USB disconnect sound and brief USB freezes whenever AVR switches on/off on Eaton UPS 5E 1600 G2 UPS

Whenever there's a noticeable voltage fluctuation ( typically when my air conditioner starts, wakes from standby, or when several neighbors' AC units switch on ) the UPS makes its normal relay "click" as it enters or leaves AVR.

At the exact moment that relay clicks:

• Windows plays the USB disconnect sound.
• All USB devices briefly freeze for around a second. ( both plugged at the back or the front ).
• Everything immediately starts working again afterward.

What I've tested​

I monitored USB events with NirSoft USBLogView.

If the UPS USB cable is connected to the PC:

• USBLogView shows the UPS disconnecting and reconnecting when the relay clicks.
• The USB freeze and Windows disconnect sound still happen.

If the UPS USB cable is NOT connected:

• Windows still plays the USB disconnect sound.
• USB devices still freeze for about a second.
• USBLogView shows no USB devices disconnecting or reconnecting at all.

Now normally, a two second usb freeze here and there isn't the end of the world except i do simracing and you can imagine how not being able to drive for 2 seconds here makes it completely unplayable. so i need to find a solution for this asap.

Any ideas or troubleshooting suggestions would be greatly appreciated.

I'm no expert in hardware, including power. But my reasoning says if this issue happens whether on you are connected to UPS or directly to mains and is affected by both your AC or your neighbors AC cycling on/off, the PC is seeing the voltage fluctuation and reacting accordingly. So I posed you thread to Co-pilot and low and behold my guess was partially right. Here's the answer I got:

What you’re seeing isn’t actually a USB or Windows problem. The behavior lines up with a brief power disturbance happening inside the PC whenever the UPS switches AVR modes.

A few key points from your testing make the root cause very clear:

• The USB freeze still happens even with the UPS USB cable completely unplugged.
• Windows plays the disconnect sound, but USBLogView shows no actual device disconnects.
• The freeze happens exactly when the UPS relay clicks due to voltage changes (AC units switching on/off, etc.).

That combination rules out drivers, Windows, and the UPS USB interface. What’s happening is this:

When the UPS switches AVR taps, the relay causes a very short voltage transient.​

Even though the UPS keeps the PC powered, that transient can still propagate through the PSU. Some PSUs handle these disturbances better than others. When the transient hits the PC:

• The USB host controller momentarily browns out or stalls
• All USB devices freeze for ~1 second
• Windows plays the disconnect sound because the controller hiccups
• No devices actually disconnect, so nothing shows in USBLogView

This is a known side effect of relay‑based AVR designs (like the Eaton 5E series). They physically switch taps, and that switching isn’t perfectly smooth.

In short:​

The UPS is doing its job, but the relay switching is causing a tiny power disturbance that your PSU and USB controller don’t fully ride through.

What actually fixes it​

1. Use a UPS with smoother AVR (buck/boost without relay clicking) or double‑conversion. These don’t produce the same transient when correcting voltage.
2. Upgrade to a PSU with stronger transient filtering. Some PSUs handle AVR switching without any USB impact.
3. Put the PC on a circuit not shared with large inductive loads (AC compressors, refrigerators).Reduces how often the UPS needs to switch AVR modes.
4. Optional: A line conditioner or isolation transformer can smooth out the spike before it reaches the UPS.

Bottom line
Your USB devices aren’t actually disconnecting. The PC is briefly recovering from a tiny power disturbance caused by the UPS relay switching AVR taps. Changing the UPS type or improving PSU filtering is the real solution—not drivers, not Windows settings, and not anything related to the UPS USB cable.