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General => Car audio => Topic started by: Mars Attacks on 08 February 2005, 21:32

Title: is my amp knackered?
Post by: Mars Attacks on 08 February 2005, 21:32

Now then,

been running a basic, reliable sound set up in my car which has been transfered over from my last 3 gti's basically it is a boxed 700watt sub with a 4 channel 350watt amp running it. its worked like a treat until the other night when i was driving along listening to a bassy tune when the sub just stopped working with no warning. rest of speakers run from head unit were fine.

looked in boot and power protection light was on amp. thats never been on and i thought maybe a fuse had blown. checked both the fuse on the amp and the fuse on the power line from the battery and both were fine. i tried taking off the battery power and then reconnecting, but that just causes the sub speaker to "pop" and the power light to come back on again. I have tried different speakers and no speakers at all, but same thing. soon as you attach the main power lead, the power protection light just comes on.

I have checked the earth lead and that is fine.

is it just a case of a knackered amp? i've hammered it pretty much for the last 2 years and it was pretty cheap so i wouldn't be surprised. just wondered if anyone had any other ideas i could try.

Cheers

Title: Re: is my amp knackered?
Post by: Overseer on 08 February 2005, 21:44

doesnt sound too good... usually amp problems are down to a dodgy earth or the fuse..

i'd really suspect the quality of the earth.. i had a bad earth on my old car that would stot working randomly.. i thought it was  good at hte time  :embarassed:


what happens if you repeat the test you did with removing the power/reconnecting BUT with the earth?

Title: Re: is my amp knackered?
Post by: Mars Attacks on 08 February 2005, 22:00

i'll give it a try, cheers  :smiley:

Title: Re: is my amp knackered?
Post by: bunter on 09 February 2005, 13:13

yeah i would seriously check all the cabling, not just the Earth. Also if your boots a bit crowded then the amp could overheat which would cause the Thermal Overload switch to cut in. Some amps have to be reset by a professional when that happens. :cool:

Title: Re: is my amp knackered?
Post by: Judderi on 10 February 2005, 17:03

also check that the fuse your using is the correct rating.

Title: Re: is my amp knackered?
Post by: Mars Attacks on 11 March 2005, 10:31

thanks for the help, turned out the amp was shafted so i invested in some new gear.

bought a 4 channel 600watt JBL amp. My question here is, i've bridged 2 channels to power the sub and am left with 2 channels remaining. Can I use them to power the 6x9's in my shelf rather than just speaker wire from the head unit.

the amp seems to be in the form that 2 channels are marked as "front" and 2 as "back" each with seperate RCA inputs. I've only got one RCA input coming in from the head unit to the one marked "back" and the sub is wired up to the 2 channels marked "back" on the amp.

My question is, would i need a 2nd rca input coming from the head unit to the input on the amp called "front" make the remaining 2 channels labelled as "front" work?

I was hoping that my one input from the head unit would work over all the channels on the amp, but not so sure now.

sorry if that made no sense!  :shocked: but i'm new to this lark.
Cheers

Title: Re: is my amp knackered?
Post by: Judderi on 11 March 2005, 10:51

In a corrct setup you should do one of the following.

My head unit has rca outs for front, rear and sub. So if yours is the same you should be using the rca's from the sub out to plug into the rear bridged channel on the amp with the cross over set to low pass.

(http://img205.exs.cx/img205/6950/amp17si.jpg)

If you dont have a sub out rca channel on the head unit use the rear outs instead. Then use the front out rcas on the head unit, running another cable to the amp using the front channel with the cross over either set to high pass or no on at all. Idealy i would use the front channel on the amp to power your front speakers not the 6x9's as you will get much better quality of sound with the cross over set to high pass. Just run the 6x9's off the head unit. The 6x9's are really only for people sat in the back. Your sub will do all the bass work and your fronts will provide the quality of voice and highs with no bass. Its all a little confusing so i will draw some diagrams.

Another option if your feeling lazy and a bit cheap is to buy a set of Y splitters for the rca cable. This way you can use the same cable to power both channels on the amp.

(http://img205.exs.cx/img205/6630/amp25ow.jpg)

Title: Re: is my amp knackered?
Post by: Mars Attacks on 11 March 2005, 11:10

yep thats the problem, my crap sony head unit only has one pre-out.

looks like my only option is to get better head unit or those Y splitter things!

Cheers

Title: Re: is my amp knackered?
Post by: Diesel_head on 13 March 2005, 13:43

do you want some Vibe QB69's.. i got them for ?100 not long ago and have urgraded all the wires with decent ones... if so make me an offer.
                             josh