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Old 11th January 2013, 10:00 PM   #91
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Marce I assume you mean domestic HVAC, commercial and industrial HVAC usually has power factors ranging from 0.85 for small unit to 0.94 for large units, this is a plain lagging power factor. The exception is the inverter type which has plenty of harmonics, there is a push to reduce the harmonic content of mains powered equipment.
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Old 11th January 2013, 11:33 PM   #92
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The computer I'm using now use to have a bad hiss from the on board audio and the video was fuzzy with less contrast and colours when using the VGA connection to the monitor compared to the DVI connection, I changed the power supply from a cheap 350w no name type brand to a cheap 450w no name type brand because it had a bigger quieter fan. Now the audio is as good if not better as my cd player, there is also now no difference between the VGA and DVI video quality.

So it is possible for a power supply to make a difference, but in my case it was one cheap switch mode power supply vs another cheap switch mode power supply that made the difference
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Old 12th January 2013, 05:09 AM   #93
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Quote:
Originally Posted by kp93300 View Post
I made this linear power supply based on LM 338 with pretracking regulator and the regulated output is 11.8 V. I use a 10 V zener to reg the output.
The trans is 13.5 V ac out and at least 400W capability and is source from an old medical laser printer.
I made it to power an atom based pc which utilize a 60 W smps.

The reg power supply will not power on the pc .

What are the special requirements to use a linear power supply for pc use ??

pointers are most welcomed.

thanks
kp93300
A linear supply for a computer is a difficult project. Even if your computer has no switching supplies on the motherboard (low probability) just the noise from all the digital activity is LOUD. If you have a scope just connect a wire 'pigtail' to the probe and wave is around the mother board. There is all sorts of noise.

Then when you calculate the efficiency and the required headroom for low line Voltage and the waste heat you'll find it borders on insane. And after all that work, will it get quieter than what you have now? The board manufacturer of my PC (Gigabyte) claims 108dB. That's hard to verify but I'm certain it's north of 90. The PSU will also operate at 67 Volts as it did when one of the 3 phases failed in my neighborhood last year. It will also go up to 240Volts with no user input and does power factor correction to 0.98. It's virtually certain your linear supply would not function below 90 Volts and realistically 105 might be the practical lower limit.

I believe there are projects that would give more satisfaction with less work and money.

Here's one for you that could quiet down your analog audio output, REALLY work and is quite simple. I know this works as I used it in my car years ago to add a portable CD and power it from the car - no batteries - that's too easy.

Build a balanced line receiver (Burr-Brown INA134 or Analog Devices SSM2141) and use it to receive analog audio from the PC. Tie the two '-' inputs to the ground from the PC output cable and the '+' inputs to the signal. Any noise on the ground gets subtracted out of the signal. LOTS cheaper and more effective than linear PSUs. Never fight Ohm's law. Use it to your advantage with differential amplifiers.

G
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Old 12th January 2013, 06:50 AM   #94
qusp is offline qusp  Australia
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yep, pretty much what I said on Page 1, but it seems they are determined to fly in the face of adversity/absurdity
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Old 24th January 2013, 11:38 AM   #95
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Quote:
Originally Posted by marce View Post
The digital audio equivilent of the Higson particle...
I like the 'Dark Bits' name, it conjours up images of an anti audiophile demon, the Darth Vader of digital audio design, and to quote said gentleman...
"I find your lack of faith disturbing."
and as I am in a rather silly mood, another:
"I sense something, a presence I've not felt since.......I swapped my linear supply for a dark SMPS"
I've heard rumors of a new Intel 666 processor / chipset...
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