Are fuse blocks & giant wires REALLY necessary?
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Silver Member Username: CheapskatePost Number: 578 Registered: Mar-04 | i'm trying to wire up a bicycle trailer system and have never done car audio. last night i bought a "dual amp" power distribution fuse block. i don't really see the point. my 2 amps already have fuses of their own and adding another one seems redundant and a waste of money. even more ridiculous, the power block clkaims i need ANOTHER fuse for the + (or -?) line. that sounds like total "give us more money" BS. all you should need is ONE fuse to break a circuit, not THREE! i'm also having a hard time wrapping my head around 4-8 guage wiring too. home gear pushes 5-7 X 100+w through plain old 16-18 guage zip cord. not only that, but i can't see how 1/2" cables can be wired into those tiny darn screw terminals on the amps. if i had my way, i'd just wire everything straight with workable 10 guage wire. i can't see being able to solder 4-8 gauge cable to the toggle switches i planned on using for turn on/off either. why can't i just use realistic size wire and the amps' onboard fuses? the only thing i can really see being able to connect to such massive cables are those fuse blocks which i'm not convinced i even need to begin with. for what it's worth, i have 2 150w X 2 class A/B amps (which i intended to wire seperately for power) and an 800/630amp battery. i was going to bridge the sub amp into a 150w sub thinking it would be easier on the amp and give a little extra headroom. is it really a bad idea to wire this system no frills style? |
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Gold Member Username: Nd4spd18Northwest PA Post Number: 8119 Registered: Jul-06 | " my 2 amps already have fuses of their own and adding another one seems redundant and a waste of money. " Any time a power wire connects to a power source (such as a battery) you MUST have a fuse there, rated to match the gauge of wire. Scroll down to find what wire size and fuse size you need http://www.bcae1.com/wire.htm Also a good read http://www.bcae1.com/fuses.htm " even more ridiculous, the power block clkaims i need ANOTHER fuse for the + (or -?) line. " Any time you reduce the size of a wire (such as at a distro block) the smaller wire must have a fuse rated for that wire. " i'm also having a hard time wrapping my head around 4-8 guage wiring too. home gear pushes 5-7 X 100+w through plain old 16-18 guage zip cord. " What comes out of your household wall outlets is alternating current (AC). Your car battery produces direct current (DC). DC requires MUCH larger wire than AC to carry the same amount of current. More info on that http://www.bcae1.com/acdc.htm " i can't see being able to solder 4-8 gauge cable to the toggle switches i planned on using for turn on/off either. " Those switches probably cannot handle that amount of current either. Put the switch in the amps REM wire, thats what it's for, to turn the amp on/off. " is it really a bad idea to wire this system no frills style? " That may be the worst idea you will ever have.... a wire not fused properly WILL burn if it shorts to ground. And given how hot it would get from the massive amount of current supplied by a car battery, would most likely ignite anything in contact with it. |
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Silver Member Username: CheapskatePost Number: 579 Registered: Mar-04 | OK, thanks for your help. i thought that AC & DC were the same except for AC's "back & forth" flow. i planned on putting the switches on seperate circuits for the turn on/off with a 12v tail light as an on/off indicator as well as actual tail lighting. the switches were rated at 12v X 20 amps which seemed adequate to me. i was originally going to use class D blaupunkts which were rated for 20 amps too. so, if i need such huge cables, then how the heck am i supposed to connect them to those tiny little spade terminals? i seem to remember "the good old days" when i never saw car stereo installs with inline fuses or capacitors. better safe than sorry, but i just don't know how i can get a wire bigger than my pinky to fit in a space no wider than a pencil. i tried to google "how to hook up a car stereo amplifier" articles, but they didn't help as they're all about actual car installs and not "direct grounded" battery only etc. BTW i don't really need fuses for both + & - wires do i? |
