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Old 28th October 2011, 07:53 AM   #21
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Quote:
Originally Posted by guitar89 View Post
. . . Using safety ground direct connect to input ground doesn't change anything. . . .
It was already previously connected, else that experiment would have increased the noise.
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Old 28th October 2011, 08:02 AM   #22
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In the mean time, i was studying about those remedies for noise.
Quote:
http://www.diyaudio.com/forums/attac...ood_ground.gif
It lack the prong connection, jsut ignore it
I think i'm going to try 'loop breaker' circuit (also called disconnect network) first, then the above solution. (see if i can make this amp silent)
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Old 28th October 2011, 08:59 AM   #23
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by guitar89 View Post
yay, I have achieve improvement of the noise, recorded and attached link.
The configuration is using a attenuation VR (volume control) between computer output and amplifier input.
Before using this, my computer must configured volume to 5% for normal audio, 15%-20% for booming. above those will deaf my ear.
But now I'm using 100% of computer volume, and control using VR, the noise is significantly reduce ! (difference between 5% and 100% noise) .....................................using safety ground direct connect to input ground doesn't change anything.
you are using your computer to control volume inside your music source !!!!!

Always set the digital volume controls to maximum so that you preserve as much of the digital information as possible.
Attenuate (volume control) the signal as late in the analogue system as possible.
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Old 28th October 2011, 09:09 AM   #24
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Quote:
Originally Posted by AndrewT View Post
you are using your computer to control volume inside your music source !!!!!

Always set the digital volume controls to maximum so that you preserve as much of the digital information as possible.
Attenuate (volume control) the signal as late in the analogue system as possible.
yeah, i agree with you, andrew. Just because it was testing phase, so i use digital volume (i dont want to be deaf)
But it seems attenuation only solution to 'significantly' reduce the noise, but still post a problem (at least won't make my hearing 'motorboating'.
(thiss chip amp is too lousy, using digital volume control and analog control have no different, except the noise)
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Old 28th October 2011, 03:32 PM   #25
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aw... now i have problem.... the ground connection at amplifier side, which is in the PE at the power supply, which is a computer PSU.
How should I incorporate the 'loop breaker' circuit into my PSU (computer's) ?
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Old 28th October 2011, 03:37 PM   #26
AndrewT is offline AndrewT  Scotland
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Do not alter/modify your computer PSU.
You as a beginner are relying on that PSU exporting safe power.

Ensure the computer PSU is properly and securely connected to PE in the mains wiring.

Normally the computer chassis is also connected to the PE. This doubles up the protection to the user in the event that a mains isolation fault develops.

I suggest you too, connect the power importing equipment to PE.

You never insert anything into those equipment to PE connections. NEVER EVER !!

Is that clear?
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Old 28th October 2011, 03:58 PM   #27
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haha, yeah, sure. (its a confirmation question i asked) But how and what should i do solve my problem ? (try to avoid insulation transformer, costly... but will it be effective ?)

It seems more like a oscillation (noise pattern change when the attenuate VR changes) still wondering the real identity of the noise and root cause...
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Old 28th October 2011, 06:40 PM   #28
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Cheapest solution:
A 3 conductor plug for amplifier power supply (enough conductors to include earth ground)
A 2 conductor cord for Amplifier power supply (see link in post 15 for double insulated amplifier power supply)
A 1 conductor cord from earth ground to amplifier enclosure/chassis AND ground loop breaker
A ground loop breaker from earth grounded enclosure/chassis to amplifier power ground

Although I personally favor wooden amplifier enclosures, Despite construction materials, safety requires that the ground loop breaker go from amplifier power ground to earth ground.

Review:
Earth ground connects to amplifier enclosure, aka chassis ground
Earth ground connects to Ground Loop Breaker
Ground Loop Breaker connects to amplifier power ground
Read that again, as if your life depends on it.

You can purchase a suitable replacement ac mains plug at the hardware store. Problem: The plug from the double insulated amplifier power pack linked in post 15 has an insufficient number of conductors. You need a replacement plug that has earth ground so you can cable earth ground to your amplifier enclosure/chassis and to your ground loop breaker.


Please also review related safety materials carefully.
Don't alter the computer.

For a highest quality, less haphazard, answer to your question, here is the list:
Input transformer.
end of list.
That may be safer than the cheapest solution.

Last edited by danielwritesbac; 28th October 2011 at 06:58 PM.
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Old 28th October 2011, 07:24 PM   #29
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Terribly problematic to convey this information because the laptop computer and the car amplifier chip are running from two very similar models of SMPS power supply. These two power packs may be visually similar, but they have different jobs.

I wish to re-iterate: Don't modify the computer. Don't modify the computer's power supply.

When speaking of power supply, I was exclusively discussing the amplifier power supply. It may be necessary to purchase an appropriate power supply for the amplifier.
Again, add the ground loop breaker to the amplifier correctly and cable that ground loop breaker to safety earth ground. . . by upgrading the amplifier with a plug that facilitates using safety earth ground.

For installing the ground loop breaker--If you didn't have up upgrade the amplifier's mains plug (by going to the hardware store to purchase a full size plug that can ADD safety earth ground), then in that case you didn't purchase the right power supply for your amplifier. Please use a compatible power supply for your amplifier.

Attempting to discuss the matter safely, is, in of itself, also hazardous. It would surely be better to use the input transformer option because it is guaranteed to work while other options are not.
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Old 28th October 2011, 07:33 PM   #30
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A very simple option that might work is to change the amplifier's bus ground topology over to a star ground topology.

The matter is definitely where pin 1 attaches to ground, definitely where input loads attach to ground, definitely where input jacks attach to ground, maybe also at pin 4 and maybe also at pin 2. The datasheet is not conclusive as to which pins are supposed to be a member of Signal Star ground.

Signal Star ground is created by adding a resistor of 4 ohms or 10 ohms or similar small amount. One end of that resistor is cabled to Power Star ground. The opposite end of that resistor creates the Signal Star ground.

Please review and compare other amplifier designs that use star grounding. Many of those are highly resistant to problems from computer source.

Last edited by danielwritesbac; 28th October 2011 at 07:37 PM.
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