View Full Version : a new amp
supra steveo
22-12-06, 00:59
as some of you know ive blown my 600 watt kenwood amp had it bridged and it was powering a JL audio 12 w0 after 3 hrs of good running it went pop ( the amp that is ) so now with no bass i am a bit peeved off to say the least so have been looking to get a new one dont want to pay massive money looking at about £100, must fit under the seat and i guess it needs to be fan cooled looking on ebay i seen this any one rekon it would be any good ?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=014&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=330062423499&rd=1&rd=1
Motorworld do a splx 1000w amp for 130 quid but yo0u can get them on fleebay for about 40-60 quid.
Ive got 1 powering 2 alpine r type 1000w subs with no problems at all. Sounds great.
Motorworld do a splx 1000w amp for 130 quid but yo0u can get them on fleebay for about 40-60 quid.
Ive got 1 powering 2 alpine r type 1000w subs with no problems at all. Sounds great.
supra steveo
28-12-06, 18:07
news on my amp issue
i had blown the 2 fuses on the side of the amp i couldnt see so ive replaced them and the amp still doesnt work i have tried my bro`s crappy little caliber amp and that just cuts out when i turn the music up so ive booked it in to get it checked at a local sound specialist in newcastle ( sounds alarming )
i think the amp is dead and i think i am just going to replace the amp with a alpine one its a 700watts amp running 300 RMS if that means anything to anyone??
supra steveo
28-12-06, 21:58
more news
when i had replaced the 2x 20 amp fuses on the side of the amp i blow the inline power fuse, the amp was working for about 10 mins then blew the 2 fuses on the side again,any ideas ?? well replaced them again and turned the gain down and its ok now
if anyone can give me some help on understanding this amp abit better i would be really grateful
now ive turned the sensitivity down to 0.5v will this make any difference to the amount of heat and stuff with the amp, i am hoping it wont blow now, but at least the amp is working now and i know its not terminal :D
SupraJames
29-12-06, 18:35
Sounds like you were running the amp with the gain too high, which would cause it to blow the fuses if pushed too hard. Turning it down should help with the overheating problem to.
supra steveo
29-12-06, 19:26
aarrrgghh BOLLOX
the amp has just blown another 2 20 amp fuses on the amp after 15 mins of running the amp on half power, i am seroiusly cheesed off now any more ideas what it could be ? the amp wasnt even hot, i think the amp is fooked now, could a bad earth be the cause of the problems? and what is the lenght of earth cable i can use
i am sure the power cable is ok
i think the earth cable is ok just need a way of checking it
the remote cable couldnt blow fuses could it ? i wouldnt have thought so
so that leaves me with just the earth cable i need to investigate but really i think i just hammered the amp on the way home it was really hot ? help .....this is doing my nut in now
SupraJames
29-12-06, 19:32
Could be earth connection, what gauge wiring are you using ? and where is the amp earthed to..? dont think it could be the remote wire as its such a weak 12v source.
supra steveo
29-12-06, 19:34
i earthed it on the bar under the passenger seat i didnt want to start putting holes in the floor
supra steveo
29-12-06, 19:35
gauge wire is pritty big same as the power cable size
amps can be very picky... have you DEFINATELY got a good solid 12v input? One thats not majorly fluctuating (especially when you switch on the engine which uses the starter motor).
What are the full specs of the amp when in bridged mode??
You need to make sure that the impedance (ohms) of the speaker are right too. For example - the amp might be rated at 600W peak power (which is somewhere around 300W RMS) into 4 ohms... if your speaker is an 8 ohm model then you'll only get 1/2 the wattage, and it puts much more strain on the amp, and hence can blow things up.
This could also explain your overheating issue. More strain on the amp makes it work harder.
So, check the full spec on the amp (in std and in bridged mode), and then check the specs of the speaker.
Post all up here and i can have a think :)
The +12v and 0v cables should be large gauge - perhaps 4awg.
The remote cable needs only to be a thin cable - and it's only around 20mA that is sent out from your remote source.... that is assuming your head unit is only putting out 20mA down the remote cable.....?
SupraJames
29-12-06, 19:48
Min I would recommend cable wise is 4AWG for a 600w Amp, not too sure on your ground connection though, may be worth running a new groud cable just in the car to the boot and ground it on one of the big bolts there (will get a pic of mine later). Then if its all good then run the cable along the door seal, easy to do.
