazda paid for it. My stock setup always rattled like hell and the sound was coming directly from the sub so after changed the stock sub 2 times my dealer tried an other model but the rattle was still there :(! So now I got that sub instead of the stock one.

For the 400w, hope it is true because if its not Im gonna pay a visit to my dealer ;) !!!
Im gonna check the model number for the sub and the amp when I'll get back from work :) !!!

Thanks

[1sty]

For the 400w, hope it is true because if its not Im gonna pay a visit to my dealer ;) !!!
Im gonna check the model number for the sub and the amp when I'll get back from work :) !!!

Thanks
there is nothing you can really compain about with the dealership. An advertised 400 watt sub doens't mean dick. Hell audiobahn advertises subs as being 700 watts and they can't handle a steady 250. On the other hand JL audio has 400 watt subs that can handle 1000 watts rms. There is no standard to rate subs by so most manufacturers invent there own. The more full of crap the manufacturer is, the more BS'ed there ratings will be. Additionaly there is a very big difference between a peak power rating and an RMS power rating. Both are subject to non-standardized rating meathods.

[jurgs01]

I know what saturation is. You can see a basic example of it in a ideal op-amp. I also know there is loss inside the amp. An amp cannot make power though (as you probably know. It is using the power it draws from the battery to amplify the audio signal. Power is conserved in ideal circuits. I know this is not ideal and there are losses, and that's why there is a specification section in back of the amp's manual.

[1sty]

An amp cannot make power though (as you probably know. It is using the power it draws from the battery to amplify the audio signal. .I am well aware, unfortunitly, most of those new to electronics have a hard time understanding that fully so to simplify it, most of us will say that the amp makes the power and the driver handles it. Mostly to point out that a subwoofer shouldn't be judged by a wattage rating like an amp should. I had one member even tell me he had a 2400 watt system because each sub was 800 watts and each speaker was 200 watts. (evil)
Baby steps

Obviously, the laws of thermodynamics tell us that not only can an amplifier not create power but that it can not even convert 100% of the power it does use.

[jurgs01]

1sty, what's your job again? You seem to have a little more knowledge than some of the car audio installation guys I know. They usually know that a product will do something, but most don't have a clue as to why.

[1sty]

1rst, what's you job again? You seem to have a little more knowledge than some of the car audio installation guys I know. They usually know that a product will do something, but most don't have a clue as to why.I am a comercial level A/V installer. I learned most of what I know from the car audio world and my breif education as an electrical technician. Most installers are definitly happy just knowing how to hook something up, I want to know why we hook it up and how it works.

[Wingman21]

Im gonna check the model number for the sub and the amp when I'll get back from work :) !!!

Thanks
Model number isnt indicated on my service bulletin so Im gonna call my dealer. For my amp I forgot to check and now its too damn cold outside... tomorrow :) !!!

[TxSpeed59]

anyone have a pic of the wiring on the stock amp? I think mine isn't right..

thanks!