speaker thump

[peter65]

hi guys... i have an eclipse 8012 head unit with a Response 4x100WRMS Digital Amplifier, in my vp commodore exec, and when i turn the ignition off i get a massive "thump" in the speakers. The amp power is controlled by the signal wire from the head.

The power for the amp comes (via 4 or 8, cant remember, gauge wire) from the sub fuse box in the engine bay, which is constantly powered. i chose that spot as it was a spare fuse position... i just had to fit a large spade connector and whack a fuse in.

any ideas how to stop the thump.

Cheers and thanks. pete.

[peter65]

sorry all - it is an Eclipse 8061 head....

[azzfox]

The power for the amp comes (via 4 or 8, cant remember, gauge wire) from the sub fuse box in the engine bay, which is constantly powered. i chose that spot as it was a spare fuse position... i just had to fit a large spade connector and whack a fuse in.

uhhh, just a Q.. what gauge cable is it before the spare fuse position

[peter65]

hey azzfox... its a solid metal "rail" inside the plastic fuse housing...

[azzfox]

yes, but what gauge cable is between the fuse box and the battery.. just doesnt sound right to me. what made you do this instead of adding a ring terminal directly on the battery?

[peter65]

ok i get you... the fuse box is part of the vehicle.. there was a spare position in the box (for a higher spec car they use it for something) with the "live" side precabled into the vehicle wiring loom and then to battery as part of the vehicle wiring... i used that as it seemed good to keep it all stock... cheers pete.

[littlejon]

Have you tried wiring straight to the battery to see if this stops the problem?

[peter65]

hey littlejon - thanks for your post. no i havent, but its a good idea and will try it on the weekend. thanks for the suggestion. btw.. .dont spose you will have this problem when you get your ssv (green with envy) hehehe.

[kopper69]

I would be going with a bad earth or head unit. If your head unit is not earthed properly it will earth through your antenna, but normally it would do it when you turn the head unit on too. I would be going over all electrical connections and making sure they are all super tight and super strong. Any dodgy ones, particularly power and ground, fix up.

[Luke0011]

I think its in the amplifier , but i would do what kopper says and check the earth and power connections, as well as adding your own fuse in the engine bay and keeping it away from the fuse box. if all else fails use a turn off pop module from stinger. Cheers

[garfa]

peter: as said before the current cabling in any of ther fuse box will be useless compared to the 4 ga.
wire it straight to the batt pos terminal and have the fuse holder less than 40cm away from the batt.
speaking of fuse holders: what type are you using and what is the fuse rated to?

[Not_An_Abba_Fan]

I have the same thing in a brand new Triton. The last two I have had does is, but only with bluetooth on. I'm guessing from the above posts it is something to do with the way it is wired in. Doesn't really bother me, I only do about 5000kms and I get a new one.

[peter65]

all... thanks for the posts...
kopper69: it does do it at turn-on too but not as bad.

Not-an-abba-fan: the fuse holder i am using is a spare postion on in a sub-fuse box under the bonnet (also contains the "main" fuse, "engine" fuse and another couple) with a 20A large (plastic body/clear cover - sounds weird i know...) fuse.

Luke 11: this is the second amp - the first was replaced under warranty as one of the channels was RS. Cant remember if that one "thumped" too...

So the plan for the weekend is to check head unit earth first.... (Ahh the dash in pieces again...). If that does not fix it then its a power rewire (with new fuse holder) ahead...

Cheers all and thanks for the suggestions... i will update the post later....

[Not_An_Abba_Fan]

Rather than stripping everything out, can you access the wiring? Just run a heavier guage wire straight to the battery temporarily to see if it stops the thumping.

[peter65]

Hey not_an_abba_fan... good call... but i cant get to the head wiring without pulling it out... i will give it a punt... its not that hard.. i have done it a few times now.

....in the light of kopper69's comment about a bad head-earth would cause it to ..." do it on turn on too", i thought that was probably the likely culprit.

anyway... into it tomorrow!

cheers and thanks... pete

[wh33lzz]

Yeah its the amp. an internal cap is discharging unused amplified power and causing a low freq "thump" discharge on turn off.

To troubleshoot, start with your earths, make sure if you have 4 guage power, you use a 4 guage earth and its to a clean unpainted part of the chassis.

If you have a monoblock with 1000 watts RMS up its sleeve, its almost impossible to completely get rid of the thump, but under that, earths sholud solve it.

