EvgeshaIS300

which capacitor to get?

250/1 amp and 10" JL sub

dimming dash lights never bothered me until now.
will getting capacitor fix my problem?

how do i determine how many farads do i need. i'm not planning to upgrade my system so no need to account for more amps. and will i need to modifi my curent electrical line. or does it just plugs in in-line between my amp and baterry?

i'm on the budget so Xstatic Supercap is out of question

engin_ear

iTrader: (1)

You can get a 1/2 Farad to 1 Farad cap. Lightning Audio, Rockford Fosgate, and others are OK. Just make sure you get a low ESR (equivalent series resistance) cap, or you'll be wasting your money because it won't work very well. Also, when you wire it up, make sure the wires from the cap to the amp are heavy and short to minimize the path resistance.

DPGS430

I'm running 2 500/1's and a 300/4 and "was" using an Alumapro 5 farad cap. I was told and now believe that because they are class D amps the cap will only hurt the current they need. I removed the cap and noticed quite a bit more clarity and bass response. I'm running 2ga for power and ground with a Optima Yellow top battery. I have no issues at all with dimming lights.

Jim

engin_ear

iTrader: (1)

Jim:

What's up with that? I'd love to hear THIS story, something seems wrong, it's not making intuitive engineering sense, but maybe there's something to it. Please post here or PM me if you get a chance.
Jerry

johnee78

iTrader: (4)

The fact that it's a class d amp doesn't have anything to do with the cap.JL audio amps are regulated meaning if you give them more power they will not give more because they are already working at full potential even at 10.5 volts.Also the 300/4 is an AB amp not class D. You may want to check your system..

johnee78

iTrader: (4)

You may want to upgrade your ground off of your battery.For example, if the factory ground is 8 gauge, you may want to upgrade to a 4gauge and upgrade to a better battery if you haven't already...Also a 1 farad or 1/2 farad would be fine.Your running a very efficient amp, good choice..

DPGS430

An installer locally told me this, he does a lot of high-end installs with JL monoblock amps. Yes they are regulated like Johnee78 says and that's probably what the installer was referring to. I did not hear the full potential of my system until I removed the cap. The cap was brand new, but then a cap will only do so much. And yes, the 300/4 may be an AB amp but the monoblock are definately D's.

Jim

engin_ear

iTrader: (1)

The only difference between a Class-D amp and an A or AB is that the output signal a Class-D generates is pulse-width-modulated, and its high frequency modulation is filtered out either by a filter in the output stage prior to the woofer, and/or the woofer coil itself, generating the same basic waveform that a Class-A or AB generates (the baseband audio signal). The output driver stage of a Class-D is inherently efficient, and consumes very little power within itself, unlike a Class-A or AB (especially a Class-A). However, for a given input signal and amplifier gain, a Class-D amp has exactly the same dynamic current/power requirements as a Class-A or AB, and actually has less of a static current requirement, which is mainly why it runs cooler. (It has to be - both the sound and power coming out of the woofer is the same in both cases). The switching modulation of the Class-D does not matter to the amp's power requirements in anything other than the average sense, i.e. in the DC to 20KHz band. I also don't see what the power regulation that the 500/1 does has to do with it, vs. having a cap or not.
I suspect that there is something else at play here (other than the class of the amp vs. the cap) if your experience of additional clarity without the cap is real. Having said that, I'm running the same amps that you are, a 500/1 and a 300/4 (they're great !). This makes me want to disconnect my cap to see if I get any real difference, but it's too much of a pain in the a$$. Then again, psychoacoustics has a nasty way of playing tricks on the mind...By that I mean that the perception of a change in sound has been experienced by many people when there actually is none. I've been part of many tests over the years where nothing in a test setup was changed at all, including the source material, and people have reported a perceived difference. If you're actually finding a difference in your system, there just may be something about the cap/wiring/amps that you have that is causing it. However, if anyone has any additional technical information as to why this might occur, I'd love to hear it....

For Class-D amplifier tech info, here's a link to a paper from the Georgia Tech EE Dept, written by W. Marshall Leach, an AES Review Board member:
users.ece.gatech.edu/~mleach/ece4435/f01/ClassD2.pdf

Note that, if the Class-D amp required anything other than the power that was going to the woofer, it would be dissipated as heat in the amp itself. We know that this is not the case.

Jerry.

johnee78

iTrader: (4)

A 50 Farad cap Do you have any idea what kind of upgrades you would have to do to the electrical system of vehicle to handle the load of a cap that size??? Remember, for those who are not aware of how a cap works.It has to "fill up" with power and the strain for a stock electrical system to do that would be tremendous.It would actually be doing more bad than good.Stick with a 1/2 to 1 farad cap and you'll be fine, you can try monster, lighting audio, scosche, etc..Ebay is a good place to check ..Don't forget to upgrade your ground!!!!