Turn Off Thump

[Tony F]

One thing I've noticed since I got my new CD player is that whenever I turn
off the car's ignition there is a thump, or snapping sound out of my
speakers. Anyway, this is the first time I've experienced this. I can
assume that this is not common since it's never happened to me before. 1)
What exactly might be causing it? 2) How might I stop it? 3) Is it bad for
my speakers?

Tony


--
2001 Nissan Maxima SE Anniversary Edition
Clarion DRZ9255 Head Unit, Phoenix Gold ZX475ti, ZX450 and Xenon X1200.1
Amplifiers, Dynaudio System 360 Tri-Amped In Front and Focal 130HCs For Rear
Fill, Image Dynamics IDMAX10 D4 v.3 Sub

2001 Chevy S10 ZR2
Pioneer DEH-P9600MP Head Unit, Phoenix Gold Ti500.4 Amp, Focal 165HC
Speakers & Image Dynamics ID8 D4 v.3 Sub

[Ian]

On Tue, 04 Oct 2005 01:36:16 GMT, Tony F wrote:

> One thing I've noticed since I got my new CD player is that
> whenever I turn off the car's ignition there is a thump, or
> snapping sound out of my speakers. Anyway, this is the
> first time I've experienced this. I can assume that this
> is not common since it's never happened to me before. 1)
> What exactly might be causing it? 2) How might I stop it?
> 3) Is it bad for my speakers?

I read that this is a good thing. The "thump" sound is the sound
of the amp's capacitors discharging. Read about it yourself at:

http://stereos.about.com/cs/audiofaq/f/amp_thump.htm

[MZ]

> > One thing I've noticed since I got my new CD player is that
> > whenever I turn off the car's ignition there is a thump, or
> > snapping sound out of my speakers. Anyway, this is the
> > first time I've experienced this. I can assume that this
> > is not common since it's never happened to me before. 1)
> > What exactly might be causing it? 2) How might I stop it?
> > 3) Is it bad for my speakers?
>
> I read that this is a good thing. The "thump" sound is the sound
> of the amp's capacitors discharging. Read about it yourself at:
>
> http://stereos.about.com/cs/audiofaq/f/amp_thump.htm

Wow, that website is way off...

[Tony F]

"I read that this is a good thing. The "thump" sound is the sound of the
amp's capacitors discharging. Read about it yourself at:

http://stereos.about.com/cs/audiofaq/f/amp_thump.htm"

Thanks, Ian.

Mark...other than the site "being way off" what can you tell me about my
problem? And what would a HU have to do with this? It never ever happened
until I got my Clarion.

Tony


--
2001 Nissan Maxima SE Anniversary Edition
Clarion DRZ9255 Head Unit, Phoenix Gold ZX475ti, ZX450 and Xenon X1200.1
Amplifiers, Dynaudio System 360 Tri-Amped In Front and Focal 130HCs For Rear
Fill, Image Dynamics IDMAX10 D4 v.3 Sub

2001 Chevy S10 ZR2
Pioneer DEH-P9600MP Head Unit, Phoenix Gold Ti500.4 Amp, Focal 165HC
Speakers & Image Dynamics ID8 D4 v.3 Sub

[MZ]

> "I read that this is a good thing. The "thump" sound is the sound of the
> amp's capacitors discharging. Read about it yourself at:
>
> http://stereos.about.com/cs/audiofaq/f/amp_thump.htm"
>
> Thanks, Ian.
>
> Mark...other than the site "being way off" what can you tell me about my
> problem? And what would a HU have to do with this? It never ever happened
> until I got my Clarion.

Oftentimes, the turn off thump is simply related to the amplifier not
turning off at the right time relative to when the HU turns off. Isn't
this one in the FAQ?

[Bruce Chang]

"MZ" > wrote in message
...
>> "I read that this is a good thing. The "thump" sound is the sound of the
>> amp's capacitors discharging. Read about it yourself at:
>>
>> http://stereos.about.com/cs/audiofaq/f/amp_thump.htm"
>>
>> Thanks, Ian.
>>
>> Mark...other than the site "being way off" what can you tell me about my
>> problem? And what would a HU have to do with this? It never ever
>> happened
>> until I got my Clarion.
>
> Oftentimes, the turn off thump is simply related to the amplifier not
> turning off at the right time relative to when the HU turns off. Isn't
> this one in the FAQ?

