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Old 14th October 2013, 03:48 AM   #1
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Default Ungrounded Bluetooth Newbie

I have a ground loop problem with a 50w Sure D amp from PE that occurs when connecting a Sure Bluetooth board and power them from the same 12v power supply.

The amp is fine when run from my iPhone head phone jack, but when the BT board is added I get the 60hz buzz and a lot more.

The buzz goes away if the bluetooth is powered from another outlet.

If it matters, the boards are mounted in a wood speaker cabinet.

I have been reading grounding threads for several hours but can't find a solution that I understand.
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Old 14th October 2013, 11:17 AM   #2
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The solution is simple. Cut the signal ground connection when the bluetooth module is connected. You can do that with a switch.
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Old 17th October 2013, 07:15 PM   #3
xrk971 is offline xrk971  United States
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I had the same issue with the PE BT-1 Bluetooth module when connected to a Sure TPA3110 amp, or a Tripath TA2020 amp. There is a ground loop issue that will only go away when using an isolated DC-DC converter. I used a Murata MEE1S1205SC - fixed the problem. Add a small 47 uF and 0.1uF 50V ceramic cap in parallel at the output to suppress any residual oscillations. If your Sure BT module uses 12V then get the 12V to 12V isolated DC-DC converter.

Invalid Request
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Old 29th November 2013, 09:36 PM   #4
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I'm having the exact same issue and can't find a solution. I just tried an isolated DC/DC converter, and I'm still getting a loud buzz.

I tried the SMAKN converter from Amazon:

Amazon.com: SMAKN Dc/dc Converter 12v Step Down to 5v/3a Power Supply Module: Electronics

Let me know if you figure it out. I've tried everything, and I'm frustrated as hell.
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Old 29th November 2013, 11:23 PM   #5
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by rightshoes View Post
I'm having the exact same issue and can't find a solution. I just tried an isolated DC/DC converter, and I'm still getting a loud buzz.

I tried the SMAKN converter from Amazon:

Amazon.com: SMAKN Dc/dc Converter 12v Step Down to 5v/3a Power Supply Module: Electronics

Let me know if you figure it out. I've tried everything, and I'm frustrated as hell.
Did you try the Murata mee1s1205sc unit I suggested?
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Old 30th November 2013, 12:00 AM   #6
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Quote:
Originally Posted by rightshoes View Post
I'm having the exact same issue and can't find a solution. I just tried an isolated DC/DC converter, and I'm still getting a loud buzz.

I tried the SMAKN converter from Amazon:

Amazon.com: SMAKN Dc/dc Converter 12v Step Down to 5v/3a Power Supply Module: Electronics

Let me know if you figure it out. I've tried everything, and I'm frustrated as hell.
In the first line of the description you can read :"All epoxy sealed containers with Waterproof Housing; Non-isolated"

Cheers ,

Rens
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Old 30th November 2013, 12:49 AM   #7
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I ordered one this afternoon, but I don't exactly how to use it. I assume you solder it to a board along with a capacitor of some sort. Do you have a picture you could post?

I really appreciate your help.
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Old 30th November 2013, 03:13 PM   #8
Rick B is offline Rick B  United States
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Saturnus what is the signal ground connection?
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Old 30th November 2013, 10:54 PM   #9
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Quote:
Originally Posted by Rick B View Post
Saturnus what is the signal ground connection?
I believe it's the audio ground from the bluetooth module to the amplifier. There's the power ground, and the audio signal ground. When I connect the audio ground, then I get no sound whatsoever. If I leave it disconnected, then I get distorted audio. I don't know what Saturnus means by cutting the signal ground with a switch.

I tried an audio transformer between the bluetooth module and the audio inputs on the amplifier board today. It didn't help.
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