i tried on another pc and it work perfectly
on my pc (z170 pro gaming) i saw that only on 3.1 usb it seem to work, but everytime i restart the pc it don't see it, i must do a off/on on the dac for make it work
also seem that the audio sometimes disappear with this usb 3.1 connection
i don't understand why on usb 2.0 and 3.0 it work only the headphones, and if i attach the rca the nfb disappear
it's a real mistery!!
also another thing.. is normal that the nfb get very hot? over 30-35 C?
there isn't a automatically shutdown or idle? is safe make it on for all the day?
and another: why at every restart of the pc, the pc don't see the nfb until i restart it with an off/on?
and: is normal that with amanero drivers installed i have the annoying safe remove hardware icon? what mean this?
it's possible that the power supply of the speaker amplifier (24v 5A) make a incompatibility with nfb 11.28? the fact is that if remove from wall outlet the smsl power supply, the dac is fine on windows 10 (rca cables are connected)
if i push the smsl power supply on the wall outlet the dac disappear (even if the smsl if off)
Try using a USB HUB on the USB-C 3.1 port of your computer.
As I said, it is very likely that the amplifier noise is getting into USB interface. The amp's power supply, if it is a switched mode one, may generate noise and may cause inference. You said that, with the RCA cables connected to the amp, the issue happens when you connect its power supply to the outlet. This may indicate that the power supply is inducing noise, because de problem happens even if the amp is off. This amp requires a high current power supply. Try using a different power supply (at least 12V/3.5A). Cheap switched mode power supplies may have poor EMI filtering. Look for a good power supply. A simple wall wart may not be good enough. If you get a linear (not switched mode) power supply, it is better. You can also try using a 12V battery.
Be careful to no invert the voltage polarity (check the indications on amp's power input label). If you connect a battery to your amp with the inverted polarity, you will burn it.
Did you try to use a different power strip for the amp?
Did you try to lift the ground (earth) wire of one of the power strips (either the one for the computer or for the amp)?
When you connect the RCA cable, a ground loop may be formed. Lifting the ground wire from one of the devices may interrupt the noise path through the ground.
You can experiment combinations of power connections of PC, DAC and amp. You can try connect the PC in the same power strip of the DAC and the amp in another one, or connect the DAC and the amp in the same strip but the PC in the other.
Did you try to use other USB cable? The DAC does not require power from the USB, so the power pins of the USB connectors can be covered with tape.
The DAC gets a little hot, but not too much. It uses linear voltage regulators and a highly biased headphone amplifier (almost class A). These circuits generate heat.
There is no auto shutdown on idle. It is safe to leave it powered on all the time, but the only advantage to do so is keeping it warm and ready for use at its best, but this will waste a lot of energy and reduce the life time of the components, I believe.
It is normal to have the Combo384 safe remove icon in the system tray. No need to safe remove before disconnecting or powering down the unit.
I do not have the issue with having to cycle power the DAC to make the PC detecting it after reboot. I do not know what is causing this with your PC. Does this only happen with the amp connected or does it always happen? Was this happening with other PC that you said that was working?