bass loud boom when turning off headunit

Hi everyone. this is my 1st post. hope im not breaking any rule or doing anything stupid :D This is by far the greatest website about car audio ive seen. ive been reading it for a while now but today i decided to register and see if someone could give me a hand with a problem i have.I did search before posting but honestly couldnt find the words to explain my problem to the search form. I have a monoblock amplifier and a 15' woofer just installed last week. the thing is everytime i turn off the head unit or change the source (radio/aux/cd) the woofer makes a real loud "boom", like if i was playing real loud music. it happens also when i change the volume level from 1 to 0. if i change the EQ settings on the head unit i get this "boom", and actually it is quite uncomfortable. I asked the guy who installed the system and he told me that all monoblock amplifiers behave like that and i just had to get used to it, but Im not buying that. is it true? and if it isnt, is there something I can do to stop the system from making this unwanted boom? Thanks a lot for any information and/or opinion.

Gear? Makes and models, please. Usually, this is caused by cheap equipment, and barring that, the remote lead for the amp COULD be hooked to a switch lead in the dash, rather than the remote lead on the deck. ...but no, it ISN'T the way ANY decent monoblock behaves.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

According to my Crystal Ball, he has a Pioneer Deck. If this is the case, you need to perform the test in the first paragraph on This Page. If your radio does not show continuity between the RCA shields and the case of the radio, read on and repair it as stated. If you wish to take the radio apart and make the repair inside of the unit, I can help you with that. If it is not a Pioneer deck, there is a problem with the muting circuit of your deck. On what number is the volume of the deck at normal listening levels?

oh soorry about not posting the details before. i was in a hurry last night. thanks for your responses. the head unit is in fact a pioneer. Im gonna do the test you provide in that link "im an idiot" today and see if that is the problem. Ill post back later. thanks a lot.

ok i did the test on that link and my head unit doesn't seem to have that problem. there is continuity between the case and the RCA shields. and the resistance is about half ohm. I have two amplifiers connected, the monoblock and a regular one. what i did now was switching the RCA connections, I connected the monoblock on the other RCA output and the regular amplifier on the sub woofer output and the "boom" on the woofer was gone! but i had this horrible noise on the speakers connected to the regular amplifier. so i know this noise is coming out of the sub woofer RCA output from the head unit. I think I'm gonna take the head unit to be professionally repaired, unless there is something I can do about it? Thanks a lot, and sorry about my bad English. is not my language :D

i am an idiot wrote: Your radio has the problem.  You may have 4 jacks mounted to the back panel of the radio and a separate pigtail with only 2 jacks on that pigtail.  You need to check one of the 4 and one of the 2 on the pigtail.  One set HAS the problem. This will be a very easy repair for you to perform yourself, I will be happy to help you with it.  You will have to remove no more than 5 screws from the unit to be able to do this.

Hi, Im sorry, i didnt quite understand what you just said. do you mean my radio has the problem described on the link you gave me before or that my radio has some other problem? what is a "pigtail"? sorry if i didnt gave enough information before. my head unit is a pioneer Dehp-4850MP. I has 4 RCA jacks on the back. the "regular" is connected to the full range amplifier with 4 coaxial speakers. the sub woofer rca output (labeled "sw" on the back of the radio) is connected the the monoblock amplifier with a 15 inch l5 kicker woofer.

I was just googling for pioneer rca fixes and found this http://www.icixsound.com/vb/showthread.php?t=40067 would that work?

i am an idiot wrote: You need to check all 4 of the jacks.  If they are OK, you have a defective RCA cable.  That fix you posted should take care of the noise,

Well ive checked all 4 jacks and they seem to be ok. I dont think the problem is the RCA cable since i connected both amps to the "noisy" RCA output using each one of the 2 cables and the noise allways comes from the SW output of the head unit. I tried that fix but it actually added noise the the system. really weird.