RE: [Chevelle-List] Stereo question.

[Chevelle 69]

Title: Message

The Capacitor does store energy in the form of voltage potential on the plate. It's the effect of the voltage felt on one plate inside that causes the other plate to eventually feel the potential. The way a capacitor filters is by passing the potential felt on one plate through to the other plate without actually flowing direct current. So the energy felt on one side is kind of magnetically bled off to the other plate which is going to be electrically at ground. This means that any spikes in voltage at the one plate will be stored in the plate on the positive side, then bled off magnetically to the plate that goes to ground. AC passes through a capacitor in this way and since there is no direct connection between the plates, DC (Direct current) can't pass through ..or else you'd have a short to ground. So the AC spikes are passed to ground through the circuit the capacitor provides for them.   This filter capacitor is going to be placed at the power supply side of the electronics where it can filter the DC for any spikes before it gets into the electronics, which could effect many things. It should have no effect on internal electronics by itself.   And, if the power were taken only from the battery then there would be no need for filters. A battery provides extremely clean DC itself, so if the sound system were to be turned on while the engine was not running it should be just fine assuming the problem is in the power being supplied and not the relays chattering.   It might be a great test to try this Herb! Run the stereo while the car is off until the fans kick in. It should tell you if it's the power not being clean enough ....or if it's the relays chattering.   However, I can assure you the battery would quickly go dead if the lights and stereo and other things were turned on while the car engine was not running. The alternator provides the power to keep electrical components supplied when the car is running. When the regulator senses that the alternator needs to start putting out more due to an increase in demand, the regulator can possibly cause a spike and the alternator sends a power surge down the line to keep up with demand. This power surge may be more than the sensitive electronics can handle without passing it on to other circuits. Especially since you are amplifying things tremendously with that amp.   By the way, it gets rather involved, but if you get too large of a value of capacitor, which is rated in value in microfarads in most electronics, then the spike may not have time to bleed off if it's a fast spike. It will pass whatever the capacitor doesn't have time to pass on to the electronics. You want a fairly fast reaction between the plates to handle fast spikes, this means a lower value would be best for extremely fast spikes. But since you don't know how fast your spike is coming without having equipment to measure it when it happens, it's best to try a moderate value to see if it helps at all. Bigger is not always better in everything.   If you were to create that Pi filter you might try a smaller value cap on power supply side of the choke coil to pass the fast spikes to ground and a larger size cap on the electronics side to finish filtering the DC to a smoother level.   Capacitors are also rated in their ability to handle voltage. While 12 volts is not enough to be any trouble for most capacitors, the spike could possibly be up to several hundred volts for a very short time period.   While the capacitor is a voltage device, a choke is a current device. Electronically it is just a piece of wire made into a coil, but the characteristics of how many turns, the diameter of the wire etc. gets pretty hairy when figuring out the value in Henry's. So a choke passes DC current through it just fine ..no problem ....but when an AC component floats on the DC line, or a sudden surge in DC happens, the magnetic properties that a coil has opposes a sudden change in current.     That's why a Pi filter is so good, it gives any spikes or AC riding on a DC circuit a "triple whammy". Considering that your alternator is an AC power supply, and has to be rectified and filtered, and it may not be enough at times to handle huge surges in demand. your sensitive electronics just may need a little extra help in filtering out stuff that wasn't intended for it to handle.   I have to suspect that the engineers have the recommended sizes given to the stereo stores to handle problems like this and I'd go with what they recommend. Not sure I'd trust the decisions to the guy that installs the stereo though unless he's very experienced and has electronics training in college.                                                                                                               Steve      -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Rodney. Sent: Sunday, October 06, 2002 2:53 AM To: [EMAIL PROTECTED] Subject: Re: [Chevelle-List] Stereo question. Hey Herb,   I don't think a cap will prohibit this "thump" sound from happening.  My understanding of a cap is that it "stores" power so that when you hit a deep bass note, it'll hit with full force or power.  You're obviously getting enough power to make this "thump" sound so you shouldn't need more power from a reserve storage of power.  If anything that'll make the "thump" sound stronger.    The cap is usually for a problem like your when your headlights dim at night when deep bass notes are played.  The normal power from the battery runs the headlights (and everything else) at a consistent power level and then the deep bass note uses the normal power plus whatever reserve power is stored in the cap.   To stop this "thump" you have I think you're looking for something like this  http://www.sounddomain.com/sku/STISPSON     Rodney. 71 Chevelle El Mirage, AZ       ----- Original Message ----- From: Herbert Lumpp To: Chevelle List Sent: Saturday, October 05, 2002 5:09 PM Subject: [Chevelle-List] Stereo question. Ok all you stereo gurus...  Hopefully somebody can help, the guys at the local stereo store are stumped.   If I have my stereo on (not loud but normal listening volume) and the electric fans kick on, I get a huge thump through the woofers.   The alternator is a CS130 putting out 105 amps.  The fans turn on/off with a thermo switch through a pair of relays.  The sub amp is running 6 gauge power wire directly off the battery and the fans' main power feed off the alternator.   It sounds to me like the fans are causing the alternator to suddenly put out some juice and the sudden power output is causing a surge through the system resulting in a huge thump through the woofers.  Am I on the right track or way off base? (no pun intended)  Will one of those big capacitors in the power line to the amp absorb the surge or do I need to try something else?   Thanks. cYa-   Herb Lumpp 1966 El Camino ACES 3509, MCC 528 http://users.adelphia.net/~hlump/