Final doubt on CarlosFM like PSUs ("light" or "complex v3")? - Page 2 - diyAudio
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Old 8th February 2013, 03:01 PM   #11
tent is offline tent  Germany
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ok, will do..

but what makes me also think is that I see very same reasonings and implementations (a la CarlosFM) also in other, let's say professional, or not DIY, style PSUs, like for instance this one from TexasInstruments: http://www.ti.com/lit/an/snaa057a/snaa057a.pdf

it is basically exactly same.. 0.1uF snubbers, 0.1uF+1R snubbers, etc.. ok there is an additional 1uF snubber.. but ok.. and no R3/ resistor here as well..

tent:wq

PS: I speak of unregulated PSU of course..
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Last edited by tent; 8th February 2013 at 03:03 PM.
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Old 8th February 2013, 03:59 PM   #12
JMFahey is offline JMFahey  Argentina
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Yes, I see it.
In fact, they state
Quote:
CS7, CS8 act in conjunction with RS1 and RS2 to decouple the large electrolytic capacitors and reduce impedance
which is true as a concept.
Now I'd love to know what's the measurable or audible effect of that.
As in:
What's the impedance difference between a 10000uF cap and a 10000.1uF one?
What's the ripple difference between a 10000uF cap and a 10000.1uF one?
and so on.

Before you tell me "what about high frequencies"?
Well, I already see a .1uF cap in parallel.
What improvement might make adding a 1ohm resistor in series is beyond me.

Mind you, we are talking *this* , line frequency PSU ; in SMPS it's a whole different World.

As a side note, even if that PSU design "comes from TI", it might very well be the pet idea of somebody working there.
I found it strange, to say the least, their specifying the *Brand* of all components, up to specifying "Panasonic 1 ohm resistors". ??????????????

That said, TI themselves add the following statements, which match my concerns and then some:
Quote:
Many of the capacitors used may not be commercially necessary or may have a minimal effect on performance.
Quote:
For a commercial design, bench and listening test or some other test criteria is
recommended to determine the exact number, size, and type of external components required.
But this is the final "sledgehammer in the head" disclaimers:
Quote:
The values for the different capacitors were not chosen based on extensive bench work or research.
Quote:
The equations and methods to determine optimal
values are beyond the scope of this application note.
Really?
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Old 9th November 2014, 06:02 PM   #13
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Default Isn't this schematic wrong? The negatives from bridges connected

I was understanding that the negative from the top bridge is connected to the positive of the bottom bridge to create the 0 ground reference. all of the Carlos fm schematics on the internet are connecting the negative to the negative? Now the bottom rail has the negative from the bridge connected to the positive of the capacitors?

This doesn't look correct.
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Old 9th November 2014, 07:06 PM   #14
JMFahey is offline JMFahey  Argentina
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Quote:
all of the Carlos fm schematics on the internet
Please post one of them here as an image, otherwise the one we find may not be the one that worries you.
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Old 9th November 2014, 08:33 PM   #15
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Just flip the negative rail bridge.
Every time that schematic is posted somebody comments on the fault and it has been posted many times over the last 10 years. One source is chipamp.com, it is part of the builders guide of their LM3886 kit.
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Old 20th November 2014, 09:04 AM   #16
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On reading the authentic CarlosFM supply, I see that he eq'd his amp via the power circuit, which is an excellent sport, but at the cost of making a one-off that is not generally applicable to any other amplifier. That thing is a custom tuned supply for only ONE amplifier--his.

And that other thing posted from chipamp.com is a marketing purposed made-for-selling product, which is passable and useful for power, but the only thing it does in hi-fi is the marketing. And it does its main job very well. Other than the marketing goodness, it is a very basic simple type supply on an overly large size bright red board, which probably helps for a more attractive appearance. Also, it will block radio reception at far-fringe distance, so obviously those snubbers are in the wrong place and serve only a decorative appearance at best. It does have value, but we need to be aware that it is a well decorated ordinary simple supply.

As for the claim that snubberizing makes a hi-cap supply non-dulling, that's bullsh*t. However, there exists very real and terribly easy ways to do that, such as OsTripper's smart application of fuses (plus cap loaded resistor divider at small signal areas too), AndrewT's well calculated use of cable, and my series diodes, which are ALL low loss series elements NOT entirely located on the power supply board. Snubbers simply don't do the same thing. And certainly not at the power board.


Snubbers don't substitute for series elements. They can assist series elements by loading frequencies selectively (such as making amplifiers immune to speaker cable differences), but they aren't a substitute, and so they do not work as CarlosFM claimed. If in fact it did what it said, the means to function is in making (loading) his series element more effective at hindering the target frequencies, but unfortunately, that other part is undocumented (or at least partially hidden within his cabling and/or layout for his specific amplifier). If I remember correctly, his power supply was in a separate box, in which case, his DC umbilical cable was his series element. And indeed, THAT can be loaded by a snubber. Well, that method is effective and orthodox, but can be overly laborious. I think that it was the Cable, not exactly the snubber, that allowed a hi-cap supply to be non-dulling. That in addition to a high current capable transformer, apparently enough to overwhelm that 1R at the supply.

P.S. I think that both supplies posted are an interesting read and that I will avoid using both of them, because I don't have the application for which they are suited.
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Old 20th November 2014, 09:41 AM   #17
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For more information, here's my latest try at power supplies, in the presence and welcome critique of experts on the Honey Badger thread: diyAB Amp - The "Honey Badger" Feel free to adapt it to twin rectifier for your dual secondaries transformers (which I would rather have used except that the guy I was making it for happened to have a center tap).

Do please also note AndrewT's post diyAB Amp - The "Honey Badger"
Quote:
Originally Posted by AndrewT
A filter MUST have a series element. If there is no series element then it CANNOT be a Filter.
I hope this sheds some light on the snubber questions, because it does apply.
It is my opinion that the series elements did the majority of the work as it pertains to making a high-capacitance supply non-dulling for audio. . . and it is also my opinion that an ideal location for power series element is at the edge of the amplifier board, series to the DC umbilical cable (or in laborious cases IS the cable itself).
Anyway, you can load a series element with a snubber (RC) but it is still true that the series element has done the majority of the actual work and therefore in claims of getting the job done, the credits belong to the series element, not the snubber.

AndrewT's method works perfectly, but I wish he wouldn't finesse the cable for it, since that method breaks my head and/or calculator. There exists easier to figure series elements than that.

It is in this area where CarlosFM failed the documentation although I'm fairly sure that his circuits did produce the output qualities claimed (just not by the means claimed). If we assume, as we should, that the output was of the quality claimed, then indeed there Must have been a series element involved. Unfortunately, the documentation for such is in short supply and not shown on the power supply schematic; and, I guess that is because the main job is on the amplifier board, not the power board.
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Last edited by danielwritesbac; 20th November 2014 at 09:46 AM.
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Old 20th November 2014, 11:17 AM   #18
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I think a part of CarlosFM design is that there is always a series element, if there wasn't you would not need the snubber and that the series element works better with a snubber.
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