I used to get this all the time when I first got my firebird. Turns out the
previous owner had hooked up the amp so it was on ALL the time, not just
when the ignition was on.

-Bruce

[Matt Ion]

Tony F wrote:
> "I read that this is a good thing. The "thump" sound is the sound of the
> amp's capacitors discharging. Read about it yourself at:
>
> http://stereos.about.com/cs/audiofaq/f/amp_thump.htm"
>
> Thanks, Ian.
>
> Mark...other than the site "being way off" what can you tell me about my
> problem? And what would a HU have to do with this? It never ever happened
> until I got my Clarion.

Well first of all, energy is not rated in Farads, so a capacitor cannot
store "microfarads ... of electrical power". The way he writes it, he
makes it sound as if Farads and Joules are both measuring the same
thing, and a Joule is the equivalent to "several tousands of
microfarads". The Farad is a measurement of capacitance; a Joule is a
measurement of energy (not necessarily electrical).

More relevant to the discussion, the "thump" is more likely caused by
the HU shutting down before the amp, and the resulting output "click"
being amplified into a "thump".


---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 0540-1, 10/04/2005
Tested on: 10/4/2005 4:59:59 PM
avast! - copyright (c) 1988-2005 ALWIL Software.
http://www.avast.com

[Tony F]

"Oftentimes, the turn off thump is simply related to the amplifier not
turning off at the right time relative to when the HU turns off. Isn't this
one in the FAQ?"

It probably is, Mark. Problem is that I've been a regular on this newsgroup
long enough that when I do ask a question, it's more complex than most found
on the FAQ. And when I do ask a simple question, I forget to consult the
FAQ first.

In conclusion...I think I'm at that point that I know just enough to really
get myself into trouble.

Tony


--
2001 Nissan Maxima SE Anniversary Edition
Clarion DRZ9255 Head Unit, Phoenix Gold ZX475ti, ZX450 and Xenon X1200.1
Amplifiers, Dynaudio System 360 Tri-Amped In Front and Focal 130HCs For Rear
Fill, Image Dynamics IDMAX10 D4 v.3 Sub

2001 Chevy S10 ZR2
Pioneer DEH-P9600MP Head Unit, Phoenix Gold Ti500.4 Amp, Focal 165HC
Speakers & Image Dynamics ID8 D4 v.3 Sub

[MZ]

> In conclusion...I think I'm at that point that I know just enough to really
> get myself into trouble.

If getting yourself into trouble is the main criteria, then you're at
what's called the most advanced stage. :)

[[email protected]]

How much you spent on your head system?

[MZ]

On Wed, 5 Oct 2005 wrote:

Oh god, not this again. I'm not sure I can handle both this guy and bob
at the same time...

[Chad Wahls]

"MZ" > wrote in message
...
>> "I read that this is a good thing. The "thump" sound is the sound of the
>> amp's capacitors discharging. Read about it yourself at:
>>
>> http://stereos.about.com/cs/audiofaq/f/amp_thump.htm"
>>
>> Thanks, Ian.
>>
>> Mark...other than the site "being way off" what can you tell me about my
>> problem? And what would a HU have to do with this? It never ever
>> happened
>> until I got my Clarion.
>
> Oftentimes, the turn off thump is simply related to the amplifier not
> turning off at the right time relative to when the HU turns off. Isn't
> this one in the FAQ?

Turn ON thump is a somewhat easy fix by delaying the remote turn on until
the outputs of the head unit stabilize.

Turn OFF thump occurs when the amplifier does it's job for the split second
that the output circuitry of the headunit or preceding equipment becomes
unstable due to voltage drop from power down. I have actually upgraded caps
on the rails of the op amps in head units and processors to hold them
operating while the amp shuts off.. Many times I see the problem in
(believe it or not) upper end units that have a differential power supply,
if one side (positive or negative voltage) falls faster than the other than
the op-amp can produce some DC offset, as the DC voltage rises then the amp
shuts off the sudden cone movement of the speaker causes an audible pop or
thump. This often happens so fast as to not trigger the amp's DC protection
and sometimes it does trigger so fast that it's not noticed.

