I have a car amplifier.... the volt that out from power supply is 33V+/- (66V) and i have 6600uF per side (33-0) 13200uF TOTAL.
if i put more 47000uF per side... what it will do ??
thanks!
tamir
if i put more 47000uF per side... what it will do ??
thanks!
tamir
Hi DjDj BASS AMP said:
As far as I can think, not much.
You'll have a bigger inrush current, that is more current will flow at startup to load the caps, and maybe the Bass will improve a bit.
/Hugo 🙂
Re: Re: Up-Grade My Car Amplifier
OK Thanks! Hugo....
and what about a 1,000,000uF (4700uF 25V x213 caps) in the input power of the amp ??
Tamir.....
Netlist said:
OK Thanks! Hugo....
and what about a 1,000,000uF (4700uF 25V x213 caps) in the input power of the amp ??
Tamir.....
Re: Re: Re: Up-Grade My Car Amplifier
No seriously, you should ask the car forum, but to me it seems useless. Build yourself a Pass amp with these caps 😉
/Hugo 🙂
This will be a nice buffer to start the engine when your battery fails. 😀Dj BASS AMP said:
No seriously, you should ask the car forum, but to me it seems useless. Build yourself a Pass amp with these caps 😉
/Hugo 🙂
You can compare the effect of the capacitors before and after the power supply by calculating the amount of energy they store
E = .5 * C * V^2
1 Farad charged to 12V will be storing 72 Joules
To get this energy stored at 66V youll need :
72 = .5 * C * 66^2
C = 72 / (.5*66^2) = 34,4mF
So, 68.000uF per supply rail will have equal or better effect than 1F at 12 V [actually better because peak current in the power supply will be greatly reduced and so voltage drop]
The effect of all this capacitance is to gently smooth the current drawn from 12V supply, reducing instantaneous voltage drops and losses in the power supply
Adding more capacitance would be a overkill, actually 2x 33.000uF should do a great job reducing voltage drops in 12V supply since current from the capacitors is drawn at 2*signal_freq and 33.000uF have 0.08 ohms plus ESR at 60Hz [30Hz signal], much lower impedance than the power supply itself
Most amplifiers have a gentle soft-start, slowly ramping the duty cycle of the power supply from 0% to maximum, so inrush current rarely is a problem [you may put a bigger soft-start capacitor or resistor in the control IC to get even slower soft-start]
NOTE : I'm assuming the usual car-audio amp whose channels draw current from opposite supplies when driven with same polarity signal, and the usual stereo or bridge configuration where signal is the same for both channels at LF [ie: power drawn at 2*F from each supply]
E = .5 * C * V^2
1 Farad charged to 12V will be storing 72 Joules
To get this energy stored at 66V youll need :
72 = .5 * C * 66^2
C = 72 / (.5*66^2) = 34,4mF
So, 68.000uF per supply rail will have equal or better effect than 1F at 12 V [actually better because peak current in the power supply will be greatly reduced and so voltage drop]
The effect of all this capacitance is to gently smooth the current drawn from 12V supply, reducing instantaneous voltage drops and losses in the power supply
Adding more capacitance would be a overkill, actually 2x 33.000uF should do a great job reducing voltage drops in 12V supply since current from the capacitors is drawn at 2*signal_freq and 33.000uF have 0.08 ohms plus ESR at 60Hz [30Hz signal], much lower impedance than the power supply itself
Most amplifiers have a gentle soft-start, slowly ramping the duty cycle of the power supply from 0% to maximum, so inrush current rarely is a problem [you may put a bigger soft-start capacitor or resistor in the control IC to get even slower soft-start]
NOTE : I'm assuming the usual car-audio amp whose channels draw current from opposite supplies when driven with same polarity signal, and the usual stereo or bridge configuration where signal is the same for both channels at LF [ie: power drawn at 2*F from each supply]
math’s and math’s, all over the place...
Sometimes it's worthwhile to keep a thread on top 😉
/Hugo 🙂
Well Dj, there you got it from an expert.Eva said:
Sometimes it's worthwhile to keep a thread on top 😉
/Hugo 🙂
Hi Eva Be carefully wiht the capacitors.
Your mathematical it´s right, but it not a real wordl.
I made one amplifier 50W Clase A with 470000uF for rail.
If you, calculate the filter in low frecuencyt and the amotiguation factor is brutal but is not the best factor when us listened the music, eva the music is not one real frecuency generartion , is a complex wave you have treat each as it is , and depend of the each capacitors not only the static response versus the frecuency.
For example I use Black Gate capactors of 1/100 versus anothe mark
and I sure that the Black Gate Capacitors was winer that other marks with the 100/1 more Capaicior.
Jesús
E = .5 * C * V^2
1 Farad charged to 12V will be storing 72 Joules
To get this energy stored at 66V youll need :
72 = .5 * C * 66^2
C = 72 / (.5*66^2) = 34,4mF
Your mathematical it´s right, but it not a real wordl.
I made one amplifier 50W Clase A with 470000uF for rail.
If you, calculate the filter in low frecuencyt and the amotiguation factor is brutal but is not the best factor when us listened the music, eva the music is not one real frecuency generartion , is a complex wave you have treat each as it is , and depend of the each capacitors not only the static response versus the frecuency.
For example I use Black Gate capactors of 1/100 versus anothe mark
and I sure that the Black Gate Capacitors was winer that other marks with the 100/1 more Capaicior.
