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qmacpoint
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USB Switch and device disconnection

Fri Feb 22, 2019 10:39 pm

I bought this USB Switch connect specific devices (keyboard, mouse, headphones DAC, microphone) to both my laptop and my desktop and switch between them seamlessly with the tap of a button. Seems to work fine, however I'm noticing that randomly I experience "disconnects" - for a brief period of moment I lose all input from the keyboard and mouse (for a second). Not sure how I can check what it's actually happening? Not sure if it's USB bandwidth as all of it is USB 3.0, and the keyboard, mouse, DAC and microphone are operating in USB 2.0 mode. Do you have any suggestions?

PS: Also something to have in mind is that the switch is connected directly to my desktop, it is connected to my laptop through a eGPU enclosure. BUT! I experience the same latency in my desktop. AND! I have tried two brands of USB switches already :( .
 
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Re: USB Switch and device disconnection

Sat Feb 23, 2019 10:55 am

Does the audio from the USB DAC glitch too? If not, then the problem is specific to the keyboard/mouse. Are the keyboard and mouse wired or wireless? If wireless, try putting the receiver on a USB extension cord to allow it to be placed closer to your mouse and keyboard.

It still could be a problem with the switch itself. I'll admit it is odd that you've had the same issue with two different ones, but it is possible that they use the same chip/firmware internally, since a lot of peripherals vendors just rebrand the same generic junk.
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Re: USB Switch and device disconnection

Sun Feb 24, 2019 5:59 pm

Those are very good points! Yes, both mouse and keyboard are wireless and I mounted the USB switch under my desk but directly below the keyboard and mouse, but that wasn't making interference. HOWEVER, the problem you mentioned about the switch itself being the problem did make me think: what if it's the number of USB devices connected to the switch? The USB DAC (a Corsair ST100) never glitched out (i.e. audio plays constantly, even when I get the weird latency/disconnect problems) so I decided to connect both the receivers for the mouse and keyboard to it (it has 2 USB 3.0 ports) and now I only have a microphone and the ST100 connected to the switch - and so far, no problems! I'll keep an eye on this and see if it ultimately resolves my problems. I'm thinking that these switches had controllers designed with two ports in mind, and then later just added more ports into it. I'll keep an eye on this over the week to see if it repeats again - and so I haven't had a single glitch in Overwatch, so it looks promising!
 
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Re: USB Switch and device disconnection

Sun Feb 24, 2019 6:13 pm

Assuming that this really fixed it, I'm going to speculate that moving the mouse/keyboard receivers to the extra USB ports on the DAC helped by reducing interference with the wireless signals. Maybe the DAC is less "leaky" (in EMI terms) than the hub. Given that the ST100 has an aluminum casing, and DAC designers need to pay attention to EMI issues if they want to get clean analog audio, this is entirely plausible.

One potential downside is that this might actually degrade the signal-to-noise ratio of your DAC slightly. But if the fidelity if the DAC still seems acceptable, I'd say you're golden.

FWIW I've found that the best way to minimize glitches with wireless keyboards/mice is to use passive USB extension cables, to get the receiver(s) a foot or more away from anything containing active electronics. The signals from wireless keyboards/mice are pretty weak in order to maximize battery life and prevent them from interfering with other nearby wireless devices; they are easily overwhelmed by any EMI sources close to the receiver.

In fact, I just had a similar issue recently. I had rearranged my desk, and my mouse was occasionally glitching. The mouse receiver was on an extension cable, but the rearrangement had placed it right behind my monitor. The monitor was either blocking or interfering with the mouse signal. Moved the mouse receiver so that it is under the monitor instead of behind it, and the problem went away.
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Re: USB Switch and device disconnection

Sun Feb 24, 2019 7:00 pm

That's also plausible, the actual receivers are now 1 feet away from the keyboard and mouse, so perhaps that also cleared the interference. What was interesting was the fact that both mouse and keyboard glitched out at the same time, which led me to believe that it could've been purely switch-based problems. I guess anything goes - there are so many pieces at this point in time heh!
 
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Re: USB Switch and device disconnection

Sun Feb 24, 2019 7:25 pm

Yeah, impossible to say. Maybe it was right on the edge, and some other interference source was kicking in occasionally (e.g. your cell phone pinging the tower? someone nearby using a microwave?) that pushed it over the edge.

Wireless tech these days is akin to voodoo and black magic. The fact that the clock speeds of common system components (CPUs, DRAM, PCIe, USB3, ...) are in the same frequency bands as the radio frequencies used by a lot of wireless tech doesn't help either. Makes cross-interference a lot more likely if someone cuts corners on EMI suppression. Leakage from microwave ovens is right smack in the middle of that range too. Fun times.
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Re: USB Switch and device disconnection

Sun Feb 24, 2019 9:29 pm

Could've been my phone! was sitting on top of the desk (in a cradle/dock) in the same area as the USB switch! That could've done some things for sure!
 
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Re: USB Switch and device disconnection

Wed Mar 13, 2019 5:10 pm

This started happening again, and did more digging - it seems that USB input devices may cause too much EMI that will actually disrupt the USB transmission over TB3... who knew!!!
So in summary: It was EMI interference, but from the very same devices I was trying to use!

If anyone has a Mantiz Venus and has the same problem, the links for fixing this are here: https://mymantiz.com/pages/faq

PD: The process to update the firmware is super janky.

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