Constant 1kHz whine on audio with Daisy Pod

I’ve just hooked up my Daisy pod for the first time, and running through the example projects through the web programmer, I’m finding I have a really loud 1kHz tone on the audio (about 40dB above the noise floor). Looking at the waveform in a scope in my DAW, I can see it looks a 15% duty cycle square wave so I’m guessing it’s related to a poor power supply (from USB) ?

Is there anything I can do about this ? It’s pretty unusable as it is right now. Is there a way of powering the daisy pod from an external PSU? I don’t see any suitable terminals.

Try running Daisy from a rechargeable USB battery pack, such as is used for charging mobile phone.

Good idea. However, when I power the pod from a USB power pack which is fully charged, I get massively loud mains hum which gets louder when I touch the case of the USB battery pack. I do not get the same louder buzz when I touch the metal chassis of the jack plug, so can only assume it’s something about the earth connection on the pod ?

Looking at the schematics I can see the AGND and DGND are joined via the pod, so not sure where to go next.

Turned out it was a dry solder joint on gnd pin of the line out jacks. They were all a bit dry actually, but now I’ve touched them up, it’s all running much better with a hugely improved noise floor!


Actually, there is still a 1kHz tone when powered from a passive USB hub but it’s much lower in level and goes away completely when running from the battery pack or powered socket.

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Just for knowledge sake, computer USB ports are often not isolated. A computer will spill usb noise into your devices. You can even hear more noise as you move your mouse or computer does something intense.

It’s just sort of the way it is I suppose. I’ve had $2000 synths that have this issue. And $75 dev kits :slight_smile:

To stop it, you need to buy a usb isolator that goes at the end of the usb cord. It’s like a little op amp buffer on a board that decouples errant PC noise from entering your device. The issue is some computers and possibly devices are finicky with the isolation. I wonder if this is why manufacturers aren’t always isolating USB ports.

I had similar issues when working with the ESP32. It seems there are ground issues with USB ground and Audio ground. A “audio isolator” helped to solve the problem. It acts like a DI box but it is a cheaper solution with two internal audio transformer coils.
example: Ground Loop Noise Isolator Anti interference Safe Accessories Clear Sound Car Audio Aux With 3.5mmCable Home Stereo Portable|Speaker Line| - AliExpress

Just back because I have gotten a pod and have tested it. An audio isolator may help. But not always. The noise has made it to the audio path already inside the daisy. Likely due to EMI from your computers processor and chips. So it’s dirty power coming in as I understand it. Trying to push the noise to ground won’t always work because, at least in the case I mentioned, it isn’t a grounding issue. It’s an interference/isolation issue on the pc side.

Can report: no noise on usb power straight from power distribution. Yes noise coming from usb hub connected to computer. No noise from usb when using one of these usb isolators.

Also, ground loop noise from MPC usb and high frequency noise. Then using a transformer audio isolator, the ground loop goes away, but the high frequency noise is still left. Just using the usb isolator there gives me no ground loop and no noise.

Could these be more built into devices to prevent it altogether? Idk probably. They are fairly cheap at $10 each. But, for ex. my Sequential OB-6 and also like every synth I’ve owned and plugged into usb has this type of noise without the usb isolator. You can even move your mouse and stuff and the noise changes. And normally these sort of devices fix the issue. There are higher quality options as well of course.

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