It's not really that the fuse itself is overrated, it's that sometimes
amps have larger fuses than they need, so it's not accurate to use
fuse size to estimate the RMS power of an amplifier. After all,
there's nothing to keep a manufacturer from putting a 30-amp fuse on a
100W amplifier.

When you calculated 195 WRMS for your amplifier based on the 30-amp
fuse it uses, all that means is that the amp can produce AT MOST about
195 WRMS. There's no way to tell from the fuse how much the amp
*really* puts out, only that it's less than or equal to about 195
WRMS. It might be 195 WRMS, or it might be 125 WRMS or even less.

Scott Gardner



On 25 May 2004 10:35:33 -0700, (charlie) wrote:

whatt how can a fuse be over rated? its a 30 amp automotive fuse, not
even made by pyramid. i bought it at autozone. and also somone was
talking about my watts per dollar discussion and how people look for
other factors suckh as reliability and looks. well so far ive used the
hell out of this thing for over a year, and i have yet to have any
proplems with it. it works great. ad as far as looks it looks pretty
cool. here is a link of what it looks like.
http://www.etronics.com/product.asp?...ore=&catid=308



Kevin McMurtrie wrote in message ...
You just explained in great detail why people hate Pyramid. They lie
out their asses about their product specifications.

So your fuse allows for your "1000W" amp to put out up to 200W. How do
you know that the fuse isn't over rated too? Real 200W RMS amps are a
dime a dozen. There's nothing hard about making one. I even built a
180W RMS car amp from scratch while I was in High School.

I would like everybody to explain to me why caps are BS.... i am an
electrical engineer... I know what a cap does and if you think these
caps
cannot help you then you are mistaken.


I am ACTUALLY an EE and get paid to be one! But, I'll let the non EE's
have
at you. Being an EE I am reluctant to admit it on the net, I prefer to
claim to be a bridge welder, or professional world saving action hero. It
sounds soooo much more exciting.

There are other folks in here that are EEs but don't feel the need to point
that out, and instead let the posts speak for themselves.

And then there are some people in here that are not formally trained as EEs
but know more than us anyway.

"MZ" wrote in message
...
And then there are some people in here that are not formally trained as
EEs
but know more than us anyway.



These are the ones I respect the most!
Chad

Ok thanks for the post.. i understand why people think caps are
bs... i get it now... im not fimilar with the interior working of an amp..
for example i sure as heck didnt think they used +/- 90V to produce a
sound... i am still sceptical on this point ... however...

I do see now that caps wont help much, what will help is the correct sized
wire run out to the amp.

I would like everybody to explain to me why caps are BS.... i am an
electrical engineer...

Isn't is amazing how everyone is an electrical engineer on the internet?

I really am one... just that my field of study was not specifically into
car audio amplifiers... insted of knocking me why not explain why i am
wrong and show me how to better myself....

I know what a cap does and if you think these caps
cannot help you then you are mistaken.

Read a little further and you will prove that you do not.


I now see that thanks...


When resistance builds up in the wire to the amp or the terminal on the
amp
cannot accept your 4 guage wire so you strip half the copper off... then
guess what your resistance just went up, also resistance goes up when
running cause the wires warm up..

Resistance doesn't "build up"

Resistance does build up in a wire... masure the resistance at start +1 Ft
of wire and you get X (very small resistance) as you move down the wire the
resistance builds up because you keep adding resistance... get it now? I
didnt explain that well enough the first time sorry...

.. Stripping half of the unneeded copper away won't be detrimental.

It sure as heck doesnt help,.,.., if i had 4 guage wire then removed the
copper so that i get a piece of 18 guage coming out of a 4 guage wire...
the 18 guage piece will get hot and go up in resistance... the 18 guage
piece cannot carry the current that is needed to support the amp... people
who run 4 guage wire then cut away the coper to make like 10 guage would
have been better off just running 10 guage... they might get a little
bit more current carraying capibility with the 4 guage to 10 guage.. but not
for the price difference.... Remember electrons flow on the outside of a
copper conductor, stranded wire is better then solid wire...







You said Caps are junk?

You know what a cap is? Its a small version of the batttery under your
hood...

And there goes your EE claim. A small battery would be an example of a
small
version of the one under the hood. Not a cap.

Sorry i didnt explain the reson I said the battery was like a cap is because
the voltagev on a battery cannot change insontainesoley... just like a cap.

