head unit turn-on/off thump

[[email protected]]

Hi all,
I've read many topis re: the subject, but none seem to help in my case.

I have a Rockford fosgate amp hooked up to a factory head unit that i
want to keep. The amp turns on/off by itself quietly, but when I hook
up the head unit, it make several 'thumps' or 'pops' when turned on,
and also one wehen turned off.

I'm sure these are caused by the head unit, since when I disconnect it,
everything works fine. There are no other components used (eq's etc)

While trying to locate the problem, I also noticed somthing that could
be related - I get sound from the head unit by connecting the amp with
just one wire! To be specific, since I'm using speaker outputs from the
car cd player and high-level-inputs on the amp, I run (+) and (-) wires
for each channel. When testing, I disconnected all wires going from the
head unit to the amp. If I connect only one (doesn't matter which one)
I start to hear sound from that channel already... When I connect both,
the sound gets about twice as loud. How is this possible?
The head unit had 2 wires running to each of the original speakers, so
they weren't grounded to the chassis for sure. I replaced the speakers,
and made sure the're not shorted anywhere.

Now I'm thinking of using line level converter to transform the car cd
player output and use RCA jack on the amp... Will this help at all? Any
other thoughts how to get rid of the thump?

[keith]

I'll have to think about this one for a bit, but first, make sure that
your HU ground is solid. Consider running it directly to the frame (as
short a runn as possible), and make sure you sand the paint at that
point down to bare metal.

If you've already done that, try the harness ground wire. Given the
discription of the situation, it sounds like there's a ground issue
somewhere... I'm just not sure if it's more likely to be the HU or amp -
so check both.

KeithS



wrote:

> Hi all,
> I've read many topis re: the subject, but none seem to help in my case.
>
> I have a Rockford fosgate amp hooked up to a factory head unit that i
> want to keep. The amp turns on/off by itself quietly, but when I hook
> up the head unit, it make several 'thumps' or 'pops' when turned on,
> and also one wehen turned off.
>
> I'm sure these are caused by the head unit, since when I disconnect it,
> everything works fine. There are no other components used (eq's etc)
>
> While trying to locate the problem, I also noticed somthing that could
> be related - I get sound from the head unit by connecting the amp with
> just one wire! To be specific, since I'm using speaker outputs from the
> car cd player and high-level-inputs on the amp, I run (+) and (-) wires
> for each channel. When testing, I disconnected all wires going from the
> head unit to the amp. If I connect only one (doesn't matter which one)
> I start to hear sound from that channel already... When I connect both,
> the sound gets about twice as loud. How is this possible?
> The head unit had 2 wires running to each of the original speakers, so
> they weren't grounded to the chassis for sure. I replaced the speakers,
> and made sure the're not shorted anywhere.
>
> Now I'm thinking of using line level converter to transform the car cd
> player output and use RCA jack on the amp... Will this help at all? Any
> other thoughts how to get rid of the thump?
>

[[email protected]]

Thanks keith,
I've check the amo ground with a multimeter, so HU ground problem might
be a good clue... Should I disconnect the HU ground wire from the
harness and ground to car chassis or just ground the HU chassis to car
frame?

cheers,
loni

keith wrote:
> I'll have to think about this one for a bit, but first, make sure that
> your HU ground is solid. Consider running it directly to the frame (as
> short a runn as possible), and make sure you sand the paint at that
> point down to bare metal.
>
> If you've already done that, try the harness ground wire. Given the
> discription of the situation, it sounds like there's a ground issue
> somewhere... I'm just not sure if it's more likely to be the HU or amp -
> so check both.
>
> KeithS
>
>

[keith]

I usually run my ground cables from the HU straight to the frame - or
closest convenient piece of metal that's connected to the frame...

Just out of curiosity, if you hook speakers directly to the Hu, does it
still pop? if so, then it's for sure the HU. If not, than you'll need to
reassess. It could also be an issue with the hi-volt input in the amp -
ie, improper downstepping of amperage leading to de-regulation of signal
delivery. You're right in considering a high-low level converter as the
next step in this case.

