improving amplifier transients by large capacitor banks - diyAudio
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Old 7th September 2011, 10:22 PM   #1
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Unhappy improving amplifier transients by large capacitor banks

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.
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Old 7th September 2011, 11:36 PM   #2
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I check smoothing by playing the amp loud and looking at the supply rails.
If they have glitches on them or seriously sag then they need some work.
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Old 8th September 2011, 03:31 AM   #3
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Car power amps use switching power supplies at 25kHz up, and mains-powered amps have 100/120Hz ripple frequency- a huge difference! Car amps don't need as big filter capacitors.
Instead, I find adding capacitance to the 12VDC feed to the (car) power amp helps the most. I use 100,000-250,000uF with thick wiring. I would try that first.
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Old 8th September 2011, 09:46 AM   #4
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ok, if i go with 1 Farad mounted just at 12v input terminal is it going to be much better ????

But would it not depend upon internal resistance of battery Vs ESR ??
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Old 8th September 2011, 10:05 AM   #5
gens is offline gens  Croatia
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1mm squared cable is enough for 10amps, car has usualy 6-idk mm cables

battery gives out over 70 amps

people put capacitators at inputs so the bass gets food, and its not necesary unless you hear a cliping in the bass

other thing is the switching transformer has to try harder when it gets 10V instead of 12
but again, voltage drop is when the amp demands high power, that is the bass usualy(and Ramstein)

so the cap, unless you hear clipping(soft clipping i guess), shud give you a little less heat in your amp, but that little is rly little
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Old 8th September 2011, 10:55 AM   #6
Ola is offline Ola  Estonia
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There is no substitute for microfarads...
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Old 8th September 2011, 03:13 PM   #7
Bigun is offline Bigun  Canada
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I have found that the bass performance of an amplifier is not just a function of the caps on the power rails. I built two Class AB amps, same output stage, same voltage amplification stage, same power supply, same wiring and same speaker with the same source. One had clearly better bass dynamic. The difference was minor, it was a standard LTP input on the one amp and a CFP LTP input on the other. The improved accuracy and local gain boost of the CFP resulted in less distortion on transients and hence better bass. It did also improve the PSRR so I can't completely separate out the effect of adding more capacitance, but I think there's more to transient performance than caps.
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Old 8th September 2011, 08:02 PM   #8
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A car battery cold cranking current can exceed 1000 amps. The capacitors at the amp 12V input aids in regulating the 12V supply from being modulated by the amplifier and the use of long leads from the battery to the amplifier. Because the leads has resistance there will be a volt-drop across each lead when there is current drawn and the larger the capacitor the less modulation would occur since the capacitor is an instant source of energy.

Capacitors cannot replace thick wires but can only help providing the instant energy when needed. And yes it will help in cleaning up the bass performance.

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Old 9th September 2011, 12:17 AM   #9
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Location: Edmonton, AB Canada
Default A car battery is not a really good capacitor

A car battery is not a really good capacitor, it has ESL and dynamic ESR so it is a "mushy" voltage source. If you scope across the battery, you will see: alternator ripple, ignition+injectors+fuel pump noise- all of which can contribute to lack of detail and hazy sound.

The cold-cranking test loads the battery down to 7.2V. Most batteries are about 525CCA but 1000amps= 4.8mohm internal resistance.
15 feet of 10AWG wire is 15mohm, 8AWG is 9mohm.
A 1 farad cap ESR is <2mohm and 2 farad <3mohm. So the cap can definitely help.

Other suggestions to troubleshoot your lack of detail and punch:
Put the Sony amp w/extension cord in your trunk and take a listen.
Change the grounding of your system, as that can have a big effect on car audio quality.
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Old 9th September 2011, 06:29 AM   #10
djk is offline djk
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The cap just smooths things out until the chemical reaction in the battery catches up.

A 1F cap can provide 1A current for 1 Second, that's it.

There are some 1000F caps made for starting cars, they will provide 200A for 5 Seconds.
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