Amp and Sub Question.

[jmc330i]

I installed an amp and sub into a mates car yesterday and other than the usual probs of routing the wires, it all went well and worked first time

The only thing is, when the headunit is turned off, the sub 'thumps' once.
The headunit didnt have any RCA outputs so I used a converter running off the rear speaker channels (no rear speakers at the moment).

I remember having the same problem in my first car when I also used an RCA converter, but cant for the life of me remember what the problem was or how I stopped it.

Anyone got any ideas??

[chu346]

You need to change the time that the amp turns off, compaired to the head unit. Some head units have two or three remote wires that are delayed at different points to stop this.

You can try to connect the remote wire to a different switching source, such as the ignition switch or differnt remote wire from the head unit if it has one.

[jmc330i]

Thats a good point. On my Cav I think I solved the problem when I changed headunits from the original Grundig (using the leccy ariel wire) to a Sony with dedicated amp wire.

The headunit in my mates car is a Goodmans thing so it only has the leccy ariel wire to switch the amp on.

Thing is, will it do any damage to the sub?

[placey]

the thumping might yes. it's an uncontrolled signal being fed to the driver. unlikely granted but possible.

paul

[jmc330i]

it's an uncontrolled signal being fed to the driver.

So is there any way to stop it happening?

[kam-325i]

it's an uncontrolled signal being fed to the driver.

So is there any way to stop it happening?

Not without modifing the head unit (or source of signal). I had same prob with the thump when switching off head unit, but i found out i had two remote switchs, one was norm, one was a delay(Went off before head unit).

[jmc330i]

Ok thanks
Looks like he will just have to put up with it until he gets a new headunit.

[placey]

The headunit didnt have any RCA outputs so I used a converter running off the rear speaker channels

the above holds the answer you're looking for:

as the headunit is shutting down it's sending a signal spike through to your amp - if a head unit has a dedicated amplifier power/accessory signal lead it turns that off before turning itself off hence avoiding the system thump you're experiencing.

way round this is to put a switch in your amplifier remote on lead that's accessible from the drivers seat and use that to turn the amp off before turning off the head unit. i suggest using a heated rear window switch from a scrappy and blacking it as they fit into the dash above the head unit aperture and look factory. (if it's an e30...)

hth - paul

[jmc330i]

Thanks for that Paul

Unfortunately its all in a French car, so theres my mates first mistake
I will let him know about the switch idea and see what he wants to do.

Cheers