You can put another battery right next to the amp i suppose.. then you dont
have to worry about the size of the wire going to the amp and battery from
the alternator.. though the battery will lose its charge quickly if playing
loudly... the alternator has to charge two batteries then...

I suggest just doing it right with no cap and no battery..

I was just wondering before why caps are junk and you anwsered that (Caps
are junk in some cases not all) For example you know you can make your car
headlights last 100 times longer with the use of a cap? What damages
headlights? the change in temperature... so add a cap and the temp wont
change so fast on a head light.



except your battery can be considered many Farads as a cap that is
very expensive may be 1 or 2 farads.

Locating a cap right next to the Amp will help in providing current to
the
amp if it needs it (a cap's voltage cannot cahge instontainusly
(spelling)
it is the properity of a cap)

It will "help" for an insignifigant amount of time.

therefore it will hold its voltage through those large current drawing
bass
hits.

It will only do any good for a brief second. An external cap is not
effective with long current draws.


Agreed... but for the quick burst it can help


Anyway before you try to make me look like an idiot do some research

Why don't you first. A cap is not a battery. The amplifier designers
already
designed the amp with enough capacitance. The voltage drop you speak of is
usually insignifigant. If the voltage drops down to 7-10 volts then your
amps would shut off.
I think we could go on, but I think that's enough to debunk your claim of
being an Electrical Engineer.

Claim or not I know what i am... my area of knoladge does not reside in car
audio... I would like to learn more so please give my ignorance a chance,
ill try to be more understanding in the future... I learned a lot so far
not just from you but many of the others... Thanks...


Ken An EE But college apparently means nothing but a piece of paper.


Les
Not an EE.

"Eddie Runner" wrote in message
...
Mercury wrote:

I would like everybody to explain to me why caps are BS.... i am an
electrical engineer... I know what a cap does and if you think these
caps
cannot help you then you are mistaken.

As a driver of electric trains, you should be smart enough to look this
stuff up.

A cap wont hurt anything, except your wallet cause they aint cheap!
Havin more juice if you need it is a good thing...
But the question is, do you really need it..??

Car Amps have a 12 volt capacitor bank inside them already on the power
wire inputs... Dont the amp manufacturers make this cap bank big enough???
One primary goal of this input cap bank is to prevent the switching of the
amplifiers power supply from feeding back into the cars electrical system.

Understood... I am sure the car has some crap on the 12V rail that can be
considered noisy to the amplifier as well.


Car amps have another cap bank on the power rails after the power supply.
(typicly + and - 40 volts or more)
This is where the juice is stored and ready to use for the output
transistors.

I did not realize it went up that high... I figured maybe 20 volts

This is really where alot of energy should be stored for use.

If I wanted to add a cap where it would seem to be the best, it would be
on the power supply rails not the amp 12 volt input.... Wouldnt it be
better
to store several farads of 90 volts than 12 volts?
First of all a 1F cap is expensive enough at 20 volts... buy one at 90
Volts (it would be huge first of all and prolly cost a grand)

Wouldnt it be bettter to
have the storage right where the juice is ready to be used, or at the amps
inputs
where much could be lost through the bottleneck of the DC - AC - DC
power supply of the amplifier...??

In the early days of car amps many of us experemented with big caps
on the power inputs (mostly as noise filters) and on the power supply
rails
(as storage devices)...

Some one saw what we were doing and decided to
buy a bunch of surplus caps and rebadge them with fold plated terminals
and
then ANYONE could have stuff just like the early PRO competitors used.

Now I like to refer to them as JEWELRY CAPS.....

Most folks that have conducted actuall listening tests have come up with
NO DIFFERENCE..... SO is it worth it?


Ill give you that if the car is wired right (large power wires) to the
amp
then a cap is not needed.

Most cars are OVERWIRED!!!
An amp that would easily work with an 8 gu wire is manytimes wired
with a 4 gu nowdays....

When resistance builds up in the wire to the amp or the terminal on the
amp

How does resistance build up?
Sounds like your saying builds up over time..?? Or as it heat us??
Or as you move along the length of the wire?
Move along the length of the wire.. i was using terms like build up...
sorry i should have made it simplier...


cannot accept your 4 guage wire so you strip half the copper off...