Assuming it is a 300W RMS amp, you'll find you will be drawing 25A from the battery. So yeah, 4awg cable needed. However, i wouldnt have thought this could be a reason as to why the amp blows.... the cable would melt/break if it wasnt thick enough (dangerous/fire risk of course, which is why u need thick cable!)
supra steveo
29-12-06, 20:03
http://images.google.co.uk/imgres?imgurl=http://img.shopping.com/cctool/PrdImg/images/pr/177X150/00/01/3c/81/f7/20742647.JPG&imgrefurl=http://www.shopping.com/xPF-Kenwood_100W_x_2_Amplifier_KAC_728S&h=150&w=177&sz=6&hl=en&start=3&tbnid=Rq7Ahsm27HKgzM:&tbnh=86&tbnw=101&prev=/images%3Fq%3Dkenwood%2BKAC-728s%2B%26svnum%3D10%26hl%3Den%26lr%3D
this is the one
supra steveo
29-12-06, 20:07
looking at this now i am just thinking because it ran 2 jl 12W0`s ok both bridged together
aarrrgghh i think i need a new amp
supra steveo
29-12-06, 20:16
can amps blow fuses coz i am not using all the power they can put out?
supra steveo
29-12-06, 20:27
http://images.google.co.uk/imgres?imgurl=http://www.lightav.com/car/jl/12w01.gif&imgrefurl=http://www.lightav.com/car/jl/sub.html&h=90&w=72&sz=6&hl=en&start=6&tbnid=w8Kuqmt1TiBLHM:&tbnh=78&tbnw=62&prev=/images%3Fq%3DJL%2B12%2Bw0%2Bsub%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN
this is the sub the 12 w0
supra steveo
29-12-06, 20:29
iam now watching a larger sub on ebay to a jl audio 12 w3
right.... so am i right in thinking:
You have a Kenwood Amp - 100W x 2 (into 4ohms)
Which you have then bridged to give 200W x 1 (into 4 ohms)
And then run
1 x 12w0 sub (125W) from the output of the amp?
so 1 set of wires coming from the amp terminals going to the speaker. (1 +ve and 1 -ve cable)
If so, there is nothing wrong with that setup. Only think I would worry about is blowing the SPEAKER as you are capable of 200W, but only have a speaker that can handle 125W.
Amps do NOT blow fuses because you aren't using the power they can produce. You'll just find that the amp will be rather cool as you won't be making it do much work - think of it like a car engine - if you pootle about at 25mph it'll take ages to warm up - run same engine at 100mph and it'll be cooking!
looking at this now i am just thinking because it ran 2 jl 12W0`s ok both bridged together
Sorry mate, you've lost me there.
What was bridged together? The amp channels? Or the speakers?
supra steveo
30-12-06, 00:17
right.... so am i right in thinking:
You have a Kenwood Amp - 100W x 2 (into 4ohms)
Which you have then bridged to give 200W x 1 (into 4 ohms)
And then run
1 x 12w0 sub (125W) from the output of the amp?
so 1 set of wires coming from the amp terminals going to the speaker. (1 +ve and 1 -ve cable)
If so, there is nothing wrong with that setup. Only think I would worry about is blowing the SPEAKER as you are capable of 200W, but only have a speaker that can handle 125W.
Amps do NOT blow fuses because you aren't using the power they can produce. You'll just find that the amp will be rather cool as you won't be making it do much work - think of it like a car engine - if you pootle about at 25mph it'll take ages to warm up - run same engine at 100mph and it'll be cooking!
What was bridged together? The amp channels? Or the speakers?
what i used to do was run 2 jl audio subs off the bridged amp as i was told i would get more out of it ( i.e 2 speakerwires 1 teminal) ??? means fook all to me anyway?
so what ive done now is run the one sub off the amp still bridged and it blowing the fuses the sub is ok i think its just the amp keeps blowing or unless its doing that to stop me from blowing the sub ? i turned the out put down to half now any way and it still blew the fuses so i am lost now
BTW the amp was red hot after a 3-4 hour run and could smell burning then amp was turned right up to full and the sub seemed to be taking it pritty well the amp was bridged too,
something is bust isnt it :(
right - your original set up was pushing the amp to the absolute max.
2 4ohm speakers running like you have mentioned is called running speakers in PARALLEL.
In Parallel mode, you basically 1/2 the impedance of the setup. (it is product/sum - so 4*4/4+4 = 16/8= 2.
So you were running a 2ohm system.
The amp was rated at 150W x 2 (at 2 ohms) - and so bridgeable you would have 300W x 1.
Now, if you were running that setup for a while, and using it quite loudly, you were pushing BOTH the AMP and the SPEAKERS to their absolute maximum. The amp would have got quite hot.
How long did you run that setup for? Chances are you pushed it too hard for too long, and now you've damaged one of the channels, one of the output transistors or something.
Can you open the amp up? Can you see any burn marks on any components, brown sections of the board or anything?
