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Old 10th September 2011, 06:26 AM   #11
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The OP compares a car amp to a home amp, for capacitor size, which confuses things.
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Old 14th September 2011, 08:46 AM   #12
gens is offline gens  Croatia
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1'st car batery cant give over 100A without considrable voltage drop(thats without the wires), and thats 1.1kW while a car amp uses far less

2'nd ripple, pump noise and all dont matter if you have a good regulated power supply, as most are

3'rd Maxwell Technologies - Products - Ultracapacitor - 16 Volt Small Modules - General Purpose Modules
this is 350F/16V, its expencive and new, large one might be 1000F, but i doubt some1 woud use it for starting cars

all in all 1F at the input of the amp and 6mm2 wires is too much
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Old 14th September 2011, 04:08 PM   #13
Ron AKA is offline Ron AKA  Canada
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In car amps as was already posted you have a switching power supply which is a much higher frequency than the 120 Hz ripple you see off the bridge on a home system. As a result you need much less capacitance to smooth the ripple. Even in a home system the value of large capacitance in a class AB amp is quite small, to the point of being trivial. All you are doing is smoothing the ripple by a fraction of a volt, so you have a fraction of a volt more available before clipping. The article at the link below has more detail.

Increasing Transformer and Capacitor Size
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Old 14th September 2011, 04:13 PM   #14
tinitus is offline tinitus  Europe
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I moved you to CarAudio

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Old 16th September 2011, 07:47 AM   #15
djk is offline djk
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"but i doubt some1 woud use it for starting cars"

Batteryless, Environmentally Friendly Car/Truck

For several weeks Larry Schlussler at Sun Frost has been driving his 1982 Ford truck without a starting battery. The battery was removed and replaced by a large capacitor. The 150 farad capacitor is about 1000 times larger than the large capacitor commonly encountered in devices. The energy storage device is capable of storing enough energy to start a very large truck engine. What is needed to start an engine is actually not a large amount of energy but a short burst of power. A capacitor can supply an even larger burst of power than a starting battery. An additional advantage of a capacitor as a starting device is that its output is not affected as much as a starting battery’s during cold weather. The capacitor is about the same size as a starting battery.


The 1000F capacitor I mentioned was used for starting tractor-trailer rigs (semi).

provides up to 3000 amps of instant cranking power for any fleet
application, heavy equipment and military vehicles.

Delivers up to 3000 amps of cranking power at 12 volts

Capacitor Powered

30 second charge provides full cranking power

No lead/acid batteries to maintain or replace

Never needs to be plugged into AC power
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Last edited by djk; 16th September 2011 at 08:10 AM.
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Old 16th September 2011, 12:09 PM   #16
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Looks like supercaps may replace car batteries in the future.

You can never have too much 12v power. I have dual batteries and 1farad cap just to help with starting and for running 120v power ac inverters, don't even have audio amp in my car.
You can call me Mad Professor, building crazy experiments in my Electronics Workshop
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Old 16th September 2011, 12:44 PM   #17
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Originally Posted by muddasirwaheedmalik View Post
i have just seen some latest focal car amps and some other high end stuff which is meaner on power supply regulation capacirtos mostly after step up stage in the car amp its around 6500uf total for an amp rated 150 w per channelx2 now i was comparing it with vintage sony home amps with dual capacitor banks...12000UFx2 for the power module and 5500uFx2 for the amplificatier small signal......for sony TNA 330 ES vintage amplifer which is rated mere 110 W per channel. The focal 2.150 car amp is no cheaper both are class A/B but focal lacks dynamics even on reference series car components.....just a hint that the the capacitor bank in the vintage sony were lined up on the PCE then dual held together with plated coated with red velved for vibration control and then even individual cpacitor is stripped across is mid with an iron strip secured with a screw to eliminate vibtaion... the chasis is mad of pure aluminium must be 10 kg alone and the transformers are toriod in sheileded heavy cast metal....whereas the focal car amps have open step up transformers wotout shielding......>>>Sony ta-n330es image by McPics on Photobucket
Sony ta-n330es image by McPics on Photobucket
Sony ta-n330es image by McPics on Photobucket

just wanted to check would there be any benefit of addiing 12000uf capacitor bank X2 on both rails insteasd of 3300 dual bank...on my Focal 2.150.

Some reader may be misled I think , the author of this post as I understand compares his Sony home amp capacitor bank supply to his car audio amp capacitor bank supply. whilst both are capacitors the Sony is pushing and pulling partial DC from a bridge rectifier originating from a AC supply using capacitors to try to make DC.

The rule of thumb with AC derived power supplies so as not to break rectifiers is 1000 uf for every amp of current that the amplifier under load will deliver. for instance 10,000 uf per rail enables 5 amps of current each rail/ each channel.

If you try and put 1 farad of capacitance through a AC derived PSU either stand back whilst the rectifier evaporates, or properly design for that capacitance- just quietly thats a big bridge rectifier. Switch Mode PSU's cleverly change the frequency of AC so the need of big capacitors filling up and and being drawn from is nearly removed. There has been trend in recent times to use SMPS, and a few hours studying them is well worth while.They are complex, and bring together many ideas how DC can be derived.

Now where the two technologies car and home hi fi can have a romantic dinner together is to stop using ridiculous amounts of capacitance and instead use a transistor arranged as an emitter follower, and place capacitance from base to ground, like magic the transistors HFE characteristic will multiply the capacitance value. Not only that but bandwidth improves. See opamp - opamp construction as shown here a op amp psu greatly benefits from an emitter follower.

Hope this helps / Chris

Last edited by Chris Daly; 16th September 2011 at 12:56 PM.
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Old 16th September 2011, 09:06 PM   #18
djk is offline djk
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"for instance 10,000 uf per rail enables 5 amps of current each rail/ each channel. "

Crown made a 7KW/0.5Ω amplifier with only a single 10,000ĶF filter capacitor, it used a 60hz supply (non-swichmode).
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