If your talking about striping the wire to put it into a connector that is
acceptable and not a problem... If your en engineer (toot toot) then
you oughta know the wire being thinner for a small time may not be
a hindrence ... your resistance is r1+r2+r3+r4, ... Might be better
to have no connectors at all, but thats not usually possible...And usually
not a problem if they are connected well.

I dare you to push 50 amps (just picking numbers now) through a 4 guage
wire that was reduced to the diamater of a 20 guage wire for 1 inch) guess
what... that small diamater will act like a fuse I assume the same thing
in a car... explain it to me if i am wrong please...


then
guess what your resistance just went up,

resistance goes up on EVERY connector, and every distribution block and
every inch of wire you use.... with R*I you can see what your voltage
loss
is, which for most overbuilt car systems is not much....

PLUS, more to the point, a cap is only storage for a very small period of
time,
it will probably not work as a band aid to bad wireing... So wire it right
and
forget the cap...
Agreed... i had a misconetption about the caps

also resistance goes up when
running cause the wires warm up..


have you ever felt a wire when a car amp was running?
A wellinstalled systen will not cause the wire to get hot enough
to cause any measureable resistance change.

A good system voltage on a car will be well over 13.5V while running

thats the alternator voltage..... Since alot of alternators are not that
beefy,
its pretty common to measure a voltage fluctuation at the amplifier
between
the 13.5 of the wimpy alternator and the 12 volts of the car battery.
This
voltage fluctuation has nothing to do with striping the 4 gu wire wrong,
it
just has to do with an alternator being wimply or old or broken...

A cap could help fill in here, but bass notes are pretty lengthy nowdays
so a cap will still just discharge on a bass note not making a whole lot
of difference in the voltage fluctuation...

AND probably even more important, the measureable voltage fluctuation
that you may measure between alternetor and bettery voltage is not enough
to HEAR anything detrimental through your stereo.... so
1) you cant hear the problem
2) if you cant hear the problem you cant hear the cap even if it fixed the
problem.

So the amp doesnt mind large voltage swings?


Batteries and altinators are not made to handle the large current draws
of
an amplifier (most peak current draw of well over 50A)

betteries sure are!!
Battereis are there to start the car, whch could take well over 50 amps!

guess what.. if
your wire is an ohm you lost 50 volts..

put a 1 ohm resistor on your 12 volt power supply, measure it and even
through
the 1 ohm resistor and you will still see 12 volts! According to your
statement we
would loose 50 volts so I guess your saying we should see -38 volts.... ha
ha ha
Yeah yeah i was picking numbers and was in a rush... quick eyes i like
that...

Even if you have a 50 ohm resistor you will STILL see 12 volts....

remember I*E

For the voltage loss to occur there must be current flow, the more current
the
more loss.... its not JUST the resistance!!! It is both!

Dont tell me that voltage doesnt drop across a wire because I know it
does.

You dont seem to be very well versed on the subject....
Your en electrical engineer, think about those train tracks that go round
and round.

its a simple concept really!

with 4 Guage wire Which is HUGE HUGE you will drop 200mV given you
used
10 ft of 4 guage

NOT TRUE!!!
It depends on the current draw.

I am sorry did you see the link i showed... i think the current i selected
was 50A

now make that 8 guage
you drop .335V

NOT TRUE!!
Again it would depend on the current draw.

Voltage drop calculations must have current and resistance....

I just did a google and one web site says its
4 gu .000292 r per ft
8 gu .000739 r per ft
using these figgures voltage drop is as follows.

start with 14 volts and 15 ft of wire

4gu 14volts - 1amp - 0.00438 drop 14.00 left
8gu 14volts - 1amp - 0.01108 drop 13.99 left
4gu 14volts - 10amp - 0.04380 drop 13.96 left
8gu 14volts - 10amp - 0.11085 drop 13.89 left
4gu 14volts - 25amp - 0.10950 drop 13.89 left
8gu 14volts - 25amp - 0.27712 drop 13.72 left
4gu 14volts - 50amp - 0.21900 drop 13.78 left
8gu 14volts - 50amp - 0.55425 drop 13.45 left
4gu 14volts - 75amp - 0.32850 drop 13.67left
8gu 14volts - 75amp - 0.83137 drop 13.17left
4gu 14volts - 100amp - 0.43800 drop 13.56left
8gu 14volts - 100amp - 1.10850 drop 12.89left
4gu 14volts - 125amp - 0.54750 drop 13.45left
8gu 14volts - 125amp - 1.38562 drop 12.61left

I would a stopped using the 8 gu back around 50 amps
or so, but you see even at 100 amps there is only 1 volt
of current drop, and on music that would only be on the
big bass hits where lots of current flows, not ALWAYS,
so you can see the way we usually build systems is way
overbuilt.... (usually)

I hope you also see how the current dictates the current
drop, as the resistance of the wire and the starting voltage
did not change....