When you say you checked the amp ground with a MM, did you check for
resistance or continuity? It makes a difference. There can be
continuity, but high resistance values if it isn't a clean ground.

KeithS





wrote:

> Thanks keith,
> I've check the amo ground with a multimeter, so HU ground problem might
> be a good clue... Should I disconnect the HU ground wire from the
> harness and ground to car chassis or just ground the HU chassis to car
> frame?
>
> cheers,
> loni
>
> keith wrote:
>
>>I'll have to think about this one for a bit, but first, make sure that
>>your HU ground is solid. Consider running it directly to the frame (as
>>short a runn as possible), and make sure you sand the paint at that
>>point down to bare metal.
>>
>>If you've already done that, try the harness ground wire. Given the
>>discription of the situation, it sounds like there's a ground issue
>>somewhere... I'm just not sure if it's more likely to be the HU or amp -
>>so check both.
>>
>>KeithS
>>
>>
>
>

[winkenstein]

i had this problem a long time ago (way back in 95? in my '88 T-Bird
T/C)
and it was resolved by running a simple relay in line with the amp turn
on lead.
it was a simple 5 dollar fix
and it still worked perfectly 4 years later when i got rid of the car.
i do not know if it will work for you,
but all i can say is that it worked for me.

(damn! I could kick myself to this very day for getting rid of that
car, I loved it so much!)

[winkenstein]

i had this problem a long time ago (way back in 95? in my '88 T-Bird
T/C)
and it was resolved by running a simple relay in line with the amp turn

on lead.
it was a simple 5 dollar fix
and it still worked perfectly 4 years later when i got rid of the car.
i do not know if it will work for you,
but all i can say is that it worked for me.
(damn! I could kick myself to this very day for getting rid of that
car, I loved it so much!)


ohh, and yes, i, in my opinion would suggest running a high input to
RCA converter.
but that's just my opinion.

but... according to B.W., my opinion sucks, an everything about me is
$h!t, plus
no one should ever listen to me, and the crap i have to say.
so do what ever. you want, dude, i'll just shut up now.
my opinion doesn't matter according to the KING of this place. MR. B.W.
;)

[[email protected]]

relay on a turn on lead? i assume to delay the amp to start only after
the HU is on?
I thought of that, but that won't solve the actual pop, only mute it,
and will not help with turn off pop. But if nothing else works, I might
end up with this...

winkenstein wrote:
> i had this problem a long time ago (way back in 95? in my '88 T-Bird
> T/C)
> and it was resolved by running a simple relay in line with the amp turn
> on lead.

[[email protected]]

That's the strange thing, if i connect speakers directly to HU, there
are no pops whatsover. When the amp is hooked up in their place, I've
gotten as many as 5 pops when turned on. is sounds like if the polarity
would be getting reversed, and i can see the sub going all the way back
and forth.
I've check the resistance of amp ground and was like 0,02ohms, so that
seems OK.
I'll try to get the LLC and play around with the HU ground and see if
that helps.

keith wrote:
> I usually run my ground cables from the HU straight to the frame - or
> closest convenient piece of metal that's connected to the frame...
>
> Just out of curiosity, if you hook speakers directly to the Hu, does it
> still pop? if so, then it's for sure the HU. If not, than you'll need to
> reassess. It could also be an issue with the hi-volt input in the amp -
> ie, improper downstepping of amperage leading to de-regulation of signal
> delivery. You're right in considering a high-low level converter as the
> next step in this case.
>
> When you say you checked the amp ground with a MM, did you check for
> resistance or continuity? It makes a difference. There can be
> continuity, but high resistance values if it isn't a clean ground.
>
> KeithS
>
>
>
>
>
> wrote:
>
> > Thanks keith,
> > I've check the amo ground with a multimeter, so HU ground problem might
> > be a good clue... Should I disconnect the HU ground wire from the
> > harness and ground to car chassis or just ground the HU chassis to car
> > frame?
> >
> > cheers,
> > loni
> >
> > keith wrote:
> >
> >>I'll have to think about this one for a bit, but first, make sure that
> >>your HU ground is solid. Consider running it directly to the frame (as
> >>short a runn as possible), and make sure you sand the paint at that
> >>point down to bare metal.
> >>
> >>If you've already done that, try the harness ground wire. Given the
> >>discription of the situation, it sounds like there's a ground issue
> >>somewhere... I'm just not sure if it's more likely to be the HU or amp -
> >>so check both.
> >>
> >>KeithS
> >>
> >>
> >
> >

