It has the Pi2AES HAT on it, because previously, I was using AES or S/PDIF out, depending on the DAC in the system. That’s not being used at all now, since the Mystique Y is USB-only.
I am currently using one of the two blue USB 3 ports, because on RPi4s, those are not controlled by the same chip controlling the network adapters, which should mean there is much less noise/interference on the port.
I have an AudioQuest Jitterbug FMJ plugged into the other blue USB port. It’s either doing nothing, or can’t do enough to remove all the noise on the circuit.
Okay, and you only connected the Dac to the Pi, right?
If you have the opportunity, try moving the Pi a bit where you think it will be better.
Maybe try the power connection in another socket where the power strip is not, if you don’t have a PSU.
With the hope that it gets better.
Otherwise, as others have mentioned, check the wiring.
I don’t see anything on Ian’s site that offers anything like PLL controlled usb output, or any kind of jitter clock.
All the PCB Hat’s are all geared towards I2S,Coax,Aes or other.
Maybe @Polygonhell has an idea what you could try.
If the IPurifier is making a difference, it’ll likely be noise from the Pi’s power supply.
I’ve personally never had this issue using any Pi, including those with Pi2AES hats on using USB.
Cabling and placement issues are still worth investigating, I spent days trying to track down an issue I was convinced was computer USB noise and it turned out to be the placement of the DAC relative to the amp. For example if the power cable for the Pi is picking something up it’ll make it all the way through to the USB out and the IfI would likely filter it.
On the sound of the USB IPurifiers, I have one in my secondary system, and prefer it in the loop. The effect is REALLY subtle if the signal is already “clean”.
I honestly wouldn’t over think it, do what works, and at some point in the future consider getting a better streamer, it’ll be a step up, but you have to decide how much you really care when you get into multi thousand dollar streamers.
It’s not the power supply, I’m using an iFi Elite PSU for it.
The noise comes from USB. It only comes from USB. It only occurs when a USB DAC is being used. It does not occur when non-USB connections are used with non-USB DACs. It has never happened in 4 years of having this system until I used USB with this DAC.
It happened when using USB on three different MDHT DACs as well years back.
But it’s obviously not USB, there’s no possible way it could be. And I’ll take the complete lack of a response to the question about whether there is an additional HAT required for purified USB output with the Shield Pi to be “No” and that the Shield Pi won’t do anything at all regardless.
I’m so deeply sorry to have brought any of this up and to have asked the impossible once again.
It’s not the impossible, you’ve just got to put in some work to figure it out.
If the noise is present in the USB then it’s being introduced externally via one of the cables feeding the Pi. If you’ve got an IFI Power Elite, then I agree you’re good there.
Look at ever other cables and then look at the Pi itself. It will cost you 20 bucks to buy a used Pi and throw it in to see.
In the past I’ve had the very noise you describe when not playing music and it was being picked up by my Ethernet cable because it was routed next tot he mouse cable and introducing it into the Pi.
Do the work.
The Ian Canada shield is used to further clean the power coming into the Pi and shields the Pi from RFI and EMI. It works very well at that.
I would check the software settings for your Rpi4, depending on the program flashed there could be something funky with the USB output. You may also try to flash another software available for your needs.
If the USB noise has always been present even prior to this, it could be a bad Pi or bad software code. I run two Rpi4, one with the Pi2AES shield and one without and never came across any noise with or without music playing.