Popping in speakers when starting Wiim Ultra

[chito.limson]

Here’s my setup:

The Wiim Ultra is connected to the Fosi Audio ZD3 preamp/DAC via USB. Trigger out from Wiim to ZD3.

The ZD3 is connected to two Fosi Audio V3 Mono via XLR.

In the ZD3, volume control is BYPASSED. I control volume using the Wiim Ultra on the app or on its remote control.

When I turn on the Wiim Ultra, everything else turns on too as they should. However, two pops come out of the speakers: one soft and one louder than the first pop. Even if I start the Ultra with the volume set at ZERO, the pops still happen. I removed the trigger cable between the Ultra and the ZD3, and turned on the ZD3 a little later after starting the Ultra, but the pops still happen.

To experiment, I removed the USB connection between the Ultra and the ZD3, and switched to coaxial connection between the two. I put back the trigger cable between the two units and the start up pops disappeared.

Why is this happening?

 

[harkpabst]

I removed the trigger cable between the Ultra and the ZD3, and turned on the ZD3 a little later after starting the Ultra, but the pops still happen.

Are you saying that the pops happen as soon as the WiiM Ultra awakes from standby, even if the ZD3 is still "off"?

 

[chito.limson]

Are you saying that the pops happen as soon as the WiiM Ultra awakes from standby, even if the ZD3 is still "off"?

When the trigger cable is still attached, both the Ultra and the ZD3 turn on almost at the same time. I removed the trigger so only the Wiim would turn on first, and then I turn on the ZD3 separately after a little delay. When I do this, the pops still happen.

 

[harkpabst]

When the trigger cable is still attached, both the Ultra and the ZD3 turn on almost at the same time. I removed the trigger so only the Wiim would turn on first, and then I turn on the ZD3 separately after a little delay. When I do this, the pops still happen.

Do the pops appear when waking up the WiiM Ultra or when waking up the ZD3 then?

 

[chito.limson]

Do the pops appear when waking up the WiiM Ultra or when waking up the ZD3 then?

When waking up the ZD3.

This happened when the Ultra and the ZD3 were connected via USB.

When I connected them via coaxial, the popping doesn’t happen.