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Silver Member Username: CheapskatePost Number: 580 Registered: Mar-04 | i don't know if my application will really require large cables after skimming the 1st article. (great info BTW, the sites i found sucked!) i have no intention of running either amp anywhere near close to clipping. i only bought those amps (power acoustic plasma sphere) for their cool plasma lights. technically, i'd be running the sub amp at 1/2 power if i DID max because my sub is only rated to 120w so i'd get cone smacking before clipping if i bridged that amp. i'm not trying for max SPL, just high SQ with more power than my puny 10wpc sonic impact and subs larger than my mission M71's (5 1/4" 2 ways) looking at the math, it would seem 10 guage should be adequate for playing at sane volume levels with 93dB sub efficiency and 92dB main efficiency with rolloff. i still need to build a frame to hold everything, so i'll hold off on wiring until i read those two pages from beginning to end. thanks again for your help.  |
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Gold Member Username: Nd4spd18Northwest PA Post Number: 8132 Registered: Jul-06 | Switches in the power wire is just a bad idea, run constant power and switch the REM wire, thats what it's for. If 10 gauge will carry enough current you can use it but you have to use the right size fuse for that wire. If that fuse blows, you used too small a wire. And no you never need fuses on ground wires. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 12156 Registered: Dec-03 | the gauge of the power wire is dependant on the length of wire, and the amount of current it carries. if the wire is too small, the current will build heat, and melt the wire housing, causing a fire hazard, along with a lack of proper current flow leading to clipping of the amplifier(s), causing distortion, and speaker damage. the power cable is neccesary. the fuses are there to protect both the equipment and the wiring. the fuses aren't NEEDED, but are highly recommended. |
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Gold Member Username: Nd4spd18Northwest PA Post Number: 8161 Registered: Jul-06 | Most people consider it necessary when not having it creates the risk of a fire. |
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Silver Member Username: CheapskatePost Number: 581 Registered: Mar-04 | point taken. i already bought a second fuse block for the negative lead and will also add small inline fuses for the power switch and tail lights now that i know WHY they're needed. i thought it was for power surges and not ovetaxing wire. i'm running 4 gauge to the fuse blocks and 8 gauge out. i thought that 4 gauge was that HUGE wire i've seen in car shops (2 gauge? 1 gauge?) and was surprised how small 8 gauge was. i've done it right, don't worry. better safe than sorry... agreed. i always planned on putting the switches on seperate lines. i guess i wasn't clear there. the only problem i'm having now is that 8 gauge is too big for the ring lugs i bought for the power ins on my amps and when i pried the "crimps" open, the darn wire proved solderproof! all i managed to do in 20 minutes of soldering was heat up about 8 inches worth of cable. why do amp makers use those tiny terminals that lugs of the right size won't work with 8 guage wire with? i'm just going to recut the lumpy soldered ends and run them into the amp bare. i'm not going to buy $$$ audio lugs AND a crimping tool i'll only use once. i always prefer to solder my connections anyways. once i assembled one half of the power distribition, i tested both amps and am quite happy. they sounded alot better than expected for class A/B (i'm a class D convert) and those plasmasperes look better than pics. they have a nice electric blue tint. i WILL be adding a high power guillotine switch to the negative main so that i can easily connect and disconnect the battery instead up pulling fuses every time i pull or drop the battery. i live on the 2nd floor so i'll be hauling the battery & speakers seperately from the trailer. now all i need to do is assemble the trailer and it will be ready to get wired up. eventually i'll build a bigger and badder trailer system with EL wiring, ground effects lighting, TQ chiller EQ lights and even a disco ball (really!) but for now i just want to get up and running. thanx a bunch for all of your help folks and stay tuned. if you're interested, i'll be putting pics of the installation on my street party bicycle webpage when it's done. |
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Gold Member Username: Th3pwn3rI compensate... Post Number: 8600 Registered: Jul-06 | "the fuses aren't NEEDED, but are highly recommended." X2, I was actually going to say that myself. I dangerously ran my system without fuses without any problems but I took some precautions so that things didn't move around and help a potential fire start easier. |
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