Newbie Grounding question

OniVerde · 18th May 2004, 06:17 PM

Hello all. I recently finished my first DIY audio project by building a pocket headphone amp by following this page.

The amp works fairly well with good sound. However, there's a rather weird problem. When I plug it into my MPIO FL100 mp3 player (has a metalic casing), there's a noise not unlike when one is tuning an AM radio. This only happens when I touch the MP3 player ONLY. If I touch both, the noise disappears. If I change the source to my Sony Discman (plastic casing), I don't hear such noise. Also, if I change the source to a bookshelf shelf CD player, theres a horrible static noise that drowns out the music. What's going on here? Is this a grounding problem?

OddOne · 18th May 2004, 08:40 PM

Sounds like it could very well be a ground problem. Try touching the casings of both items with a length of wire (insulating yourself from all three) and see if the noise is reduced or eliminated.

I was getting horrendous hum out of a receiver when feeding it audio from my computer (I have a HTPC), but adding equal-length ground straps to all relevant pieces of gear cured it completely - I had some major ground-loop action happening.

oO

OniVerde · 20th May 2004, 03:06 PM

There is no noise by doing that. I should also add that the noise only comes when I pick up the mp3 player by itself.

Easyamp · 21st May 2004, 03:04 AM

make sure your amps input ground is connected to you mini plug ground from your fl100. If it is try adding a 100k resistor from your input pin to the ground of the opa input which should be connected to the mini plug ground from the fl100.

Sounds like a simple differential ground plane issue. make sure all your grounds are the same.

Cheers

OniVerde · 21st May 2004, 07:23 PM

Quote:

make sure your amps input ground is connected to you mini plug ground from your fl100

I don't understand. How are they suppose to be connected? It's just one audio jack to another via a interconnect cable.

18th May 2004, 06:17 PM	#1
OniVerde diyAudio Member Join Date: May 2004 Location: Houston	Newbie Grounding question Hello all. I recently finished my first DIY audio project by building a pocket headphone amp by following this page. The amp works fairly well with good sound. However, there's a rather weird problem. When I plug it into my MPIO FL100 mp3 player (has a metalic casing), there's a noise not unlike when one is tuning an AM radio. This only happens when I touch the MP3 player ONLY. If I touch both, the noise disappears. If I change the source to my Sony Discman (plastic casing), I don't hear such noise. Also, if I change the source to a bookshelf shelf CD player, theres a horrible static noise that drowns out the music. What's going on here? Is this a grounding problem?

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18th May 2004, 08:40 PM	#2
OddOne diyAudio Member Join Date: Nov 2002 Location: Earth	Sounds like it could very well be a ground problem. Try touching the casings of both items with a length of wire (insulating yourself from all three) and see if the noise is reduced or eliminated. I was getting horrendous hum out of a receiver when feeding it audio from my computer (I have a HTPC), but adding equal-length ground straps to all relevant pieces of gear cured it completely - I had some major ground-loop action happening. oO

20th May 2004, 03:06 PM	#3
OniVerde diyAudio Member Join Date: May 2004 Location: Houston	There is no noise by doing that. I should also add that the noise only comes when I pick up the mp3 player by itself.

21st May 2004, 03:04 AM	#4
Easyamp diyAudio Member Join Date: Nov 2003 Location: United states	make sure your amps input ground is connected to you mini plug ground from your fl100. If it is try adding a 100k resistor from your input pin to the ground of the opa input which should be connected to the mini plug ground from the fl100. Sounds like a simple differential ground plane issue. make sure all your grounds are the same. Cheers

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