And still the voltage drop with the smallest wire and the
biggest draw is still probably not a problem for most folks,
and the way most cars are overbuilt, the 125 amps on
8 gu is unlikley to be seen..... ;-)


This is at 70 degress F most likely... wire gets derated
substaintially
with heat....

substancially my ass!
it takes lots of heat to change it BARELY!!

next time youre blasting your rap check and see what the
temperature of the wire is... you shouldnt be surprized to find out
that
youre loosing .5 - 1V pretty easily

Whoever gave you your electric train liscense (EE degree) should
be drummed outa the college... He let you miss too many days and
still passed you....

You said Caps are junk?

I said caps are JEWELRY!
Wear em if you like, they cost alot....

Caps have a better purpose in the other world of electtronics.. maybe not as
large cans as proven to me but in digital world they are used all over
the small ceramic ones...

Anyway before you try to make me look like an idiot do some research

you made yourself look like an idiot....
YOU should do some research.....

youre right... and i am ready and prepared to feel the rath of all of you
... and hopefully learn som,ething in the process

Kenny


TOOT TOOT!!!!

Eddie Runner
http://www.installer.com/tech/

Ok thanks for the post.. i understand why people think caps are
bs... i get it now... im not fimilar with the interior working of an
amp..
for example i sure as heck didnt think they used +/- 90V to produce a
sound... i am still sceptical on this point ... however...

I think Eddie said 90v, which would imply +/-45v which is typical for larger
amps.

Resistance doesn't "build up"

Resistance does build up in a wire... masure the resistance at start +1
Ft
of wire and you get X (very small resistance) as you move down the wire
the
resistance builds up because you keep adding resistance... get it now?
I
didnt explain that well enough the first time sorry...

Yes, it was unclear. Thanks for clarifying.


. Stripping half of the unneeded copper away won't be detrimental.

It sure as heck doesnt help,.,..,

Doesn't hurt either.

if i had 4 guage wire then removed the
copper so that i get a piece of 18 guage coming out of a 4 guage wire...
the 18 guage piece will get hot and go up in resistance... the 18 guage
piece cannot carry the current that is needed to support the amp...

If you're removing so much that it essentially becomes a fuse, then no it's
not good. But keep in mind how thick the traces are inside the amp.

people
who run 4 guage wire then cut away the coper to make like 10 guage would
have been better off just running 10 guage... they might get a little
bit more current carraying capibility with the 4 guage to 10 guage..

No, this doesn't make sense. Bottom line is this: resistance = resistivity
times length divided by cross-sectional area. Since the length of the
stripped piece is so short, it doesn't make any difference how thin it is to
the resistance of the wire (that is, until it gets so small that it becomes
a fuse - this is difficult to do). So running 8ga. and terminating it into
14ga. will still yield a higher resistance wire. Higher resistance than
running 10ga all the way back.

but not
for the price difference.... Remember electrons flow on the outside of a
copper conductor, stranded wire is better then solid wire...

This isn't exactly true. Electrons make use of the full diameter of the
wire. What you're referring to is the static assessment - that is,
electrons under steady-state conditions will reside on the outside of the
conductor.

Sorry i didnt explain the reson I said the battery was like a cap is
because
the voltagev on a battery cannot change insontainesoley... just like a
cap.

Not sure what you're getting at here. The voltage at the terminals of both
a battery and a capacitor can change instantaneously, depending on the
current draw. I think what you're referring to is that both batteries and
capacitors tend to act as low-pass filters when they're in parallel with the
alternator/amplifier circuit. While this is true, they do so by entirely
different mechanisms and therefore have entirely different modes of
operation.

You can put another battery right next to the amp i suppose.. then you
dont
have to worry about the size of the wire going to the amp and battery from
the alternator.. though the battery will lose its charge quickly if
playing
loudly... the alternator has to charge two batteries then...

