Quote:
Originally Posted by bikerhifinut
I assumed a DC R of 50 ohms for the chokes.
The capacitor data gives 200 milliohms ESR.
I also ran it as a parallel circuit assuming 1000uF after the choke which would be 2.5H at 50 ohms DC R.
I assume the resustance of the chokes slows down the inrush/charging current to the big capacitors and the ripple is reduced sufficiently to not cause any big effects.
But the question is, does this present any advantage on High transient peaks or does the presence of the resistance of the chokes slow down recharging time sufficiently to cause problems when the amp is responding to high peak levels?
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It's worth doing some basic calculations on the LC smoothing filter. You say 2.5H and 1,000μF, well that gives a resonant frequency of 3.2Hz. (So it will do a really good job of filtering any 100Hz ripple on the reservoir - a reduction of over 900x in fact).
The Q of this filter will be determined by the choke resistance (you say it is 50 ohm), the ESR of the capacitor (0.2 ohm so forget it) and the damping provided by the amplifier (which we don't know). With just the choke resistance, I make it a Q of 1. So the thing will not be prone to a lot of ringing and you will not have to take precautions to avoid oscillations at 3.2Hz. From this point of view, the choke's resistance is A Good Thing.
After a sudden transient demand, you can get a feel for the recharge time - even if the reservoir voltage stayed absolutely constant, the smoothing capacitor will take (very crudely) 1/2 a period to recharge, ie 157msec. Since the Q is 1, the recharge time is determined roughly equally by the DC resistance and by the inductance.
If you increase the smoothing capacitor further, the time will be even longer - but of course with a larger value, the transient demand will have resulted in a smaller voltage drop to recharge from. So recharging time is not the whole story!