IF YOU ARE BRAVE:
You could try switching the amp to NON-Bridged mode. Then run each speaker off each channel, and see how it goes. However, I say Brave, because chances are the amp is already f00ked, and you might just make things worse. A Burning smell/smoke is NEVER a good sign, and it's dangerous.
I'd probably either get someone to look at the amp, or get a new one.
If you have a multimeter to hand, you can always stick it to resistance mode and measure the resistance across the 2 connections on the speaker, to make sure both your speakers are 4ohms, and if both say 4 then you are ok - if one says something totally different, or worse, nothing at all, then you'll have a problem.
Sorry to go on and on above, but it can be quite complex to explain :(
supra steveo
31-12-06, 00:36
cheers pablo
i was running the 2x 4 ohm jl`s on the kenwood for quite some time and it sounded really good.
i was running it with just 1x jl for about 3 month and only running for about an hour here and there each time and that to sounded real good and loud but the 3-4 hrs run has done the damage it think dont know why it keeps blowing fuses but it does while bridged i might just use one terminal not bridged tomorrow just to see what happens
but i did go and spend some pocket money today on a new amp and one that fitts nicely under the seat, its an alpine MRP-M450 it says 800watts max on the box for some reason but the output is 220w x1 RMS @ 4 ohms and 400w x1 @ 2 ohms ive been told if i get a sub with a duel voice coil then make sure its 4ohms the amp fitts nicely under the seat loads of room so ive went and bought a wee 6 cm pc fan i am going to wire up to the back of the ciggy lighter to help with cooling the amp so i dont have any more problems with heat, the only problem is i dont think its working the sub enough it sounds like the front speakers are doing all the work i will take the car car back after the new year to do the levels properly the lad who looked at the car said with my sub he would use the amp like this and set the levels low on the amp but i can hardly hear the sub
What you need to understand is the Wattages i think.
When someone quotes a wattage such as 800W MAX - the MAX indicates that it is PEAK power that it'll do for about 2 seconds before going POP.
RMS is the TRUE Wattage. (or as close to it as possible)
RMS is approximately HALF the MAX/PEAK/PMPO wattage.
In all truth, MAX wattage is total and utter bullsh*t. Make sure when you compare things you are comparing the RMS values, that way you'll have a good idea.
The other thing you have to watch for is what the wattage is quoted into.... by this i mean impedance.
Your new amp is a 400W RMS amp into 2OHMS. So, if you have a 2ohm speaker, you'll need a 400W model. When you increase the impedance (like in your case you are using 4ohm speaker) the output of the amplifier drops, and again in your case it drops to 220W RMS.
If you have a really big wattage amp, and small wattage speaker, the speaker will be loud but you risk making it go pop.
If you have a really big wattage speaker, and a small wattage amp, the speaker will be quieter but the risk of the speaker going pop is tiny.
To get a big wattage out of an amp - the amp will need to be physically big. To get a big wattage out of a speaker, you generally need a large magnet at the back.
Why don't you make sure your headunit is setup so that you increase the bass output - either using the EQ or amp output level?
Anyway, enough of confusing you - good luck!
supra steveo
02-01-07, 21:55
balls! balls! balls!
it wasnt the amp it was the sub ive buggered the voice coil and my kenwood amp is ok apperently the voice coil is burned and down from 4 ohms to .13 ohms so ive gave it a good hammering (oops) so because the sub was knackered the amp was playing it safe and blowing the fuses ohh well that was expensive ,well i guess you can call it a good lesson ive learned how to check quite a lot of things to find faults now anyway
any one want to buy a nice kenwood amp?
ah that makes more sense. Tis the reason i suggested putting a multimeter across the speaker terminals and check the impedance....
good luck with sorting things out!
Speak to Chiefgroover on here too... bit of an ICE-god who will recommend good things, so i'm told!
Just don't fall into the silly trap of comparing different wattages - RMS and Peak/Max output are totally different!
Your speakers are 125W.... the amp was 200w - obviously the amp has pushed the speaker too hard and melted it.
supra steveo
03-01-07, 01:15
yeah i know about peak and RMS now the alpine amp ive got under the seat at the moment shout be being cooled by a 6 cm PC fan ( well it will do when i run the cables up to the ciggy lighter ) i dont want to run the fan off the remote i dont want it to fuck about with the amp
is the area under the seat that restricted then?
These amps don't NEED fans.. otherwise they'd have them built in (and some do)
That said i hate running amps in conditions where they have restricted airflow.
supra steveo
03-01-07, 13:49
i hate running amps in conditions where they have restricted airflow.
thats why i thought i would give it a little extra help with the flow of air
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