Audio Capacitors - Stiffening Capacitors 101

On one end of the amplifier are heavy-duty, gold-plated, brass terminals. The terminals accept #0 gauge power wire for charging and have an additional four #4 gauge for each of the power and ground output terminals. A third terminal is for remote turn-on. The remote turn-on powers the three triangulated blue LEDs on the top of the unit.

Inside, the PowerCore 20-farad capacitor is constructed with 288 four-farad, 2.5-volt capacitors wired in eight series strings of 36 parallel caps. We measured 16.3 farads using our constant current charging method.

This unit appears to still be in the prototype stage. Once the company gets it ready for production, we think the leakage current will be minimal or zero.

From the Discharge Time graph above, we measured 0.008 ohm ESR. Again, a very respectable value. Also, note that our method above can result in five to 10 percent measurement error.

We could not find this cap on Phoenix Gold's web site (www.phoenixgold.com) but it should be up by the time you red this.

Lightning Audio Strike LSD10DT XStatic Supercap 100 Alumapro C.A.P. 50

Lightning Audio Strike LSD10DTIt wouldn't be a capacitor test without Lightning Audio. The company started back in 1992 and was the first major player in the capacitor game. For years following, it was the largest supplier of capacitors to the industry. To not include one of the leaders in the technology would be considered a sin.

The Strike LSD10DT is your typical cylindrical capacitor. We chose this particular unit because it is an offspring of the original design. This unit is rated at 1 farad and includes a voltage readout LED display. Although the Strike may be an ordinary electrolytic design, it does have a very low ESR.

We verified that this cap is indeed a 1-farad capacitor. As the ESR was very low, it was difficult to measure with our test setup. We got 0.005 ohms, but this measurement could be off as well because the value is so low.

Our only gripe with the Strike capacitor was with the voltmeter and associated electronics. While at idle, the capacitor had a current leakage of 70mA that could kill a battery if the vehicle was not used for extended periods of time.

Check out this and the rest of Lightning's lineup at www.lightningaudio.com.

Whatever you want to call them, EDLC, stiffening, supercap, or ultracap, it appears that they aren't of much help for the SPLer, except to stabilize the system voltage for the head unit and signal processors. However, for clean audio and improved transient power, these capacitors can extend the battery and improve the audio performance, including reducing harmonic distortion in the low frequencies.

ESR and Current Capacity A perfect capacitor has no resistance. If you shorted a perfect cap, it would deliver an infinite amount of current for an infinitely short period of time. The ESR limits the current during this time to what Ohm's law predicts: I = E/R (I = Current, E = Voltage, R = Resistance). In simplified terms, ESR relates to the total instant power the capacitor is capable of producing.

For example, if a cap is charged to 14 volts with an ESR of 0.01 ohms of ESR, the instantaneous current is 14/0.01 = 1400 amps. But we are not shorting the cap - the amount of current it could deliver depends on two voltages, the voltage before the transient, and the battery voltage under heavy load, as well as other parameters such as the rise time of the transient. An ESR of zero is best and 0.01 is good.

Relating a Farad to a CapacitorCapacitance, or the number of farads, relates to time and total energy stored. For example, the instantaneous current or power is determined by the ESR. How long the cap can deliver power (or total energy) is determined by its capacitance.

Power is measured in watts and does not factor in time. For example, a 100-watt light bulb is consuming 100 watts at any point in time. This is called power. A 100-watt bulb that is on for one hour has consumed 100 watt-hours of energy.

A farad could be compared to a battery's Ampere-hour measurement. This specifies the capacitor's ability to store energy.