Jesús
E = .5 * C * V^2
1 Farad charged to 12V will be storing 72 Joules
To get this energy stored at 66V youll need :
72 = .5 * C * 66^2
C = 72 / (.5*66^2) = 34,4mF
Re: Re: Re: Up-Grade My Car Amplifier
No need to parallel two hundred "small" caps... there are 1 Farad caps commercially available for just for that purpose.
But the premise for using them is a bit different. The idea is that when a high power car amp hits 100 amp peaks, the voltage at the amp's terminals drops because of source resistance in the power system. With unregulated internal power supplies, the amp's power also drops during those peaks. Holding the input voltage steady with a huge cap can give the amp the juice it needs to handle those peaks.
Just 50 milliohms of source impedance (alternator, battery, wiring, fuses, connections etc) is a 5 volt drop at 100 amps. A 1 Farad cap on the other hand:
i = C dv/dt
1 Farad will lose 1 volt when supplying 100 amps for 10 millisec.
The usefulness of big caps in car audio systems is endlessly debated in the car audio foums. The consensus is you're much better off eliminating the source impedance by using a heavy duty alternator and bigger wires.
Dj BASS AMP said:
No need to parallel two hundred "small" caps... there are 1 Farad caps commercially available for just for that purpose.
But the premise for using them is a bit different. The idea is that when a high power car amp hits 100 amp peaks, the voltage at the amp's terminals drops because of source resistance in the power system. With unregulated internal power supplies, the amp's power also drops during those peaks. Holding the input voltage steady with a huge cap can give the amp the juice it needs to handle those peaks.
Just 50 milliohms of source impedance (alternator, battery, wiring, fuses, connections etc) is a 5 volt drop at 100 amps. A 1 Farad cap on the other hand:
i = C dv/dt
1 Farad will lose 1 volt when supplying 100 amps for 10 millisec.
The usefulness of big caps in car audio systems is endlessly debated in the car audio foums. The consensus is you're much better off eliminating the source impedance by using a heavy duty alternator and bigger wires.
so what will be batter?? 1F connect to the amp??
or 2x 33.000uF after the power supply of the amp??
thanks!
or 2x 33.000uF after the power supply of the amp??
thanks!
Dj BASS AMP said:
better (or worse) in what regard?
you can always argue that 10000000F is better than 1F. but does it make a difference in real life? if not, why should we care?
Equivalent energy storage placed after the power supply allways gives lower voltage drop to the amplifier circuit
Even if the 1F capacitor is showing .004 ohms at 60Hz, the power supply of a typical amplifier will apear as .030 ohms or so in series with the capacitor so the voltage drop inside the amplifier will be higher when energy storage is before power supply
Alternators operate as pulsed current sources whose amplitude is very slowly controlled by the regulator [amplitude depends on the magnetization of the rotor, whose inductance is huge], so the output impedance of an alternator is almost infinite at audio frequencies
Lead-acid batteries can only source some current when its cell voltage is made less than 2 to 2.1 volts, so when you put 20-50A of load to the 12V system, even if the multimeter measures more than 13 Volts, the instantaneous voltage will be oscilating between less than 12V between alternator pulses and 15V during the crest of the pulses
The only way to get DC voltages [not pulsed] higher than 12 V is to add some storage capacitance so alternator output could be truly rectified
An oscilloscope, a car and sompe patience will help to understand all these facts
Of course, don't expect car audio people to get an oscilloscope and have enough electronics knowledge to do some serious findings about this
Also, it's a very bad idea to have huge currents at 2*signal_freq flowing thorugh 5-10 meters of 12V supply wires because this produces huge magnetic fields and lots of magnetic induction on signal lines and speaker wires [the induced signal will be pure distortion due to its 2*F nature and can be measured with a simple loop of wire connected to the scope probe]
Again, don't ask car-audio people about magnetic fields or induction 🙄 or about twisting 12V supply wires to reduce it
Even if the 1F capacitor is showing .004 ohms at 60Hz, the power supply of a typical amplifier will apear as .030 ohms or so in series with the capacitor so the voltage drop inside the amplifier will be higher when energy storage is before power supply
Alternators operate as pulsed current sources whose amplitude is very slowly controlled by the regulator [amplitude depends on the magnetization of the rotor, whose inductance is huge], so the output impedance of an alternator is almost infinite at audio frequencies
Lead-acid batteries can only source some current when its cell voltage is made less than 2 to 2.1 volts, so when you put 20-50A of load to the 12V system, even if the multimeter measures more than 13 Volts, the instantaneous voltage will be oscilating between less than 12V between alternator pulses and 15V during the crest of the pulses
The only way to get DC voltages [not pulsed] higher than 12 V is to add some storage capacitance so alternator output could be truly rectified
An oscilloscope, a car and sompe patience will help to understand all these facts
Of course, don't expect car audio people to get an oscilloscope and have enough electronics knowledge to do some serious findings about this
Also, it's a very bad idea to have huge currents at 2*signal_freq flowing thorugh 5-10 meters of 12V supply wires because this produces huge magnetic fields and lots of magnetic induction on signal lines and speaker wires [the induced signal will be pure distortion due to its 2*F nature and can be measured with a simple loop of wire connected to the scope probe]
Again, don't ask car-audio people about magnetic fields or induction 🙄 or about twisting 12V supply wires to reduce it
- Status
- Not open for further replies.