Putting a 12v battery next to the amp will actually decrease the supply
voltage to the amp rather than increase it. This is because whenever the
system voltage is greater than 12v (which tends to be the bulk of the time),
the battery is actually drawing current rather than supplying it.

Ken An EE But college apparently means nothing but a piece of paper.

College can be useful, but it doesn't touch experience.

So running 8ga. and terminating it into
14ga. will still yield a higher resistance wire. Higher resistance than
running 10ga all the way back.

Oops. This should read lower resistance, not higher resistance.

"MZ" wrote in message
...
Ok thanks for the post.. i understand why people think caps are
bs... i get it now... im not fimilar with the interior working of an
amp..
for example i sure as heck didnt think they used +/- 90V to produce a
sound... i am still sceptical on this point ... however...

I think Eddie said 90v, which would imply +/-45v which is typical for
larger
amps.

Resistance doesn't "build up"

Resistance does build up in a wire... masure the resistance at start +1
Ft
of wire and you get X (very small resistance) as you move down the wire
the
resistance builds up because you keep adding resistance... get it now?
I
didnt explain that well enough the first time sorry...

Yes, it was unclear. Thanks for clarifying.

you got it



. Stripping half of the unneeded copper away won't be detrimental.

It sure as heck doesnt help,.,..,

Doesn't hurt either.

if i had 4 guage wire then removed the
copper so that i get a piece of 18 guage coming out of a 4 guage wire...
the 18 guage piece will get hot and go up in resistance... the 18 guage
piece cannot carry the current that is needed to support the amp...

If you're removing so much that it essentially becomes a fuse, then no
it's
not good. But keep in mind how thick the traces are inside the amp.
good point... there prolly not that large, although for the power i would
think a good amp uses copper planes rather then traces


people
who run 4 guage wire then cut away the coper to make like 10 guage would
have been better off just running 10 guage... they might get a
little
bit more current carraying capibility with the 4 guage to 10 guage..

No, this doesn't make sense. Bottom line is this: resistance =
resistivity
times length divided by cross-sectional area. Since the length of the
stripped piece is so short, it doesn't make any difference how thin it is
to
the resistance of the wire (that is, until it gets so small that it
becomes
a fuse - this is difficult to do). So running 8ga. and terminating it
into
14ga. will still yield a higher resistance wire. Higher resistance than
running 10ga all the way back.

but not
for the price difference.... Remember electrons flow on the outside of
a
copper conductor, stranded wire is better then solid wire...

This isn't exactly true. Electrons make use of the full diameter of the
wire. What you're referring to is the static assessment - that is,
electrons under steady-state conditions will reside on the outside of the
conductor.
And we dont have steady state conditions? its DC, and on average i think
the unit draws the same amount of current .. if so then yes the electronics
flow on the outside.. i would think... i dunno.. i better go check this
out


Sorry i didnt explain the reson I said the battery was like a cap is
because
the voltagev on a battery cannot change insontainesoley... just like a
cap.


Not sure what you're getting at here. The voltage at the terminals of
both
a battery and a capacitor can change instantaneously, depending on the
current draw. I think what you're referring to is that both batteries and
capacitors tend to act as low-pass filters when they're in parallel with
the
alternator/amplifier circuit. While this is true, they do so by entirely
different mechanisms and therefore have entirely different modes of
operation.

The voltage on a battery or a cap cannot (CANNOT) Change all at once.. it
is the properity of a cap.. you would need infinity currrent to do it...
good luck.


You can put another battery right next to the amp i suppose.. then you
dont
have to worry about the size of the wire going to the amp and battery
from
the alternator.. though the battery will lose its charge quickly if
playing
loudly... the alternator has to charge two batteries then...

Agreed with that

Putting a 12v battery next to the amp will actually decrease the supply
voltage to the amp rather than increase it. This is because whenever the
system voltage is greater than 12v (which tends to be the bulk of the
time),
the battery is actually drawing current rather than supplying it.

Agreed
Ken An EE But college apparently means nothing but a piece of paper.