Dealing with turn off thump is a sort of manipulation of the time-space
continuum because it's tough to turn off the amp before the headunit, if ya
know what I mean :)

Confronting the problem sometimes involves more time and equipment than the
average home-garage installer is willing forth.

The first step is determining what the amp is doing and if the inputs and
outputs are still active until the amp's power supply discharges. The
remote turn on function of an amplifier is rarely a relay and rarely do I
see relays on speaker outputs, the amplifier is activated and deactivated
buy turning on and off the switching circuitry that drives the power supply
FETs. True, an amp that has good power supply filtering will remain active
until the caps deplete, the low voltage side will almost always deplete
first. Many amps incorporate what's called muting FETs right at the input,
this is a transistor that is tied between the ground and signal and when
energized has a high impedance between this junction, when not energized it
is nearly a dead short. These are tied to the remote circuitry and not
filtered. When the remote signal is lost these quickly dump the signal to
ground via a resistor and mute the inputs to the amp. Many head units also
have this arrangement and mute the outputs the split second the unit senses
a turn off command and often times while switching functions (CD,Radio, Aux)
Sometimes they are often triggers even by the zero bit detector in the DAC.
so when you are switching tracks... the output is muted.

Now find out what in the signal chain is staying on long enough to amplify
this thump. Logic says start with the power amplifier. First, unhook the
signal inputs but nothing else, turn the system on and off, does the thump
occur? If so, blame the amp, it should not do this, get it repaired or
replace it. Often times aging electrolytic caps in an amp can cause this in
older models. If it does not occur then it's time to drag out test
equipment. On a scope (preferably a storage scope) observe the turn on
signal (remote) on one channel and on the other channel the output of the
amplifier as the amp being driven directly by a signal generator at low
volume. Turn off the system and observe the time difference between the
loss of remote signal and how long the amp still plays. If it play's out
for more than a cycle of a waveform then it has no muting FETs on the
inputs You can homebrew a box with these fets that will have signal in and
out and a remote trigger. I also believe these are made available pre
fabbed. This should solve your thump problem as long as the devices in
parallel with the remote turn on are un filtered. A cap in parallel with
the remote turn on will hold it active longer. So crossovers, EQ's,
anything with a remote input COULD be holding it high. If this is the case
you will see the output end when the remote come down but still have a
thump. In other words the headunit says it's time to shut off but in all
actualy the "remoted" gear shuts off later due a charge on the remote line,
the head unit THINKS it's off. This is also a common problem. Try
disconnecting the remote input to auxiliary gear and running the headunit
outputs right to the amp, does the thump still occur? If not the remote
input is being held high and the "remoted" gear is not being shut off fast
enough. The remote input on this equipment has a VERY high input impedance,
sometimes remote inputs are filtered to reduce the problems with sudden
voltage inconsistencies. Sometime a simple bleeder resistor from ground to
the remote turn on will bleed out the turn on voltage fast enough to prevent
thumps, Do calculate the maximum current that can be delivered by the remote
output of the head unit and DO NOT exceed this by installing a dropping
resistor. I have found that a 1K1/2W resistor often does the trick of
pulling this signal down quickly and causes little/no effect on the headunit
remote output in terms of operating voltage drop. This resistor can be
placed anywhere in the remote chain, I prefer the amp but it's all up to
aesthetics!

There are sooo many other things but I'm running out of free time! Tony,
this is my valid E-mail address don't be afraid to contact me with your
findings or post up here so we can all attack it!

[[email protected]]

Why not? I'm here to help other.

[Les]

Hmmm, I think they may be the same. Never know, could be at work and home.
Then again it could be Jeffery Julian Demarco's alternate personality too.


"MZ" > wrote in message
...
> On Wed, 5 Oct 2005 wrote:
>
> Oh god, not this again. I'm not sure I can handle both this guy and bob
> at the same time...