[peter65]

guys... an update.... wired the amp power directly to the battery on sat... same thump... no change. didnt have time to play earth detective. tomorrow's a day off... cough cough... so might get some time then... hehehe

wh33lzz: thanks for the explanation... i am using the same gauge wire (4 or 8, cant recall) for the amp earth as i am for the amp power (but different colour...) & will check the body connection - maybe it is not as good as it can be...

its a 4*100 watt amp so it should be solvable... i want to eliminate as much of the noise (and possible speaker damage) as possible.

cheers all and i apprecaite your help.

[peter65]

hey all... bit of an update.

I have now wired the main amp 8G power wire (temporarily) into the "accessories" circuit in the back of the fuse box. So when the ignition is turned off it loses power straight away which appears to have made the thump disappear. before the main power to the amp went to a constant 12v power source (the amp didnt draw any power when switched off as the blue "trip" wire from the head was off, thus the amp was off).

So now the task is to wire up a relay off the acc cct (so the relay coil is the only current drag on the accessories cct) that, when energised, switches the main power lead to the amp.

i will run it the way it is (ie dodgy!) for another day or so to monitor it before i start wiring up relays and stuff.

cheers and thanks to all for the advice! pete.

[garfa]

pete:why not just wire it to the to the batt. did you have a good play with the earths?
think about this mate: what sort of current is drawn through the acc circut? now what happens when the acc is already loaded and you add the amp into that.
you will burn wires and possibly the acc fuse holder. something will go woof soon mate.

[peter65]

hey garfa... thanks for the feedback..

i had the amp wired to constant power before (via a 20A fuse) in a spare under hood fuse box postion.... i tried to minimise the chnges to the car wiring...

re the earths... yep installed a bare-metal earth nut/bolt with 8 ga wire and lug into the rear seat support bracket adjacent to the amp... so that earth should be ok... and i measured the HU earth and it was ok... cant remember the reading... couple of ohms from memory...

you are spot on about loading up the ACC circuit with another 20A of amplifier current.. thats why i said above that the plan is to use the ACC cct to power a relay, which will switch the main amp power (so the only extra load on the ACC cct will be the relay coil (which i am guessing will be about 500mA???).

One more q that i am yet to resolve is: am i better off using the ACC cct to turn on the relay or the blue wire (remote power on, used to turn the amp on/off) from the HU? any opinion on that?

cheers pete

[garfa]

pete: where is the feed currently running? through what and whats the fuse holder?

acc circut will be fine but whats the relay you will be using? that amp will pull around 40-50amps if around 75% efficent.

[azkwazere]

i dont know why this is being discussed.

Your talking about not wanting to make to many changes to your wiring but your going on about wiring into ACC circuts and tapping into fuse boxes.

This isnt a hard task. Run an 8 guage wire DIRECTLY from your positive battery terminal to a fuse no more than 30cms away. Then, run another 8guage wire to your amp from the fuse. Earth your amp no more than 30cms away using a ~8guague wire (lets be pedantic and) to a bare metal part of the car. Ensure its secured tightly.

I havnt seen any issues related to wiring triggers into acc circuts directly HOWEVER, i dont personally. I have custom +ive circuts all throught my car using relays and higher guage lines. The wire from HU is fine, thats why its there.

Amps draw alot of current, they need a CLEAN power supply, that means solid +ive and a well earthed -ve. ITS SIMPLE CAR AUDIO STUFF.

(ps. I assumed 8guage wiring as thats what was being discussed, didnt work anything out using maths)

aZk.

[peter65]

Guys,
thanks (again!) for the feedback and suggestions.

An update:
installed the relay for the amp power.... used the trip for it from the load side of the radio power which is switched from the Acc terminal... shazam.... thump gone! I tried using the HU blue wire for the relay trip but the thump was still there.

the explanation that i read in another forum (rightly or wrongly - dont know) was that if constant power (triggered by the HU blue wire) is used, there is enough power in the MOSFET output stage of the amp at switch off that needs to discharge somewhere -
and that is thru the speakers.

aZk,
you are right. it is all simple and often the simple steps (ie good earths) are the ones that are overlooked and cause all of these annoying little problems. thanks for your advice - i appreciate it.

cheers all and thanks again...

Pete

[peter65]

garfa - soz did not answer your q's....

the amp has an inbuilt power fuse - is that enough? or do i need an additional (in line) fuse near the battery?

i am using a 30A Bosch relay and 8 gauge wire both for power and earth. i that figured if the power fuse in the amp is 20A then a 30A relay should suffice.

cheers... pete

[peter65]

hmmm just reread aZk's comment about the proximity of the fuse to the battery... looks like an in-line is needed...

cheers pete