College can be useful, but it doesn't touch experience.
quite right... im good with control systems

This isn't exactly true. Electrons make use of the full diameter of the
wire. What you're referring to is the static assessment - that is,
electrons under steady-state conditions will reside on the outside of
the
conductor.
And we dont have steady state conditions? its DC, and on average i
think
the unit draws the same amount of current .. if so then yes the
electronics
flow on the outside.. i would think... i dunno.. i better go check this
out

Ah, "steady state" would be the wrong term for it. Anyway, it's static vs.
dynamic. The electrons make use of the entire conductor. The evidence for
this is that resistance is defined in part by the cross-sectional area of
the conductor. Further evidence can be found by doing a search for the
"skin effect". The skin effect isn't exactly relevant to the question, but
it serves to illustrate a point. If you look at the boundary conditions by
setting the frequency to zero (DC), then you find that the calculated skin
depth (which, put simply, is the depth at which the conductor maintains a
certain level of resistance) specifies that the electrons use the entire
conducting volume. I can get a pdf'd page out to you, or anyone else,
interested in the skin effect if you'd like.

Not sure what you're getting at here. The voltage at the terminals of
both
a battery and a capacitor can change instantaneously, depending on the
current draw. I think what you're referring to is that both batteries
and
capacitors tend to act as low-pass filters when they're in parallel with
the
alternator/amplifier circuit. While this is true, they do so by
entirely
different mechanisms and therefore have entirely different modes of
operation.

The voltage on a battery or a cap cannot (CANNOT) Change all at once.. it
is the properity of a cap.. you would need infinity currrent to do it...
good luck.

v = v0 * e^(-t/RC)

That's the voltage of a discharging cap. I'm sure you're familiar with that
equation.

Take the derivative with respect to t (time) to identify how fast the
voltage can change.

dv/dt = v0 * (-t/RC) * e^(-t/RC)

It can certainly change. The parameters that affect the rate of change are
the initial voltage (v0), the current draw (indirectly specified by R), and
the capacitance. This change can be substantial, even for large capacitors.
Plug the numbers in yourself.

As for batteries, the voltage change is basically dictated by a voltage
divider rule.

v = v0 * Ra /(R0 + Ra)

where R0 is the output impedance of the battery and Ra indirectly specifies
the current draw of the amplifier. As you can see, the voltage drop with
the battery follows a very different time course.

College can be useful, but it doesn't touch experience.
quite right... im good with control systems

Ah, you're one of THEM.

Mercury wrote:


It sure as heck doesnt help,.,.., if i had 4 guage wire then removed the
copper so that i get a piece of 18 guage coming out of a 4 guage wire...

it sure can if it is short!
remember its not only the wire diameter, its the length as well.

the 18 guage piece will get hot and go up in resistance...

and I doubt anyone would wittle down a 4ga piece to 18ga.
if you have to take some strands off the outside to cram the
wire in a connector you usually just take off a little....

the 18 guage
piece cannot carry the current that is needed to support the amp... people
who run 4 guage wire then cut away the coper to make like 10 guage would
have been better off just running 10 guage...

not true, no matter how you whittle it down, you will have 15 ft of 4 ga
as opposed to 15 ft of 10ga which has more resistance.

Remember electrons flow on the outside of a
copper conductor, stranded wire is better then solid wire...

you have been reading to many wire brochures from stereo shoppes..

Skin effect does not occur to any degree to worry about untill you
get to VHF frequencies, were dealing WITH DC!!!!!
Skin effect NOTTA!!

Eddie Runner

"MZ" wrote in message
...
This isn't exactly true. Electrons make use of the full diameter of
the
wire. What you're referring to is the static assessment - that is,
electrons under steady-state conditions will reside on the outside of
the
conductor.
And we dont have steady state conditions? its DC, and on average i
think
the unit draws the same amount of current .. if so then yes the
electronics
flow on the outside.. i would think... i dunno.. i better go check
this
out

Ah, "steady state" would be the wrong term for it. Anyway, it's static
vs.
dynamic. The electrons make use of the entire conductor. The evidence
for
this is that resistance is defined in part by the cross-sectional area of
the conductor. Further evidence can be found by doing a search for the
"skin effect". The skin effect isn't exactly relevant to the question,
but
it serves to illustrate a point. If you look at the boundary conditions
by
setting the frequency to zero (DC), then you find that the calculated skin
depth (which, put simply, is the depth at which the conductor maintains a
certain level of resistance) specifies that the electrons use the entire
conducting volume. I can get a pdf'd page out to you, or anyone else,
interested in the skin effect if you'd like.

