Bluetooth Speaker build w. Pi Zero W + Phat DAC - Sound problems

Hello Pimoroni community,

I am very excited to become part of this great community. I have been an avid reader but never actively interacted or contributed yet.

For my debut I am trying to build a Bluetooth Speaker with Pi Zero W and Phat DAC.

I have a male header on the Pi Zero and a female header on the Phat DAC.
I have also soldered cables on the Phat DAC for the audio output. I then try to use a VMA408 class-D AMP ( which should be similar to the Adafruit MAX98306 ( The AMP then powers one 8Ohm/3W speaker.
So actually I am looking for a mono sound source but have just ignored that for now. Not sure if this might cause my issues.

I get the Rpi 0 to be discoverable by bluetooth and open to connect to. When I connect my phone to it I can play audio via Spotify, etc.

The problem I am encountering now is, that I hear quite some noise, hissing, etc. possibly CPU sound and I am clueless how to get rid of it. I was suspecting a ground loop but I am not really sure about that as I only have one power source, the USB cable (I have an Adafruit powerboost to make it portable but leave that out for simplicity for now).

Can anyone point me toward the right direction to get rid of the noise? Did I make a mistake with the wiring? Is there interference issues? Do I have a ground loop and if so how can I get rid of it.

Alternatively I was also thinking of a software fix, possibly cutting of any connection to the amp/speaker until an actual signal is coming from my phone.

I have attached a few pictures of my setup and are happy to share my code if that helps.

Let me know if you have questions and thanks for any reply.


I have a background in electronics, but I’m still not sure what’s going on to be honest.
One thing I would do is make my wires as short as possible and try to reduce the number of alligator clips if possible. Direct solder connections with wires.
Just throwing this out there, but a pHat Beat might be a better option. It has an amplifier built in and is also stereo sound. You can turn the VU meter off to save power. It also has a switch to select mono out, and friction fit connections for the speaker(s). It may simplify things for you.

I have one in my Pirate Radio setup and I am very happy with it.

Just had a second look at your pictures. Where did you get that speaker from? Something doesn’t look right with it? It looks like the cloth is missing or something? I’d for sure try a different speaker.

I think you’ll find that is a real speaker but with a transparent mylar (plastic) cone instead of the traditional black paper/cloth.
It could do with a baffle though to get some sound out of it.


Yeah actually the pHAT BEAT looks like a quite good solution.
The reason why I choose the Phat DAC was that I am actually trying to use an old radio as a speaker which has a built in potentiometer and amplifier that I still wanted to use. I got it work but had the same issue with the noise.

I might have another go at it with shorter wired actually soldering everything together and removing the crocodile clamps. I tried to get it up and running before finalising the wiring but if that might cause the problem, I will try to fix it.

The speaker is really bad, just salvaged the one from somewhere but I already tried a couple of others and always had the same issue with the noise. I can try to record or take a video of it as well.

Let me know if you have any other tips.


Ok, if you’ve tried other speakers, it not “that” speaker. It may be digital noise pickup, that usually changes frequency though. And stops and starts etc. It wouldn’t hurt to double check you soldering. Look for bridged pads, etc.

I have a Pi 3B where the analog out feeds an Adafruit stereo amplifier beak out board. I wasn’t long wiring in a volume control to make adjusting it easier and quicker.

The pHat Beat has buttons for adjusting the volume. I found them a bit small and hard to use with my nubby fingers so I added my own using arcade buttons. Plus my pHat beat isn’t easily accessible. Its buried away inside the woofer box of a set of PC speakers where the amplifier died. The VU meter is viewable through the speaker cloth.