Hello
 
My USB DAC (Acoustic Research UA1), requires me to plug/unplug USB port manually each time after a full power on/off cycle..
 
I don't need to do this for reboots or sleep on/off, but whenever i completely turn off the laptop, on the next power-on, i'll need to do this manual plug/unplug to get it recognized by my laptop
 
During the power-off, the USB still shows the light that its connected (i presume similar to the fact that the laptop is able to charge phones while being off), but during the boot sequence the power goes off and it never comes back until i manually perfomrm the cable plug/unplug
 
Do you have any idea how i could fix it ? I've tried every possible setting change on USB power management, as i don't have this issue on my desktop PC
 
Thx

The obvious question is whether you did an OS update at around the time that this happened. What OS are you using? Did you have to load specific drivers for your DAC, or did your OS see it immediately?
 
There was one occasion recently when Broadcom asked Microsoft to push out a driver change, deliberately so that clones of Broadcom's chips (that some manufacturers were using) would stop working.

check USB/power options in BIOS at bootup ?
might be a Wake on such and such option there

Hi, i looked at the USB power as well as BIOS options. It's a XMOS type DAC so i have installed its dedicated driver to make it work. The OS is windows 10, but this device works well on my desktop PC.

If the equipment is working on another machine, and not this one.... but it did work a while ago and suddenly stopped ... then that points to the operating system and the drivers for the USB bus.
 
I presume your desktop PC is a different OS?

I googled this and saw a few other posts about similar problem. I didn't see an easy fix though. 
 
If u haven't messed with USB hub root Power option in Device manager, maybe that
http://helpdeskgeek.com/windows-xp-tips/prevent-windows-from-powering-off-usb-device/

my desktop is the same OS. Its a new purchase. I didn't have this issue with my old DAC, so its puzzling.

Laptops tend to supply reduced power to USB, which isn't great with certain USB DAC interfaces that might expect the full 0.5A on USB 2.0 (0.9A on USB 3) that a desktop PC would provide. 
 
On the other hand, it really sounds like a dodgy USB port to me. I find that connecting via any old USB hub tends to help with USB DAC issues. You could try a powered USB hub too.

Thx, i tried it with all three USB port. I'll try to test it on my 2nd laptop during the weekend. What puzzles me is that, once i plug in/out the USB, it gets well recognized and works without any issue... its just the initial recognition that's not happening automatically -(