[winkenstein]

wrote:
> relay on a turn on lead? i assume to delay the amp to start only after
> the HU is on?
> I thought of that, but that won't solve the actual pop, only mute it,
> and will not help with turn off pop. But if nothing else works, I might
> end up with this...




yep exactly, a slight delay in the turn on time.
and as for the turn off pop,
you are correct, it won't help with that,
sorry, i guess i didn'r catch the off pop part,
i only noted the turn on part,

see, what did i tell ya :)
he (B.W.) knew what he was talkin' about (cause he's the KING)

[keith]

OK, it sounds like the problem is almost definitely with your amp. If it
were the HU signal being delivered, the speakers would pop from that
too. Hook up the LLC and see what happens. Also, 0.02 Ohms is good (as
long as it's not kOhms!)

KeithS

wrote:

> That's the strange thing, if i connect speakers directly to HU, there
> are no pops whatsover. When the amp is hooked up in their place, I've
> gotten as many as 5 pops when turned on. is sounds like if the polarity
> would be getting reversed, and i can see the sub going all the way back
> and forth.
> I've check the resistance of amp ground and was like 0,02ohms, so that
> seems OK.
> I'll try to get the LLC and play around with the HU ground and see if
> that helps.
>
> keith wrote:
>
>>I usually run my ground cables from the HU straight to the frame - or
>>closest convenient piece of metal that's connected to the frame...
>>
>>Just out of curiosity, if you hook speakers directly to the Hu, does it
>>still pop? if so, then it's for sure the HU. If not, than you'll need to
>>reassess. It could also be an issue with the hi-volt input in the amp -
>>ie, improper downstepping of amperage leading to de-regulation of signal
>>delivery. You're right in considering a high-low level converter as the
>>next step in this case.
>>
>>When you say you checked the amp ground with a MM, did you check for
>>resistance or continuity? It makes a difference. There can be
>>continuity, but high resistance values if it isn't a clean ground.
>>
>>KeithS
>>
>>
>>
>>
>>
wrote:
>>
>>
>>>Thanks keith,
>>>I've check the amo ground with a multimeter, so HU ground problem might
>>>be a good clue... Should I disconnect the HU ground wire from the
>>>harness and ground to car chassis or just ground the HU chassis to car
>>>frame?
>>>
>>>cheers,
>>>loni
>>>
>>>keith wrote:
>>>
>>>
>>>>I'll have to think about this one for a bit, but first, make sure that
>>>>your HU ground is solid. Consider running it directly to the frame (as
>>>>short a runn as possible), and make sure you sand the paint at that
>>>>point down to bare metal.
>>>>
>>>>If you've already done that, try the harness ground wire. Given the
>>>>discription of the situation, it sounds like there's a ground issue
>>>>somewhere... I'm just not sure if it's more likely to be the HU or amp -
>>>>so check both.
>>>>
>>>>KeithS
>>>>
>>>>
>>>
>>>
>

[MOSFET]

I had a problem SIMILAR to yours once (but I wasn't using speaker-level
inputs from a HU, I was using line-level inputs). I fixed it by reversing
the polarity of one of the RCA inputs to the subwoofer amp.

You may have already tried this, but I would DEFINITELY try reversing the
polarity of one of the inputs because it does sound like some kind of
phasing issue. This may be a shot in the dark, but it's worth a try.

If that doesn't work, Winkenstein's relay idea should take care of the
problem.