[mm]

On Tue, 04 Oct 2005 22:24:21 GMT, "Bruce Chang"
> wrote:

>
>I used to get this all the time when I first got my firebird. Turns out the
>previous owner had hooked up the amp so it was on ALL the time, not just
>when the ignition was on.
>
>-Bruce

In my '67 Pontiac, the factory, original equipment reverberator was on
all the time the engine was running, not just when the radio was on.

I had the car for several months before I noticed this, partly because
the radio was always on. But one time I was alone in the car, and it
was quiet and I was thinking, and although the bump didn't seem so
big, maybe smaller than other bumps, the speaker belted out a big
vibrating gong, and scared me to death.


And it took me a while to figure out what the noise was.

Remove NOPSAM to email me. Please let
me know if you have posted also.

[Vivek]

Your ignorance is required, not handling

--
The best is yet to come
V


"MZ" > wrote in message
...
> On Wed, 5 Oct 2005 wrote:
>
> Oh god, not this again. I'm not sure I can handle both this guy and bob
> at the same time...

[Bruce Chang]

"mm" > wrote in message
...
> On Tue, 04 Oct 2005 22:24:21 GMT, "Bruce Chang"
> > wrote:
>
>>
>>I used to get this all the time when I first got my firebird. Turns out
>>the
>>previous owner had hooked up the amp so it was on ALL the time, not just
>>when the ignition was on.
>>
>>-Bruce
>
> In my '67 Pontiac, the factory, original equipment reverberator was on
> all the time the engine was running, not just when the radio was on.
>
> I had the car for several months before I noticed this, partly because
> the radio was always on. But one time I was alone in the car, and it
> was quiet and I was thinking, and although the bump didn't seem so
> big, maybe smaller than other bumps, the speaker belted out a big
> vibrating gong, and scared me to death.
>
>

Does this mean you're posting this from beyond the grave? =oS

[Scott Gardner]

On Wed, 05 Oct 2005 08:20:06 GMT, MZ > wrote:

>On Wed, 5 Oct 2005 wrote:
>
>Oh god, not this again. I'm not sure I can handle both this guy and bob
>at the same time...

Now all we need is to have Spockie come back...

--
Scott Gardner

"Fighter pilots make movies, bomber pilots make history....But Hawkeye bubbas write the scripts."

[mm]

On Thu, 06 Oct 2005 19:29:55 GMT, "Bruce Chang"
> wrote:

>
>"mm" > wrote in message
...
>> On Tue, 04 Oct 2005 22:24:21 GMT, "Bruce Chang"
>> > wrote:
>>
>>>
>>>I used to get this all the time when I first got my firebird. Turns out
>>>the
>>>previous owner had hooked up the amp so it was on ALL the time, not just
>>>when the ignition was on.
>>>
>>>-Bruce
>>
>> In my '67 Pontiac, the factory, original equipment reverberator was on
>> all the time the engine was running, not just when the radio was on.
>>
>> I had the car for several months before I noticed this, partly because
>> the radio was always on. But one time I was alone in the car, and it
>> was quiet and I was thinking, and although the bump didn't seem so
>> big, maybe smaller than other bumps, the speaker belted out a big
>> vibrating gong, and scared me to death.
>>
>>
>
>Does this mean you're posting this from beyond the grave? =oS

I have wireless internet up here. It's my only communication with
earth.


Remove NOPSAM to email me. Please let
me know if you have posted also.

[mm]

On Mon, 3 Oct 2005 18:36:16 -0700, "Tony F"
> wrote:

>One thing I've noticed since I got my new CD player is that whenever I turn
>off the car's ignition there is a thump, or snapping sound out of my
>speakers. Anyway, this is the first time I've experienced this. I can
>assume that this is not common since it's never happened to me before.

You can assume that, but I wouldn't. There are hundreds of millions
of car radios in the world, a


1)
>What exactly might be causing it? 2) How might I stop it? 3) Is it bad for
>my speakers?
>
>Tony


Remove NOPSAM to email me. Please let
me know if you have posted also.