Put the link up or mail it to me im due for some good reading


Not sure what you're getting at here. The voltage at the terminals of
both
a battery and a capacitor can change instantaneously, depending on the
current draw. I think what you're referring to is that both batteries
and
capacitors tend to act as low-pass filters when they're in parallel
with
the
alternator/amplifier circuit. While this is true, they do so by
entirely
different mechanisms and therefore have entirely different modes of
operation.

The voltage on a battery or a cap cannot (CANNOT) Change all at once..
it
is the properity of a cap.. you would need infinity currrent to do
it...
good luck.

v = v0 * e^(-t/RC)

That's the voltage of a discharging cap. I'm sure you're familiar with
that
equation.

Take the derivative with respect to t (time) to identify how fast the
voltage can change.

dv/dt = v0 * (-t/RC) * e^(-t/RC)

It can certainly change. The parameters that affect the rate of change
are
the initial voltage (v0), the current draw (indirectly specified by R),
and
the capacitance. This change can be substantial, even for large
capacitors.
Plug the numbers in yourself.

Yeah voltage can surely change on a cap... to have it change in 0 time...
well forget it.. for excample you can put 12V across a resistor in 0 time
(given that there are no capacitive components on the resistor)

there is a charging time.. 5 tou... that onmly gets you to 93 or 96% i
cant remember the number exactly... but anyway there are 5 time constants
that you need to get to "full" charge... never instant....


As for batteries, the voltage change is basically dictated by a voltage
divider rule.

v = v0 * Ra /(R0 + Ra)

where R0 is the output impedance of the battery and Ra indirectly
specifies
the current draw of the amplifier. As you can see, the voltage drop with
the battery follows a very different time course.


College can be useful, but it doesn't touch experience.
quite right... im good with control systems

Ah, you're one of THEM.

I am.. if you have questions on digital design or microcontroller
programming i can help.. otherwise im just full of foggy information from
school

Mercury wrote:

Understood... I am sure the car has some crap on the 12V rail that can be
considered noisy to the amplifier as well.

True, but typicly any power wire ripple cant get into the amp because
the amp changes EVERYTHING comong in to AC and then back to
DC before it is stored in the power supply rails (caps)... So anything
coming in is chopped up and straightened back out.... (the choppin up
is far more severe than any noise coming in!)


First of all a 1F cap is expensive enough at 20 volts... buy one at 90
Volts (it would be huge first of all and prolly cost a grand)

true, specially if it is all gold and fancy (Jewelry) looking....
They also dont want folks opening the amps to try this modification...

You can get some surplus caps of several 100,000 Mfds that are high
enough voltage from $10 and up... We used to do this a bunch back in
the late 70s and early 80s....

I dare you to push 50 amps (just picking numbers now) through a 4 guage
wire that was reduced to the diamater of a 20 guage wire for 1 inch) guess
what... that small diamater will act like a fuse I assume the same thing
in a car... explain it to me if i am wrong please...

You CAN make a fuse that way if youwish.. ;-)


So the amp doesnt mind large voltage swings?

depends on how large the voltage swings are...

Caps have a better purpose in the other world of electtronics.. maybe not as
large cans as proven to me but in digital world they are used all over
the small ceramic ones...

Caps are caps... They dont really hurt anything if you can afford them.
its just debateable how much good they will do you in the average car audio
system.... I wouldnt use caps unless I have many many amps, and then I
wouldnt probably need them, I would only put em in there so folks will
think they look cool... (hey im in the audio biz, if I use caps maybe folks
will buy em from my store!!)


Eddie Runner

Put the link up or mail it to me im due for some good reading

Will do. I assume the email address that you're listed under here is valid?

Yeah voltage can surely change on a cap... to have it change in 0 time...
well forget it.. for excample you can put 12V across a resistor in 0
time
(given that there are no capacitive components on the resistor)

Right, but in the real world, there's no such thing as instantaneous (0
time). Even superconductors can't attain that. Audio systems are rather
simple, since switching power supplies usually won't extend beyond 100kHz.
And, much more importantly, musical transients are on the order of hundreds
of Hz. Leave "instantaneous" in the computer realm.


there is a charging time.. 5 tou... that onmly gets you to 93 or 96%
i
cant remember the number exactly... but anyway there are 5 time
constants
that you need to get to "full" charge... never instant....

5 tau is an arbitrary number. Especially for our purposes, where the cap
voltage never dips below about 12v to begin with.

