Power Supply Resevoir Size

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I think the question is more complicated than it looks. Depends of PA topology, PS type and so on. I'll give an example.
There was japanese patent from '70s that prevent voltage drop to driver stages. The sound quality improvement is significant. There is more issues. No one rectifier 'love' big capacitors. . . .
339117d1364545116-power-supply-resevoir-size-pa_s.png

You can connect an LM1875 or LM4702 at the spot marked driver stage, and all of the diodes sturdy schottky.
In either case, the high current hookup is the speaker return cable going to the 0v tap on the far left side of your diagram, right at the large caps.
D1 and D2 have prevented C1 and C2 from slowing down C3 and C4. So, by using the diodes, the decoupling has worked.
Kudos!
Yay for not driving with the parking brake on!! :D
It answers Nico's question at post1, post8, post9 about large capacitance sounding dull. Yes, one possible answer is to insert a diode (or a regulator could be used for a more orthodox appearance). So, if you want the fresh sound of small caps, you insert a really creative passive or an active or in fact use small caps.
 
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"Safety-Sized" transformer

With the source of these pulses the bridge rectifier output, shorter length pulses = less power.
But for our simple case, generally, the larger the reservoir capacitance is (or the lower the ripple p-p voltage is), the shorter the pulses are.
So, bigger capacitance = less power. Yes, that's bound to happen when the transformer current, is sized during transformer purchase, below output device capacity, as protection. That's a good thing except. . . That's when it is possible to overwhelm the transformer with too much capacitance and incur that muddy "parking brake" like problem.
Like this:
When the transformer is near maxed out, quite busy both running and smartly protecting the audio amplifier, there's a limited amount of capacitance that it could charge brim full while in this condition.
What is?
Can we relate a transformer in strained condition to a chart with VA and max capacitance?

I end up considering Parallel output devices and monobloc/dualmono builds in order to get enough transformer to charge the power board, without enough transformer to overwhelm the outputs/fuses. So far, that consideration works, but sizing the power board perfectly is still not easy.
 
I am building a power amp using a Meanwell 48V @7.5 amp power supply to power 'Sure Electronics' Digital Amplifier board rated at 300 wpc @ 4 ohms. I expect this rating is probably optimistic but how much capacitance would be recommended for this combination?

As much as you can spring for :D I'm currently using a Meanwell 18V supply for my chipamp (which is an analog one, not classD) and I have a 4 pole LC filter to remove as much as possible of the switching frequency (which I think is around 40kHz). With SMPSUs and classD amps the impedance of the capacitors is at least as important as the total value as they generate huge amounts of HF hash. So be sure to use low ESR types and parallel them up.
 
What does this mean?
That particular audio amp is not battery powered.
Where did it come from?
A little gray barn with an SCR, a radiator, and a really big fan.
Please answer in plain english.
It is possible to get a transformer+bridge rectifier, so busy charging up caps that it does a poor job for anything else, such as running an audio amp rather badly. To fix that problem, I think that we need either more transformer or less caps. If the choice is for more transformer, then I'd like to see more/stronger output devices, which are for raising the current tolerances up high enough to assure safe operation with the more powerful transformer. Tom's recent posts also deal with charge speed, and his posts probably make more sense than my posts. There is such a thing as too much capacitance, which is too slow in some way. I don't have all of the details on that. But, it would be nice to figure out how to size power supplies right on, neither too little nor too much. Charge/recovery speed and that sort of efficiency might be the necessary clues.
 
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Very good Daniel. Thanks.
Hafler DH-220 amp had this implementation to feed the stages upstream (signal-wise) the output drivers. George
Thanks! That looks like a more complete implementation.
I just wanted to mention that, if they're sturdy and efficiency, you can put those diodes like: power supply > schottky > amp board
So, if the particular amplifier, like an lm1875 doesn't support different hookup for predrive, some of the benefit still works if you do the whole amplifier as if it were a predrive.
 
George, I've got a question about that schematic:
For C405 (shows easiest possible way to snub a power supply by confining bridge rectifier noise to bridge rectifier locale, usually seen in integrated amp/receivers as the minimum effort for the radio reception), is that a polyester dip (not box) cap or is it a ceramic disc cap? And, is the value, perhaps, 4.7n, or something else?
 
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OK.
So how does the transformer regulation percentage affect the charging pulse length (or, rather, by how much does it affect it, and how can that be calculated)?

lower regulation percentage means shorter duration and higher current of the charging pulses (RL gets smaller in the RLC-circuit). The better the regulation and the lower the voltage the more the properties of the diodes come into play. Crestfactor can be really high with a transformer regulation below 3%. I had 100A peaks with 10A dc load and a real beefy (2,4% reg) toroid and low voltage drop diodes (BYW93). With a 50A bridge Ip dropped to around 90A.

Duncan made a powersupply simulator called PSUD2 if i remember correctly.
This sim gave me sometimes peculiar results but i would not suspect the formulas because i heard others reporting that the results are suprisingly similar to the real world.
May be you can ask him about the formulas he uses.
 
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