RPI4 with Volumio not booting as long as USB DAC is connected

I have the latest volumio version, 2.873 installed on an RPI4 with POE Hat.
There is as well a Bluetooth dongle, and CD-ROM besides the McInsoth C2500 DAC connected.
If I reboot my volumio, it won’t boot as long as my McIntosh C2500 preamp is connected. I need to turn of my preamp, after, it continous booting. It is not a power issues. I tried several RPI4 with volumio. They never boot, as long my USB DAC, provided by my McIntosh preamp is connected.
Any ideas why ? Or what I could do?
Thank you

it is indeed not a poewr issue, but a voltage issue. The USB draw to much current causing a voltage drop. If the voltage drops below 4.9VDC, the Pi won’t boot.
Please connect a volt meter and do the test. I have the same issue with a Pro-ject pre box S2 Digital. have a 25W PSU for the pi, even bought a 50W PSU, resulting in the same.
SO I bought a 5VDC relais, power by the USB port and have the Main PSU powering the DAC. No Issues anymore.

I dont understand. My McIntosh is powered. It is just the plain RPI4 what is powered. Or do I missunderstand?

I has the same symptoms when I connected a very power hungry DAC.
The fact that the McIntosh receiver is powered, does not mean that the USB recever does not draw current from the PI.

ok. thank you. understood. I will do some tests - even with different rpi4 and other than just volumio and report back. thank you