MOSFET

> wrote in message
oups.com...
> Hi all,
> I've read many topis re: the subject, but none seem to help in my case.
>
> I have a Rockford fosgate amp hooked up to a factory head unit that i
> want to keep. The amp turns on/off by itself quietly, but when I hook
> up the head unit, it make several 'thumps' or 'pops' when turned on,
> and also one wehen turned off.
>
> I'm sure these are caused by the head unit, since when I disconnect it,
> everything works fine. There are no other components used (eq's etc)
>
> While trying to locate the problem, I also noticed somthing that could
> be related - I get sound from the head unit by connecting the amp with
> just one wire! To be specific, since I'm using speaker outputs from the
> car cd player and high-level-inputs on the amp, I run (+) and (-) wires
> for each channel. When testing, I disconnected all wires going from the
> head unit to the amp. If I connect only one (doesn't matter which one)
> I start to hear sound from that channel already... When I connect both,
> the sound gets about twice as loud. How is this possible?
> The head unit had 2 wires running to each of the original speakers, so
> they weren't grounded to the chassis for sure. I replaced the speakers,
> and made sure the're not shorted anywhere.
>
> Now I'm thinking of using line level converter to transform the car cd
> player output and use RCA jack on the amp... Will this help at all? Any
> other thoughts how to get rid of the thump?
>

[[email protected]]

So here's the news. I played with the install over the weekend, and
when I hooked up the LLC, the thump went away! Hooray! Well, to speak
the truth it didn't disappear completely, but it's now barely audible.
About as loud as the actual click a button on the HU makes when you
press it... Still there but certainly a HUGE improvement, and fine with
me.
I also found out that the sound coming from my amp with only (+) lead
of channel connected to the HU stops when I unplug the antenna from the
HU. I assume this has something to do with a weak/wrong grounding.
Again, not an issue when all leads hooked up, but I'll see if I can fix
this also by grounding the antenna and/or the HU properly.

Thanks to all those who helped so far...
ML

keith wrote:
> OK, it sounds like the problem is almost definitely with your amp. If it
> were the HU signal being delivered, the speakers would pop from that
> too. Hook up the LLC and see what happens. Also, 0.02 Ohms is good (as
> long as it's not kOhms!)
>
> KeithS
>
> wrote:
>
> > That's the strange thing, if i connect speakers directly to HU, there
> > are no pops whatsover. When the amp is hooked up in their place, I've
> > gotten as many as 5 pops when turned on. is sounds like if the polarity
> > would be getting reversed, and i can see the sub going all the way back
> > and forth.
> > I've check the resistance of amp ground and was like 0,02ohms, so that
> > seems OK.
> > I'll try to get the LLC and play around with the HU ground and see if
> > that helps.
> >
> > keith wrote:
> >
> >>I usually run my ground cables from the HU straight to the frame - or
> >>closest convenient piece of metal that's connected to the frame...
> >>
> >>Just out of curiosity, if you hook speakers directly to the Hu, does it
> >>still pop? if so, then it's for sure the HU. If not, than you'll need to
> >>reassess. It could also be an issue with the hi-volt input in the amp -
> >>ie, improper downstepping of amperage leading to de-regulation of signal
> >>delivery. You're right in considering a high-low level converter as the
> >>next step in this case.
> >>
> >>When you say you checked the amp ground with a MM, did you check for
> >>resistance or continuity? It makes a difference. There can be
> >>continuity, but high resistance values if it isn't a clean ground.
> >>
> >>KeithS
> >>
> >>
> >>
> >>
> >>
> wrote:
> >>
> >>
> >>>Thanks keith,
> >>>I've check the amo ground with a multimeter, so HU ground problem might
> >>>be a good clue... Should I disconnect the HU ground wire from the
> >>>harness and ground to car chassis or just ground the HU chassis to car
> >>>frame?
> >>>
> >>>cheers,
> >>>loni
> >>>
> >>>keith wrote:
> >>>
> >>>
> >>>>I'll have to think about this one for a bit, but first, make sure that
> >>>>your HU ground is solid. Consider running it directly to the frame (as
> >>>>short a runn as possible), and make sure you sand the paint at that
> >>>>point down to bare metal.
> >>>>
> >>>>If you've already done that, try the harness ground wire. Given the
> >>>>discription of the situation, it sounds like there's a ground issue
> >>>>somewhere... I'm just not sure if it's more likely to be the HU or amp -
> >>>>so check both.
> >>>>
> >>>>KeithS
> >>>>
> >>>>
> >>>
> >>>
> >