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Chip Amps Amplifiers based on integrated circuits

Grounding help Circuitbasic LM3886 and Mark Johnson PSU
Grounding help Circuitbasic LM3886 and Mark Johnson PSU
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Old 14th May 2020, 12:58 AM   #11
Dneu2011 is offline Dneu2011  United States
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Join Date: Jul 2017
I added the Ground Loop Breaker and 1NF ceramic across the rca ground and chassis.

It seems it took care of some noise but I noticed I am mostly picking up radio frequencies now. If I move around my speaker and power cables I can eliminate the radio channel but it seems like the speaker cables are acting as antennas and there is still some buzzing.

Any ideas on what to try next?
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Old 14th May 2020, 07:29 PM   #12
farley is offline farley  United States
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Join Date: Oct 2011
Location: Texas
I'm no expert, only a hobbyist at this, but some things I would investigate:

1. There is a long yellow wire extending from the power supply filter PCB to the safety ground connection. If that wire is supposed to connect the filter PCB ground to the chassis, can it be shorter and connect to the mounting plate right at the power supply filter PCB?

2. There are long grey wires that appear to come from the audio input jacks. If those are the audio input feed to the amp boards, make them much shorter and use as direct path as possible from the input jacks to the amp audio input connections.

3. There appear to be a couple of black wires extending into the air from the filter PCB. Is there a reason those are there?

4. Does the radio interference go away or lessen when the case is closed up and screwed together?

5. The speaker wires and DC feed wires to the amp boards are intermingled. Is it possible to separate them?

Overall, make all connections only as long as they need to be to get from their start to their finish (don't make them taught though).
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Old 17th May 2020, 10:42 AM   #13
Mark Whitney is online now Mark Whitney  Netherlands
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Join Date: Feb 2013
Location: Netherlands
This is what I would do:

Place a 1R resistor and 2 diodes back to back (HBR) between C4 and C6 on the underside of the amp boards.

Connect the speaker return/ground to C6 topside.

Connect the power 0V/ground in a Y between the two amps and PSU.

Place a GLB between chassis and Power 0V/ground. Use a 10R >5W resistor and 35A Bridge Rectifier.

Connect the PE to chassis.
Regards Mark.
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Old 18th May 2020, 08:44 PM   #14
nasifimtiaz is offline nasifimtiaz  Bangladesh
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Join Date: Dec 2015
Location: Sylhet, Bangladesh
I think you missed installing the Thiele Networks at speaker terminals. Thiele network reduces oscillations caused by capacitive loads, usually due to long speaker cables. It also prevents radio frequencies picked up by the speaker wires from getting back into the amplifierís inverting input through the feedback loop.
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