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Old 2nd April 2013, 08:16 AM   #1891
gpapag is offline gpapag  Greece
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[QUOTE=danielwritesbac;3437355
[/QUOTE]

Very good Daniel. Thanks.
Hafler DH-220 amp had this implementation to feed the stages upstream (signal-wise) the output drivers.

George
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Old 2nd April 2013, 11:07 AM   #1892
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Quote:
Originally Posted by AndrewT View Post
What does this mean?
That particular audio amp is not battery powered.
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Where did it come from?
A little gray barn with an SCR, a radiator, and a really big fan.
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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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Last edited by danielwritesbac; 2nd April 2013 at 11:17 AM.
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Old 2nd April 2013, 04:06 PM   #1893
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Originally Posted by gpapag View Post
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.
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Old 4th April 2013, 02:05 PM   #1894
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Diodes only do something useful if you can tolerate more ripple in some places than others. Feeding a whole amplifier through extra diodes achieves nothing, except perhaps to make the PSU more difficult to analyse and design.
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Old 4th April 2013, 08:25 PM   #1895
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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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Old 7th April 2013, 09:08 PM   #1896
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Daniel
It is a 10nF/1000V ceramic disk cap.

I agree with DF96 on the diode in series with the PSU.

George
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Old 8th April 2013, 12:38 AM   #1897
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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.

Last edited by gorgon53; 8th April 2013 at 01:04 AM.
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Old 8th April 2013, 01:19 AM   #1898
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correction:

....voltage the more also the properties of the diodes....
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Old 8th April 2013, 01:36 AM   #1899
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Has anyone any deeper knowledge about the "semiconductor" properties of
electrolytic caps?
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Old 9th April 2013, 03:20 PM   #1900
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Here the link to the psud2
Download

It is a very handy little tool to generate the need info on ripple and current fast .
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