How to Tell if Power Cap is Bad

maka78 · Post by **maka78** » Thu Sep 18, 2008 6:42 am

Back to topic... is it necessary to use a huge cap to power a system? For instance, I've heard 1000w RMS = 1 Farad cap is a good rule of thumb. Should I follow this, or is this false?

How many farads is sufficient for a sound system with around 3500w RMS?

Post by **stipud** » Thu Sep 18, 2008 6:59 am

oyvind wrote:Since this topic started as a capacitor discussion, here is another question.

1 large capacitor or several small in paralelle?

I want to add som capacitors to my system. In the old days (1998) the discussion was if a 1 farad capacitor could release the power fast enough to make a difference. Has there been an conclusion to that discussion? Will two 0.5 farad capacitors in paralelle be any faster? They are a bit more expensive than the 1 farads. I have done my homework and

By the way, whats up with the price difference between all the different brands of 1 farad capacitors? Isn't a capacitor a capacitor?

That depends on the ESR (electric series resistance) of the capacitors.

Generally, smaller caps have lower ESR. Also, running caps in parallel reduces ESR further, since it distributes the load. So usually many small caps perform much better than single large ones. Not all capacitors are created equally though, so i'm sure there are some large caps with lower ESR than certain brands of smaller ones.

PG's first PowerGrid and PowerCore 10 and 20 farad capacitors used an array of very many small capacitors to provide the power. This offered the most capacitance with the lowest ESR. Unfortunately, more caps means more things that can break. Capacitors start leaking after awhile, and need to be replaced, before they short out and cause damage to the circuit board. With that many caps, it could even be a fire hazard.

So PG discontinued them, and replaced it with the PowerCore 15 farad capacitor, which housed a single carbon aerogel type capacitor from Alumapro. This had a much lower ESR but is way safer.

KHPower · Post by **KHPower** » Thu Sep 18, 2008 11:37 am

maka78 wrote:
KHPower wrote:Great topic! I use a 5 farad cap bank to keep everything clean and it also works great for a distribution block.

i was feeding 7.88 volts to the ZX500 and noticed my headlights and interior lights dimming up like crazy and I guess the 7.88volts going to it was making it clip. It doest sound like clipping but I guess it is.

I thought that Phoenix Gold's tech said all there amps can handle a 8 volt load????????
'

When you say 7.88V, you mean input volts from the HU to the amp?

Yep , well actually 5 volts from the deck into the PG sld 44 and over 8 volts from the SLD44 to the basscube , then 7.88 volts from the basscube to the amp.

I cant get any more voltage throug my basscube other than 7.88 volts

deathcloud · Post by **deathcloud** » Thu Sep 18, 2008 12:56 pm

So I just bought a powercore 15 farad capacitor and im glad your saying that this is a better one than the others.

Its going in my dads truck. I love how it is a distro block as well. Thats totally cool.

Picked one up for 240 shipped. I think that was a pretty good deal.

I could be andy and sell it for 500 bucks shipped. any takers?

JKJKJK haha

But yea that should be solid in his setup. Pretty excited.

oyvind · Post by **oyvind** » Thu Sep 25, 2008 5:16 pm

Is less than 0.001Ohms considered a low ESR in a 1 farad cap? And is it nessesary with a separate ground wire for the power cap?

Post by **mhyde71** » Wed Oct 01, 2008 7:47 pm

hey thanks tom... just got my fuse and battery replaced in my dmm... and look forward to gettin'er done!

thanks a-bunch

Post by **mhyde71** » Sun Oct 05, 2008 12:03 pm

@ TOM...

I did as you instructed/pointed out to set the gains..
here's what took place...:
1st) at first I didnt have sine waves on CD, so I ran them on my MP3 player.... whoa.. gee whiz.. the numbers were high...! The gains had to be all way down to be in ball park of the numbers indicated above...

2nd) I burned the sine's onto a CD and they were like just the opposite... The gains had to be at/around 80% before reaching the desired numbers...

So what do I do.. given that I mostly use the MP3, should I go with that as my media of choice for setting gains??? and if so.. I almost never listen to "music" i mostly watch videos... and wonder if I should try to get a sine wave on/as video.. but isnt it true that MP3 is embedded in videos to give the audio track?? so just do the MP3 sine and set with that??

I dunno... what do you think...

Post by **stipud** » Sun Oct 05, 2008 2:07 pm

That's pretty weird man. You are supposed to burn them as a CD, not MP3 files. Do mp3s sound noticably louder?

Post by **mhyde71** » Sun Oct 05, 2008 3:17 pm

stipud wrote:That's pretty weird man. You are supposed to burn them as a CD, not MP3 files. Do mp3s sound noticably louder?

well yeah I burned them as an audio cd.. but when/if I play them off the MP3 play (ipod), I'm assuming they are MP3 File Format.. they are much louder... and given that I almost always use Ipod (video Ipod, to play videos) maybe I should set gains under the MP3 Format protocol??

BUT AND A BIG BUT... that when I turn gains up to where they "are supposed to be" I hear more engine whine that when they are down.. meaning that appearantly my signal isn't clean clean.. but when they are set a lil lower poof I dont hear the engine whine any longer... Now this is even after grounding the RCA's, but before I did that (grounding RCA's) the engine whine was REALLY REALLY bad.. even with gains down...

SO with all that been said.. My gains are at about half of where they "should be" as if I gain set with an audio CD... Maybe something to do with the sine wave I have on hard disk and... after just now looking at the description of file format of the sine waves I have... I looked and they are MP3 File format.. should they be something different??? Can an MP3 be burnt as an Audio CD (AKA CD file format)??? I dunno and anyone can chime in.. if anyone else has some input..

Post by **stipud** » Sun Oct 05, 2008 4:03 pm

You don't have the iPod's EQ enabled do you?

Post by **mhyde71** » Sun Oct 05, 2008 5:17 pm

stipud wrote:You don't have the iPod's EQ enabled do you?

didnt knew it could when using it as TV Out, but will check on that... IOW dont believe so...

Post by **stipud** » Mon Oct 06, 2008 6:37 am

Make sure your HU doesn't have the input gain cranked either. It's pretty odd for the iPod source to be way louder. Usually the HU manufacturer will try to match the line-in to the -0dB CD reference level.

If you can't get it to match, then I suppose you would have to set gains through the iPod instead, if you listen to that more.

Post by **mhyde71** » Mon Oct 06, 2008 6:42 am

stipud wrote:Make sure your HU doesn't have the input gain cranked either. It's pretty odd for the iPod source to be way louder. Usually the HU manufacturer will try to match the line-in to the -0dB CD reference level.

If you can't get it to match, then I suppose you would have to set gains through the iPod instead, if you listen to that more.

yeah kinda what I figured.. there is a SLA feature... where you can adjust the Sound Level up/down on other sources, compared to the FM modulation on the Avic-Z1... but i had that at 0... i.e. no attenuation versus the FM receiver.

Post by **stipud** » Mon Oct 06, 2008 8:20 am

Try to match your sources as closely as possible... that way your gains will be matched across the board.

How to Tell if Power Cap is Bad

Re: Back to capacitors...

Low ESR