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Old 4th December 2004, 01:11 AM   #1
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Default Question regarding capacitors

I posted this over at the avsforum but am not getting any replies. I did so because of the huge Crown XLS402 thread over there. Hopefully you guys can shed some light on this question.

The Crown XLS402 has (4) 4700 uF capacitors for a total rating of 18,800 uF. I just picked up a few of those Audiosource $25 plate amps that someone rated around 100w 8ohm, 125 4ohm. After opening it up I see it has (2) of the same capacitors the XLS402 has, dual 4700uF = 9400uF. Now, I just received two plate amps pulled out of Polk RT3000p towers that are rated at 300w RMS and they have DUAL 15,000 uF capacitors in them. Monsters! That's over 50% more rating then the XLS402! Now, does capacitor size have anything to do with how much power this thing can put out continuously or does it just help for quick HUGE power needs? The back of the Polk amp states 420w consumption while the Crown states 1000w.

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Old 4th December 2004, 01:52 AM   #2
Mr Evil is offline Mr Evil  United Kingdom
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Larger capacitors mean lower ripple, which means the minimum rail voltage will be higher, which means the maximum output power can be higher for a given nominal rail voltage.
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Old 4th December 2004, 02:45 AM   #3
Stocker is offline Stocker  United States
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And, if the increase is on the order of 2x or 3x or more, you can get a slight increase when the bass SLAMS.
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Old 5th December 2004, 12:04 AM   #4
djk is offline djk
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Considering a one FARAD cap can provide one amp for one second, how many amps did you say you needed?

Is 10,000F adequate for 25W? Most people would think so.

How about 100W? The energy stored will quadruple as the supply voltage doubles, so if 10,000F was adequate for 25W then it is adequate for 100W too.

Ditto 400W

Ditto 1600W

Ditto 6400W

The Crown MA10K does 7KW RMS, 10KW peak.

It uses a single 10,000F cap.

As do most of the Macrotech series (one cap per channel, they're all bridge amps).

I consider 90% regulation the point of diminishing return.

60hz, 3300F and an 8 onm load will do this.

A stereo amp for 4 ohms would need 3300+3300+3300+3300, or a pair of 13,200 for a common supply.

A Crown DC300A uses a pair of 13,500F

For 50hz increase to 4000F per each 8 ohm per channel.

An Ampzilla uses a pair of 16,800F

An SAE 2400 uses a pair of 16,800F

A Crest 6000 uses 120,000F, sound like a lot? It is rated at 2 ohms so it should have a pair of 16,000F per channel. It has dual mono supplies and two supply tiers, for a total of 8 supplies. It has 8 pcs 15,000F (120,000F total), or the point of diminishing return.

Caps store energy, a transformer sources it.

You want more slam buy more transformer.

An Altec 9440 has only two 9,800 caps total, is only rated at half the RMS power that the Crest 6000 has (with its 120,000F of caps), but it has more slam!

The transformer has twice the VA rating that the Crest does.

Regulating the 50mA or so that your front end needs will do more for the sound than the adding of 100,000F will.
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