[PROBLEM] More then one USB device

[Pytanie]

Not possible in moOe to live switch between 2 USB audio devices.

Whats your usage scenario for having 2 USB audio device connected at same time?

Thank you for information.

I want to drive from moOde on RPI (via USB 384, 256DSD) two devices - not simultaneously of course. 
The first is Digital Amp (PowerDAC) - without sound-deteriorating digital-to-analog conversions. The digital signal drives the speakers directly, with no translation and no middleman. Neither headphones jack, nor digital or line analog output onboard. 
The second is an analog tube headphones amplifier - through DAC with analog only output.
May be, modification of one of the configuration files could solve it (change USB device output string)?

Pytanie

Quite unusual set-up, a headphone amp driven via USB... Is there any reason for NOT running the said HP amp from the RPi's own HP OUT?

I'm not ruling out the method you have proposed.
But if no law against it I still prefere to drive my HP amp via USB and my external DAC.
I'm simply not sure if the DAC wchich is implemented into Broadcom BCM28xx SoC chip is the one I prefere.
By the way - "Quite unusual set-up..."  I understand it's a compliment