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I purchased a Lepai LP-2020A+, which is a pretty good little amp for the price, but I've modified it to make it much better and decided it deserved a better casing to look the part, too. So I constructed a little elegant wooden housing for the amp, to get rid of that carry (an attempt to adjectivise the noun car!) appearance.

I assumed the amp's original aluminum housing worked as a sort of Faraday's cage to avoid external electrical signals from coming inside the system, so I covered the inside of the wooden housing with several layers of aluminum tape that's in contact with the original front and rear aluminum panels (which I kept, because they looked rather good on the finished product), thus effectively closing the Faraday cage of sorts.

So everything's generally fine. There's no outside signals getting in, no more noise than there was before, at any rate. However, when one touches the amp (even when one touches the wooden housing, which is strange), normally when one's turning up or down the volume, turning the device off, one gets some electrical noise.

One thing I thought might work was connecting the front and back panels to the device's ground (as you can see in the photo, the potentiometer is already connected to the device's ground). I've tried this, however, and the noise is still there.

I'm wondering if anyone might have any idea of how I can get rid of this noise that only appears when one touches the amplifier.

I'm including a photo of the LP-2020A+'s PCB as it arrived (yes, the noise was there even before I modified the components). Hope someone out there can give me a hand! Any info will be greatly appreciated!

The Lepai LP-2020A+ PCB

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  • \$\begingroup\$ I see a DC barrel jack. Get yourself a ground wire and see what happens if you connect the power supply negative to ground. If you're worried about current loops (I don't know this "brand"), try it with a resistor first. \$\endgroup\$ – Asmyldof Apr 6 '16 at 23:04
  • \$\begingroup\$ Ground loops would be a function of the power brick/wallwart, not the amp. Probably didn't come with a power brick, being made for automotive use. \$\endgroup\$ – Harper - Reinstate Monica Apr 7 '16 at 3:30
  • \$\begingroup\$ /boggle the markings on the PCB. Manufacturer, website, even the product model number. Weird. Clearly not an American design. \$\endgroup\$ – Harper - Reinstate Monica Apr 7 '16 at 3:35
  • \$\begingroup\$ Hello, thanks for your input, @Harper. It did come with a 12VDC 5A power brick, just like one you'd have on a notebook computer. It's true it doesn't have ground included (the brick, it only has two prongs coming out) but it didn't use to make this noise with the original aluminum casing. (And, no, it's not American; it's Chinese... "Made in Bukang"... can't find where that is!) \$\endgroup\$ – QuestionerNo27 Apr 7 '16 at 9:49
  • \$\begingroup\$ Hello, thanks for your input, @Asmyldof. I'll follow your advice and test that out. \$\endgroup\$ – QuestionerNo27 Apr 7 '16 at 9:50
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I have a similar one (Lepai 808), without noise problems anymore. In the beginning the two channels were not at equal volume.The problem was 3 cold joints. Your problem is clearly something with the ground. It seems that is somewere disconnected or not fully working. Try to find where, repair it and no more noise.

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  • \$\begingroup\$ Hello, thanks for the tip. Mine has a similar problem, not a difference in volume, but a much higher voltage output on the left channel (and it would crackle on that side when I turned the volume knob). I was thinking it was just the vol. pot that had bad contact at some points and that was sending out infinite gain into the op-amp, due to the poor designing in that part of the circuit. Where did you find the cold joints? I'm thinking it could be that, too. \$\endgroup\$ – QuestionerNo27 Apr 7 '16 at 9:43

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