"thump" from the sub when i turn the HU on...?

[RichieB75]

Hi all, somthing odd started to happen, when i turn my HU on i now get a real "thump" from the sub.

Dosn't matter what level the sound is at, even turned to 0 or paused i always get a big ole thump from the sub, never used to do it :0)

Any ideas?

Btw: its a Vibe 12" black air box with the amp fitted to the box, connected via a quick plug so i can take it out easy. Alpine HU.

[rk696]

Does the sub power off when you turn the HU off? It may be that the remote output on teh HU is giving out power permanently for some reason..

[RichieB75]

yarp, had a look at the connections to make sure everything is ok, the amp powers down about 10 or so seconds after turning the HU off, guess thats the capacitors.

If i turn the HU on after the car has been sat all night then it thumps, and also if i turn off and then straight back on it does it too.

[rk696]

Does it still do it if you disconnect the phono leads from the back of the HU? Could be a problem with the soft start circuit in the amp.

[RichieB75]

Does it still do it if you disconnect the phono leads from the back of the HU? Could be a problem with the soft start circuit in the amp.

ahh didnt try that, i'll try it in the morning when i go to work.

EDIT: ok i turned the gain down a little and it seems ok now, tried removing the RCA but didnt change it. As i understand it the gain affects the incoming signal from the RCA leads?

Edited 19 August, 2010 by RichieB75