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  1. #1
    Senior Member Howard Passman's Avatar
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    Need help with noisy power supply/amplifier issue

    Hi, Unfortunately my SB Radio died recently. It was my second most used SB and I really miss it for outdoor use. I have a few Raspberry pi's so I thought I'd try and make a replacement of sorts. I have a RSP3 with a HiFiBerry DAC+, a 7" touchscreen and a 2.5" hard drive. I would like to put the whole hing in a box with a couple of small speakers.

    I purchased this power supply for the 12v and 5v combo output. It has enough current on the 5 volt out to run everything with the pi and not get the under voltage issue. And of course it has enough output on the 12 volt supply to run the 18Watt amplifier. Here are links to Amazon and both products...

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    Now on to the issue. The 5 volt supply works great and if I run headphones off of the HiFiBerry DAC+, it's dead quiet. The 12 volt supply seems to work well on the amplifier and has no problematic noise unless I try to run both, the RSP3 and the amplifier at the same time. Then I get a high frequency squeal and some clicking noises. The noise does not increase in volume if I turn the volume up, but is loud enough at idle.

    If I run either one off of a separate supply, there is no discernible noise.

    Any help would be greatly appreciated.

    Howard
    Can I go home now?

  2. #2
    Senior Member Jeff07971's Avatar
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    Quote Originally Posted by Howard Passman View Post
    Hi, Unfortunately my SB Radio died recently. It was my second most used SB and I really miss it for outdoor use. I have a few Raspberry pi's so I thought I'd try and make a replacement of sorts. I have a RSP3 with a HiFiBerry DAC+, a 7" touchscreen and a 2.5" hard drive. I would like to put the whole hing in a box with a couple of small speakers.

    I purchased this power supply for the 12v and 5v combo output. It has enough current on the 5 volt out to run everything with the pi and not get the under voltage issue. And of course it has enough output on the 12 volt supply to run the 18Watt amplifier. Here are links to Amazon and both products...

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    Now on to the issue. The 5 volt supply works great and if I run headphones off of the HiFiBerry DAC+, it's dead quiet. The 12 volt supply seems to work well on the amplifier and has no problematic noise unless I try to run both, the RSP3 and the amplifier at the same time. Then I get a high frequency squeal and some clicking noises. The noise does not increase in volume if I turn the volume up, but is loud enough at idle.

    If I run either one off of a separate supply, there is no discernible noise.

    Any help would be greatly appreciated.

    Howard
    Some troubleshooting steps:-

    Is there noise on the amplifier output if the audio input from the pi DAC+ is disconnected ?

    Is the Noise on the DAC+ in the above situation ?

    EDIT:Sorry you have said NO to this.

    If the answer is No to the above have you tried connecting the two commons togther (and possibly to Mains Earth/Chasis) at the PSU ?

    Sounds like a ground loop / ground lifting

    Jeff
    Players: SliMP3,Squeezebox3 x3,Receiver,SqueezePlayer,PiCorePlayer x3,Wandboard
    Server: LMS Version: 7.9.1 - 1503129892 on Centos 7 VM on ESXi 6.5.0U1 on Dell T320
    Plugins: AutoRescan/BBCiPlayer/PowerSave/PowerSwitchIII/Squeezecloud
    Remotes: iPeng8/Orangesqueeze/PC/Jivelite
    Music: 383GB,1269 albums 17756 songs 4381 artists mostly FLACs

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  3. #3
    Senior Member Howard Passman's Avatar
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    noisy power supply

    Thanks Jeff, I haven't tried that. I kind of assumed the PSU commons would be connected internally. I'll give that a shot and let you know.

    Thanks again and have a great day.

    Howard



    Quote Originally Posted by Jeff07971 View Post
    Some troubleshooting steps:-

    Is there noise on the amplifier output if the audio input from the pi DAC+ is disconnected ?

    Is the Noise on the DAC+ in the above situation ?

    EDIT:Sorry you have said NO to this.

    If the answer is No to the above have you tried connecting the two commons togther (and possibly to Mains Earth/Chasis) at the PSU ?

    Sounds like a ground loop / ground lifting

    Jeff
    Can I go home now?

  4. #4
    Senior Member Jeff07971's Avatar
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    Quote Originally Posted by Howard Passman View Post
    Thanks Jeff, I haven't tried that. I kind of assumed the PSU commons would be connected internally. I'll give that a shot and let you know.

    Thanks again and have a great day.

