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Chip Amps Amplifiers based on integrated circuits

Needing help from experienced builders
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Old 19th May 2018, 08:01 PM   #1
MikeDavidBeats is offline MikeDavidBeats
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Default Needing help from experienced builders

I took on the challenge of building my own amplifier, with 0 knowledge on what I'm doing ( no joke, but I know you want to laugh . My build consists of a 25 -0- 25 650va toroid and two yuan jing 150w x2 amp boards to make a 4 channel amplifier. Where I am at noe after so much back and forth is that with no inputs plugged in the amp is dead silent. Once my inputs are plugged in I get ground loop buzz, but I can't find the loop. I am attaching pictures to see if anyone might be able to spot the problem, or my just have some words of wisdom. Thank you!
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Old 19th May 2018, 09:29 PM   #2
FauxFrench is offline FauxFrench  France
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Location: The mountains, calm and quiet.
For someone claiming to have "0 knowledge on what I'm doing", I have seen much worse.

A few questions:

"Dead silent" with no inputs plugged in" does that mean you have the impression the amplifier does not work?

Have you tried the amplifier with the headphone output from your SmartPhone (floating in potential)?

Where did you ground your chassis?

Have you checked with a voltmeter that the supply voltages on the two amplifier boards are correct?
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Old 19th May 2018, 09:50 PM   #3
MikeDavidBeats is offline MikeDavidBeats
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Thank you, by dead silent I mean with just the speakers plugged in and no audio inputs plugged in there is no him or buzz. That is until I plug the 4 inputs in, then I get very annoying buzz. I tried a rolls he18 buzz off, and it quieted the buzz down, but it's still there.
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Old 19th May 2018, 09:56 PM   #4
MikeDavidBeats is offline MikeDavidBeats
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I did a star ground on a piece of the chassis that extends up and stops vibration from the top cover. It is metal and mounted firmly to the chassis, it is pictured in the middle pic. I only have the toroid, the main power plug, and the amplifier grounds grounded together. Do I ground the shielding of the inputs to the star ground also?
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Old 19th May 2018, 10:18 PM   #5
FauxFrench is offline FauxFrench  France
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Location: The mountains, calm and quiet.
First we need to know if the amplifiers as such work but you create a ground loop when you connect the inputs, or if you just create a buzz sound but the amplifiers actually do not work.
Please try one channel at a time with your SmartPhone as source.
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Old 19th May 2018, 11:10 PM   #6
MikeDavidBeats is offline MikeDavidBeats
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So with amp on and phone used as source. I plugged it into each input and I get no buzz! I haven't tried that yet, but it was nice to hear clear music with no buzz. The source I am trying to get to work is my computer. I make music and the amp powers my monitors. The chain of music signal goes; computer to presonus firebox through firewire, then from the firebox out of the main left right outputs it goes to a minidsp that has two inputs and four outputs that run to the four inputs of my amp. It is so frustrating I can't get it to not buzz.

Last edited by MikeDavidBeats; 19th May 2018 at 11:39 PM.
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Old 20th May 2018, 08:13 AM   #7
FauxFrench is offline FauxFrench  France
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Location: The mountains, calm and quiet.
OK, the amplifier works. Then, try to connect the "mini-dsp" only (buzz?), then "mini-sdp" and "firebox" only (buzz?). Lastly, "mini-sdp", "firebox" and computer which should give buzz.
By going backwards through the signal chain, you better can locate the source of the buzz.
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Old 20th May 2018, 05:35 PM   #8
Kshishtoff is offline Kshishtoff
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It seems to me that the case of the amplifier is grounded with a power network. Try to remove this wire and check if the noise is gone.
And your radiators for the chips are not only installed incorrectly, they are also too small.
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