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Old 15th January 2004, 03:44 AM   #21
cowanrg is offline cowanrg  United States
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Default Re: The Original And Best Whopper ???..........

now THAT'S something that makes sense!

Quote:
Originally posted by mrfeedback
"The Original WHOPPPER® Sandwich has been doing its thing since 1957. It's a fire-grilled classic and everything you would expect from a great-tasting burger – 1/4 pound of beef, red ripe tomatoes, crisp lettuce, creamy mayonnaise, ketchup, crunchy pickles and onions all on a freshly baked bun. Add extra ketchup and HAVE IT YOUR WAY®."
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Old 15th January 2004, 03:55 AM   #22
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The biggest lie (whopper) is suggesting that eating those things is good for you !!!.

Eric.
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Old 15th January 2004, 03:55 AM   #23
grataku is offline grataku  United States
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Seems to me that the problem could be solved to first order by NOT having the rectifier on one side and the output on the other. I don't get what the C(RCR)nC arrangment is doing.
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Old 15th January 2004, 03:56 AM   #24
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Ime, taming psu resonances is always a sonically good thing.

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Old 15th January 2004, 04:12 AM   #25
cowanrg is offline cowanrg  United States
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i know im an idiot with electronics, but wouldnt it make sense to just use two caps? or, (thinking outside of the box, and i shouldnt even be allowed near the box), what if you had multiple rectifiers with pairs of caps after?
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Old 15th January 2004, 04:19 AM   #26
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Quote:
Originally posted by Lars Clausen
Just wanted to add the schematic to our solution discussed. So easier to follow.

Sorry the text is in Dansih language, but the schematic should speak for itself.

The resistors ensure that the charging spike is equally distributed over the entire capacitor bank, and also equally discharged from all 4 capacitors to the amplifier.

I will just emphasize one point, so everyone in here can understand, also Fred: Only the positive side of the power supply is shown here on this schematic. There need also be a corresponding negative side of this power supply circuit to make it work properly.

Wouldn't this circuit just increase the ESR of each cap? Then to account for the increased ESR you have to put a high quality bypass cap on the whole network?


Scott
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Old 15th January 2004, 04:30 AM   #27
angel is offline angel  Norway
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As to the bit about raising the ESR, well, not really, but it raises the net resistance of the power supply, although by an insignificant amount, further mitigated by the small, high quality cap on the output.

More relevant, it raises the resistance seen by HF noise, which might otherwise just 'bounce' past the caps, never even seeing a path to ground, due to the slowness of the caps. Now the HF will at least 'see' a small series resistance, then a fast cap, forming a good low pass filter.

Also, raising the resistance, without affecting the reactance, yields a lower Q factor, which means you are damping power supply resonances.

The slightly raised rise-time also serves to protect the rectifier, as well as reducing noise spewed back onto the mains.

For class A/B amplifiers, where the average power may be significantly lower than the peak power, you might want to use such a supply, and use higher value input resistors (less load on the presumably small transformer, which is sized based on average load), while retaining the low value output resistors, for better transient response.

As to just using two caps, that makes sense, if they are fast enough. Unfortunately, the larger a cap is, the slower it tends to be.

Of course, there are many solutions to this problem. I'll just list a few.

(A) Go with what Lars did, and build a power supply with controlled resonances and better load sharing, using many small, fast caps.

(B) Use a polypropylene cap instead. Unfortunately, they come in small capacities (I've seen none bigger than 330uF), so you would have to use high voltages to exploit their storage capacity, and a switcher to step the voltage down.

(C) Use stages that consume a constant amount of current, such as differential stages (e.g. the Son of Zen or BZLS). These should be indifferent to the high frequency capabilities of the power supply. In fact, slow caps might help the CMRR at high frequencies, as any imbalance tends to be degenerated by the low compliance of the supply.

(D) Use full or partial shunt regulation of your supply, so that your HF response is dependent on the shunt circuitry, rather than the slow caps. For example, use a depletion mode FET from the rail to ground, with a resistor on the gate, and a cap from the rail to the resistor.

(E) Do what Lars did, but parallell hundreds of small caps instead.

(F) Do what Lars did, but switch the resistors for inductors instead. Select the values, including the Q of the inductor, carefully. You must be especially careful of the output, as you don't want ringing from interactions between the smaller, fast cap, and the inductor, during load variation.

(G) Any combination of the above.

(H) Forget about it, and just build an "audiophile" grade switch mode power supply, throwing such concerns as 'efficiency', 'low cost', and 'cool operation' out the window.

Just my 2 cents.
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Old 15th January 2004, 04:31 AM   #28
cowanrg is offline cowanrg  United States
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could someone simply and plainly explain what a switching power supply is? ive heard it a million times, and all i know is its supposed to be bad for audio and computers have them.
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Old 15th January 2004, 04:47 AM   #29
angel is offline angel  Norway
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The term 'switching power supply' refers to a different kind of power supplies from what you are used to (those are called 'linear supplies')..

There are a lot of audiophile myths about switching supplies being bad, and if you want to dispel them, go have a listen to some of the high end products from e.g. Linn, that use switching supplies. Theirs are so good they even eliminate any gains from filtering or fancy power cables, which is hard to do, regardless of the kind of supply you use.

Basically, a computer grade supply is bad because it is built from overly cheap components, and designed to save money.

As to how switching works, it depends. The most basic thing is, you chop up the alternating current from the mains into pulses, that are deposited into capacitors as usual. The number of pulses per second, or their energy content, or both, can be shaped in a number of ways, allowing good regulation, and ideal mains loading.

Good results can be achieved through hard work and good engineering. Bad results are easily achieved by cutting corners or bad engineering. Regardless of whether you use switched power supplies, or linear power supplies. The skill threshold for using the switching technology successfully just happens to be a bit higher.

It is simple enough to build hybrid supplies, though, where a transformer, rectifier, and cap, provide a high voltage DC supply, and some transistors, resistors, an inductor, a capacitor, a diode, and a voltage reference (e.g. zener), let you step down the high voltage to a lower, more useful voltage.

Of course, any kind of switching process generates noise, and you have to deal with it. Which is a topic that is common to switched and linear supplies, frequently addressed with large inductors, fast capacitors, regulation, and so forth.

Hope this clarifies.
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Old 15th January 2004, 04:47 AM   #30
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Quote:
Originally posted by cowanrg
could someone simply and plainly explain what a switching power supply is? ive heard it a million times, and all i know is its supposed to be bad for audio and computers have them.
Look here: http://henry.fbe.fh-darmstadt.de/smps_e/smps_e.asp
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