Hi, I'm using esp32 and DFPlayer to play some sound to old set of speakers and amplifiers.
My connection goes from DFPlayer -> AUX connection(Through PCB) -> AUX connector -> RCA adapter right and left.
The RCA goes into the AUX IN of the amplifier(I change it after taking the photo).
I get an annoying bzzz sound when not playing anything.
What can I do to improve this?
Thanks
First thing to try is to improve the connection from the player to the amp. That mess of non-screened wires in your second picture could be to blame. Get a better adapter, something like this
Or replace the whole cable with something more suitable
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You could try twisting the purple and black wires together.
Do each purple with its own black separately.
Here I initially twisted the wires together quite tightly, they then untwist a bit as they relax when released.
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Thanks, I will replace the connection with the adapter sent.
Anything else could be done?
Yes, of course.
If the buzz is not fixed, the next step would be to figure out where the buzz is coming from.
Disconnect the DFplayer and the phono cable from the amp. Can the buzz still be heard? If so, the amp is to blame.
If not, then reconnect the cable but not the DFplayer. Can the buzz be heard? If so, the cable is to blame.
Next, connect something else to the cable connected to the amp, like a smartphone. Try playing and stopping music.
If no buzz is heard in any of these tests, then it is likely that either the DFplayer or the PCB in your photo, or it's power supply are to blame.
How are you powering the PCB? Have you other power supplies you could try?
Most power supplies used with Arduino circuits can introduce noise and buzz into the circuit, but normally this is not a problem for the digital components in the circuit. But analog audio circuits can easily be affected and it can be very difficult to prevent this.
The PCB is powered by a USB that is directly powering the DFPlayer
A USB is a cable, not a power source!
Where is the power coming from? A mobile phone charger? A desktop or laptop PC?
Here is something to try if you have a laptop. Try powering the PCB, thought USB cable, with the laptop powered by the laptop's batteries only, without it's mains charger. Does this affect the buzz?
If so, this also points to the mains charger as the source of the noise.
I have recently been having a similar problem with a Raspberry Pi. I have a USB sound (headphones + microphone) adapter module plugged into the Pi and a microphone connected to that for recording bird calls. But there is a buzz sound in the recordings when I use the official Raspberry Pi USB-C power supply. I found that if I power the Pi from my laptop's USB socket, and the laptop is running off its batteries, the buzz sound disappears. This tells me the source of the buzz sound is coming directly from the Pi power supply, and not being picked up as interference from any of the wiring.
So I powered it from an adapter, I will check which one and will take a stronger one to see if it affects
Yep. Your DFPlayer/Arduino setup is straight DC and your stereo is plugged into AC. Pop another length of wire that grounds your Arduino DC power supply (its GND) to the screw that holds the AC wall plate to the wall (yes, on the front side. You do not need to remove the cover plate or go behind it at all, messing with AC mains. The screw that holds the cover on screws to the junction box which is earthed to the house AC earth).
It should reduce that ground hum significantly, but likely won't get rid of it altogether (wires are antennae after all).
Bonus: good on you to know not to use the PHONO in on the stereo amp. Apart from that; however, the rest are all the same electrically (AUX, CD, Tape) - meaning they are all "line level" which is exactly the voltage level that your DFPlayer headphones out port outputs.
Pop another length of wire that grounds your Arduino DC power supply (its GND) to the screw that holds the AC wall plate to the wall
There is a chassis GND terminal on the back panel (it's in the picture there).
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This one?
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Indeed. I just scrolled up and noticed that (for the antenna). Yeah, give it a go.
I went full out on a the same issue I had using an external phono Pro-Ject preamp with my Yamaha processor/amp (not that brand matters, they all work the same way - just that these are consumer products and not something I made).
I took an old three-prong AC cord (North America 120VAC standard) and disabled the hot and neutral wires, leaving only the earth plug at the bottom connected to anything. Then I soldered on a ring terminal to the end of that wire and ran from the chassis ground of the preamp straight into the APC UPS/power regulator(which already grounds to the amps) where the whole system plugs in to.
I don't hear any hum now unless i turn it up to 11.
That's the one @runaway_pancake is referring to, yes.