The bottom line is that neither the cap nor the battery can deliver current
instantaneously. But they can be modeled as such in the system we're
describing. In fact, the "least instantaneous" device is probably the
alternator, because it has a delayed feedback mechanism to contend with.

Understood... please see my post 2003 F250 component speaker system.. i
would like to hear your useful feedback on that topic...

I have an 03 f250 and i want it to sound really good.. im new at all this
and am willing to spend dsay 7 - 800 bux

Kenny
"MZ" wrote in message
...
Put the link up or mail it to me im due for some good reading

Will do. I assume the email address that you're listed under here is
valid?

Yeah voltage can surely change on a cap... to have it change in 0
time...
well forget it.. for excample you can put 12V across a resistor in 0
time
(given that there are no capacitive components on the resistor)

Right, but in the real world, there's no such thing as instantaneous (0
time). Even superconductors can't attain that. Audio systems are rather
simple, since switching power supplies usually won't extend beyond 100kHz.
And, much more importantly, musical transients are on the order of
hundreds
of Hz. Leave "instantaneous" in the computer realm.


there is a charging time.. 5 tou... that onmly gets you to 93 or 96%
i
cant remember the number exactly... but anyway there are 5 time
constants
that you need to get to "full" charge... never instant....

5 tau is an arbitrary number. Especially for our purposes, where the cap
voltage never dips below about 12v to begin with.

The bottom line is that neither the cap nor the battery can deliver
current
instantaneously. But they can be modeled as such in the system we're
describing. In fact, the "least instantaneous" device is probably the
alternator, because it has a delayed feedback mechanism to contend with.

I have heard a couple installations where Pyramid equipment actually
sounded GOOD. For the amount of gear that it was, it definately
wasn't AWESOME, but it was good, and for the $$$ invested in the
systems, they were pretty good bang for the buck.

That was with some amps that were 4 x 250 watts, Pyramid Pro Plus 12"
woofers (with the woven kevlar cones..). I am pretty sure that their
speakers are made by various suppliers (those Pro Plus's looked an
awful lot like the Eminence 12"s that I had at the time).

I remember back in the day that I had a Pyramid EQ/Booster that I
bought for my first system. I remember the quote from the instruction
sheet was "This automotive amplifier will produce 240 watts/channel
(I.L.S.) into a load of 4 ohms". A few weeks after I bought it, I
decided to upgrade my rear speakers, and got talked into an Alpine 30
watt/channel amp for the rear speakers. They told me if that amp
didn't put out more power than the EQ, they would gladly take it back.
Needless to say, it was so much louder and cleaner than the EQ/booster
that it wasn't funny.

Anyways, I ended up blowing up that little EQ/booster and brought it
back to the store I bought it from to see if there was any type of
warranty on it, and of course there wasn't. The salesman that I
bought it from was a good friend of mine, so there was no hard
feelings. I just wanted to know what that "ILS" power was. He talked
with their repair tech, and he didn't know, so he called the engineers
at Pyramid. Their response was "IF LIGHTNING STRIKES". They said
that current car standards allow them to pump as much voltage through
the amp as they want, then measure current draw, and there is also no
regulations on how long it has to be able to put out that amount of
power (I am guessing microseconds or smaller). Multiply them
together, and you get ILS watts.

"Steve Grauman" wrote in message
...
Im not sure Pyramid lies about thier power ratings anymore than
many other car stereo manufacturers... Lots of them lie!!

Most of them "lie" if that's the word you want to use. Sadly, there seems
to be
so many variables in how each company rates RMS and Peak power outputs
that variances will occur, even when the manufacturer is attempting to be
honest. I happen to know that JL's 300/4 (rated at 85x4 if memory serves me)
actually
makes somewhere in the neighborhood of 100 watts per channel. And PG's
Titanium series amps are always underrated.

until there is an industry wide standard there is no real use in debating
peak power. I think you should by what you need and let the EE's debate the
rest.

"Lawrence K. Evert Jr." wrote in message
...
In my experiance JL has always underrated their amps, thus the nickname
"cheater amp" comes to mind if any of you have heard of older JL amps
referred to as such. I have an old 360a that kicks the crap out of 2
JL12W08's hooked up to it, (and if you couldn't tell) they are 8 ohm
speakers.

JL, didn't make amps when "cheater amps" were all the rage. Orion had the
best example. but under-rating really means nothing look at PPI they're
about spot on.