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Old 15th March 2006, 09:09 PM   #1
orac02 is offline orac02  United Kingdom
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Default Inverter as a power source

Hi
Has anyone out there tried using a DC to AC inverter for the input to thier system?

I recently designed one at work for a customer, to supply a pure sine wave at 230VAC running from a battery. This was supposedly to improve on main bourne noise.

I took it home and ran my CD and amp from it expecting no difference, at least nothing positive.

Much to my supprise there was a distinct improvement, Sound stage, bass and overall clarity.

Has anyone else got any experiences or thoughts?

One thing i have established so far is it sounds bet(probably) with a large battrey. But still better than the mains with a 17 Ah one

Cheers

Steve
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Old 15th March 2006, 09:36 PM   #2
Eva is offline Eva  Spain
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Have you tried it in a blind test where you have to guess which power source is being employed from what you listen and without previously knowing it?

p.s: It's sad to see engineers entering the subjectivist field.
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Old 16th March 2006, 02:50 AM   #3
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Eva,

Perhaps Steve is convinced that it sounds better because of the absence of line noise often found on conventional AC mains.

However, I would be suprised if there wasn't any noise on the output from FRI generated from the DC-DC step-up section.

(The Other) Steve
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Old 16th March 2006, 03:08 AM   #4
Eva is offline Eva  Spain
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I said that because I have been considering such a sine-output inverter design recently and there are a lot of chances to generate gentle RFI with such a circuit. Note that the most harmless part is the DC-DC converter, since the output PWM section is a high voltage class-D amplifier that is forced to perform hard switching of 200V to 400V over a *conducting* diode in each clock cycle (If two phases are used to obtain 230V AC, then hard switching happens twice in each cycle)

The output filter of such converters is also quite a can of worms, because you have to chose between either really bulky output inductors and capacitors, or living with a few volts and amperes of output ripple current and voltage at the switching frequency.

He must have certainly designed a really damn great converter if he thinks that its output contains less non-50Hz harmful stuff than any mains line.
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Old 16th March 2006, 03:23 AM   #5
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Steve,

there is nothing to justify what u experienced except saying that it is your perception or like that''what u wanna hear''.

please subject yourself to a blind test.

SAGAR
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Old 16th March 2006, 03:31 AM   #6
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OOPS! I meant RFI, not FRI. It's getting late here in Michigan. Gonna go to sleep now......
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Old 16th March 2006, 08:22 PM   #7
orac02 is offline orac02  United Kingdom
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Hi
Not that I consider it to be an obvious advantage fron the point of view of unwanted noise, but the inverter switches the 12v to produce the sine wave and is then stepped up through a (relatively) standard toroidal transformer to produce the 230v .Not as Eva suggested it might be done.

Secondly, you are absolutely right , at the moment there is a measurable ripple volltage at the switching frequency present on the ac output. (improvable)

So I expected it to be dreadful as a source for an audio system. Thats why we hadnt bothered putting it in a case (then).

I was still working on the principal of "I dont think this will work but if someone wants to buy it........."

The difference to me seemed large enough to accept the "wot no blind test" to see if anyone else had any ACTUAL experiences.

Off to set up a blind test..!

Cheers
Steve
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Old 17th March 2006, 10:49 AM   #8
orac02 is offline orac02  United Kingdom
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Hi
How about this idea.

Although there is some residual switching frequency ripple on the output this is at a fairly low frequency, the unit is switcing at about 15Khz. At this sort of frequency the input electrolytic capacitors of the amplifier (for instace) will filter it out, as they do the 50Hz ripple.

But

The impedance between the power source (battery) and load
compared with
the impedance between the power source(power station) and the load.
must be less, especially with increasing frequency.

This surely cant be a bad thing!

Thoughts?

Steve
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Old 28th December 2006, 05:11 PM   #9
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Quote:
I was still working on the principal of "I dont think this will work but if someone wants to buy it........."
Do you sell it?
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Old 3rd January 2007, 07:55 PM   #10
KISS is offline KISS  United States
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It doesn't have to be an inverter.

I noticed a major improvement in bass if I use a sine wave voltage regulator. I got a used Sorenson that retails for about $800 for $100.
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