Hello,
This is the diagram of my internet radio with Raspberry PI Zero and a TPA3110 class D amp.
The problem I have is that there is a lot of noise in the speaker, especially when there is more activity in the raspberry pi. Without the noise the sound would be very good.
I use a external 12V 4A power adpater like a laptop adpater. I have tested with other power supply and all produce more or less the same noise at the speaker output.
Could you help me to avoid these unwanted noises?
Thanks
This is the diagram of my internet radio with Raspberry PI Zero and a TPA3110 class D amp.
The problem I have is that there is a lot of noise in the speaker, especially when there is more activity in the raspberry pi. Without the noise the sound would be very good.
I use a external 12V 4A power adpater like a laptop adpater. I have tested with other power supply and all produce more or less the same noise at the speaker output.
Could you help me to avoid these unwanted noises?
Thanks
Hello,
This is the diagram of my internet radio with Raspberry PI Zero and a TPA3110 class D amp.
The problem I have is that there is a lot of noise in the speaker, especially when there is more activity in the raspberry pi. Without the noise the sound would be very good.
I use a external 12V 4A power adpater like a laptop adpater. I have tested with other power supply and all produce more or less the same noise at the speaker output.
Could you help me to avoid these unwanted noises?
Thanks
The method I know is "work your way backwards".
Disconnect the DAC from the input of the amplifier and short-circuit the amplifier inputs. Disconnect the LM2596 converter from the output of the 12V supply. Any noise?
If not ->
Connect the LM2596 converter to the output of the 12V supply but keep the DAC disconnected from the amplifier and keep the amplifier inputs short-circuited. Any noise (does the LM2596 converter feed noise back unto the 12V supply line)?
If not ->
Disconnect the LM2596 converter and try to supply the RPI and DAC with a separate 5V supply (if you have any). Remove amplifier input shorts and connect the DAC to the amplifier input. Any noise?
If not, use a separate 5V supply for the RPI and DAC.
If yes, let's discuss the situation.
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Thanks FauxFrench.
This is a sample of noise recorded wiith a smartphone: Noise recording
When I use a separate 5V power supply for raspberry, the noise disappears completely.
But I want put all in a box with a single power supply.
This is a sample of noise recorded wiith a smartphone: Noise recording
When I use a separate 5V power supply for raspberry, the noise disappears completely.
But I want put all in a box with a single power supply.
Last edited:
You should connect all ground lines together ("star grounding").
I had the same issues initially when I set up my (similar) project (all three components - RasPi, DAC and amplifier - powered by the same power source).
Once I joined all ground lines to one central point, the noise disappeared.
BTW, my line out from DAC to amp has ground disconnected - I only have left and right channel signals from DAC to amp (i.e. two wires instead of three - ground is NOT connected).
Try that, and I think your noise problems will be solved.
I had the same issues initially when I set up my (similar) project (all three components - RasPi, DAC and amplifier - powered by the same power source).
Once I joined all ground lines to one central point, the noise disappeared.
BTW, my line out from DAC to amp has ground disconnected - I only have left and right channel signals from DAC to amp (i.e. two wires instead of three - ground is NOT connected).
Try that, and I think your noise problems will be solved.
I believe "den_hr" has given you very good advise. Try following his/her advise in particular cut the ground connection to the amplifier input and avoid the ground loop.
Let's hear if it did not work.
I had a similar problem with a Chromecast Audio. Separate mains cords for the amp and CCA worked but a DC-DC buck or a LM2596 wouldn't.
Either of these work.... I haven't tried the star ground/negative solution.
Get a ground loop isolator
Like this one, some do more basic blocking and will probably screw up bass).: QTX 201.087UK 3.5 mm Jack Ground Loop Isolator: Amazon.co.uk: Musical Instruments
Use an isolating DC-DC converter.
(If you can find one. The one I bought seemed to be around for 6 months then disappeared. 1.5A rating too.)
Yeeco Car Isolated Voltage Regulator DC DC Buck Converter 36V 48V to 5V 2A 10W Step-down Volt Transformer Stabilizer Module Vehicle Power Supply Switch Inverter Board with LED Indicator: Amazon.co.uk: Lighting
Either of these work.... I haven't tried the star ground/negative solution.
Get a ground loop isolator
Like this one, some do more basic blocking and will probably screw up bass).: QTX 201.087UK 3.5 mm Jack Ground Loop Isolator: Amazon.co.uk: Musical Instruments
Use an isolating DC-DC converter.
(If you can find one. The one I bought seemed to be around for 6 months then disappeared. 1.5A rating too.)
Yeeco Car Isolated Voltage Regulator DC DC Buck Converter 36V 48V to 5V 2A 10W Step-down Volt Transformer Stabilizer Module Vehicle Power Supply Switch Inverter Board with LED Indicator: Amazon.co.uk: Lighting
Hello.
First I tried to disconnect the ground from the input cable of the amplifier without success. Noise not only not decreased but it increased considerably.
Then, I have tried to isolate the ground using an old Neutrik Ntl-1 1:1 audio transformer between DAC and AMP. I connected the unbalanced output DAC to pins 6 and 8 and the input AMP in the pins 2 and 4. The noises disappear but I also do not get any sound.
This is the drawing of Neutril Ntl-1:
Does anyone know how the transformer should be connected?
I have not tried yet the central ground solution.
Thanks
No. The DAC only offers a unbalanced output.
First I tried to disconnect the ground from the input cable of the amplifier without success. Noise not only not decreased but it increased considerably.
Then, I have tried to isolate the ground using an old Neutrik Ntl-1 1:1 audio transformer between DAC and AMP. I connected the unbalanced output DAC to pins 6 and 8 and the input AMP in the pins 2 and 4. The noises disappear but I also do not get any sound.
This is the drawing of Neutril Ntl-1:
An externally hosted image should be here but it was not working when we last tested it.
Does anyone know how the transformer should be connected?
I have not tried yet the central ground solution.
Thanks
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Hi trunkline,
The Neutrik transformer is probably 600 ohms, which would be a little low for most DACs. The connection is correct as you had it.
Your original drawing looks like the power for the DAC is coming from the Raspberry board. Maybe it needs its own linear regulator straight from the 12V rail.
Regards,
Rick
The Neutrik transformer is probably 600 ohms, which would be a little low for most DACs. The connection is correct as you had it.
Your original drawing looks like the power for the DAC is coming from the Raspberry board. Maybe it needs its own linear regulator straight from the 12V rail.
Regards,
Rick
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