    Howard
    No generally this type of PSU has isolated outputs, then the user can choose.
    It is in the data sheet under "Isolation Resistance" but you do need to know what you are looking for.
    Also in schematic but same applies

    Jeff
    Players: SliMP3,Squeezebox3 x3,Receiver,SqueezePlayer,PiCorePlayer x3,Wandboard
    Server: LMS Version: 7.9.1 - 1503129892 on Centos 7 VM on ESXi 6.5.0U1 on Dell T320
    Plugins: AutoRescan/BBCiPlayer/PowerSave/PowerSwitchIII/Squeezecloud
    Remotes: iPeng8/Orangesqueeze/PC/Jivelite
    Music: 383GB,1269 albums 17756 songs 4381 artists mostly FLACs

    Want a webapp ? See http://forums.slimdevices.com/showth...Webapp-for-LMS

  5. #5
    Senior Member Howard Passman's Avatar
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    noisy power supply

    Hi Jeff, I gave the grounding a shot and no difference at all. The PSU is grounded and I am using a 3 prong plug. so everything should be grounded properly.

    It's odd to me that it doesn't do it if I power the amplifier separate from the rest of the stuff.

    Thanks again,

    Howard



    Quote Originally Posted by Howard Passman View Post
    Thanks Jeff, I haven't tried that. I kind of assumed the PSU commons would be connected internally. I'll give that a shot and let you know.

    Thanks again and have a great day.

    Howard
    Can I go home now?

  6. #6
    Senior Member Jeff07971's Avatar
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    Quote Originally Posted by Howard Passman View Post
    Hi Jeff, I gave the grounding a shot and no difference at all. The PSU is grounded and I am using a 3 prong plug. so everything should be grounded properly.

    It's odd to me that it doesn't do it if I power the amplifier separate from the rest of the stuff.

    Thanks again,

    Howard

    So both the commons are connected to Mains (Chasis) Earth ?
    Players: SliMP3,Squeezebox3 x3,Receiver,SqueezePlayer,PiCorePlayer x3,Wandboard
    Server: LMS Version: 7.9.1 - 1503129892 on Centos 7 VM on ESXi 6.5.0U1 on Dell T320
    Plugins: AutoRescan/BBCiPlayer/PowerSave/PowerSwitchIII/Squeezecloud
    Remotes: iPeng8/Orangesqueeze/PC/Jivelite
    Music: 383GB,1269 albums 17756 songs 4381 artists mostly FLACs

    Want a webapp ? See http://forums.slimdevices.com/showth...Webapp-for-LMS

  7. #7
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    Quote Originally Posted by Jeff07971 View Post
    So both the commons are connected to Mains (Chasis) Earth ?
    The data sheet for the power supply in the link above shows the DC output OV terminals are common and not connected to mains earth.

    Sent from my SM-G900F using Tapatalk

  8. #8
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    Quote Originally Posted by Jeff07971 View Post
    No generally this type of PSU has isolated outputs, then the user can choose.
    It is in the data sheet under "Isolation Resistance" but you do need to know what you are looking for.
    Also in schematic but same applies

    Jeff
    I think Isolation resistance is normally between input and output not between two outputs.

    Sent from my SM-G900F using Tapatalk

  9. #9
    Senior Member Jeff07971's Avatar
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    Quote Originally Posted by slartibartfast View Post
    The data sheet for the power supply in the link above shows the DC output OV terminals are common and not connected to mains earth.

    Sent from my SM-G900F using Tapatalk
    I was asking if he had connected Commons to Earth
    Players: SliMP3,Squeezebox3 x3,Receiver,SqueezePlayer,PiCorePlayer x3,Wandboard
    Server: LMS Version: 7.9.1 - 1503129892 on Centos 7 VM on ESXi 6.5.0U1 on Dell T320
    Plugins: AutoRescan/BBCiPlayer/PowerSave/PowerSwitchIII/Squeezecloud
    Remotes: iPeng8/Orangesqueeze/PC/Jivelite
    Music: 383GB,1269 albums 17756 songs 4381 artists mostly FLACs

    Want a webapp ? See http://forums.slimdevices.com/showth...Webapp-for-LMS

  10. #10
    Senior Member Jeff07971's Avatar
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    Quote Originally Posted by slartibartfast View Post
    I think Isolation resistance is normally between input and output not between two outputs.

    Sent from my SM-G900F using Tapatalk
    If you read it it says Input to Output, Input to frame ground, output to frame ground are all 100M, so output to output is at least 100M

    As I said you have to know what you're looking at

    Jeff
    Players: SliMP3,Squeezebox3 x3,Receiver,SqueezePlayer,PiCorePlayer x3,Wandboard
    Server: LMS Version: 7.9.1 - 1503129892 on Centos 7 VM on ESXi 6.5.0U1 on Dell T320
    Plugins: AutoRescan/BBCiPlayer/PowerSave/PowerSwitchIII/Squeezecloud
    Remotes: iPeng8/Orangesqueeze/PC/Jivelite
    Music: 383GB,1269 albums 17756 songs 4381 artists mostly FLACs

    Want a webapp ? See http://forums.slimdevices.com/showth...Webapp-for-LMS

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