Switching USB cables to dac with computer running

[highstream]

(I posted a version of this on the end of a USB card thread under Music Servers yesterday, but perhaps it's more appropriate here on its own.)

 

I'm curious about a situation that in one form or another most of us have likely encountered. Let's say you're switching dacs or USB cables, but have't shut down the computer (which would in principle be the safest way) or disconnected the USB cable from the computer's or audio card's port. Or you've connected the swapped USB cable to the computer side first. That means the power line is active (5v?) when plugged into the dac, even though nothing is playing. To what degree or in what conditions is such a swap apt to cause momentary or bigger problems for a dac (functional, voltage, etc.)?

[wwaldmanfan]

(I posted a version of this on the end of a USB card thread under Music Servers yesterday, but perhaps it's more appropriate here on its own.)

 

I'm curious about a situation that in one form or another most of us have likely encountered. Let's say you're switching dacs or USB cables, but have't shut down the computer (which would in principle be the safest way) or disconnected the USB cable from the computer's or audio card's port. Or you've connected the swapped USB cable to the computer side first. That means the power line is active (5v?) when plugged into the dac, even though nothing is playing. To what degree or in what conditions is such a swap apt to cause momentary or bigger problems for a dac (functional, voltage, etc.)?

 

Maybe it will mess up your gear, or maybe it won't. USB cables are supposed to be hot-swappable, but why would you risk it? I shut off everything, including the mains wall switch to the wall outlet my power distribution strip is plugged into before disconnecting anything.

[highstream]

To avoid going off on a tangent, can we skip the general "why would you risk it" and "supposed to be" replies and focus on actual knowledge and experience, please. The question post is about possible effects on dacs. Thanks,

[wwaldmanfan]

To avoid going off on a tangent, can we skip the general "why would you risk it" and "supposed to be" replies and focus on actual knowledge and experience, please. The question post is about possible effects on dacs. Thanks,

 

I believe I answered your question without going off on a "tangent". It might damage your equipment, or it might not. Do you really expect to hear anecdotal evidence from folks here who will admit to having shorted out their expensive gear because they didn't bother to shut off the power first?

 

Or, go ahead and do it, it'll be fine!

 

I apologize if I wasted anyone's time with my response to a foolish question. Why don't you try it a few times, and you tell us what happens?

[highstream]

Do you really expect to hear anecdotal evidence from folks here who will admit to having shorted out their expensive gear because they didn't bother to shut off the power first?

I hope so, along with those having theoretical and professional experience. We've all done things were risky or seemed ok but had unintended consequences. I think it's actually a good question that's rarely discussed.

[wwaldmanfan]

I hope so, along with those having theoretical and professional experience. We've all done things were risky or seemed ok but had unintended consequences. I think it's actually a good question that's rarely discussed.

 

Theoretically, it should be OK. Not sure what makes someone who plugs a computer into a DAC a "professional".

 

Yes, we've all done things we've regretted. That actually might be a more interesting subject for a thread, although OT.

What were some of the stupidest things you've ever done? I'll start it off:

 

1) I took a joyride in an antique biplane at an airshow once, without asking the pilot if there was gas in the tank. The plane crashed. I lived. I tend to think that he was even dumber than me.

2) I turned down a chance to see Cream play at my local high school gym in 1967 (for $3) because I wasn't smart enough to know who they were.

3) I sold my Ventures Model Mosrite guitar to a pawnshop for $85 in college, an instrument that is easily worth five figures today (at least in Japan).

-OTOH-

I have never blown up my audio system because I shorted wires without shutting down the power first.

[Audio_ELF]

I'm sure at some point a DAC had died due to unplugging while powered on. On the other hand 100s of thousands of disconnects have happened without problems.

 

I've never had a problem.

 

Eloise

[One and a half]

If the media player is on and you disconnect the DAC, then the media player needs a total restart. jriver does not accept this situation very well at all.

 

If you unplug with no media player active then there is no problem electrically after all it is USB. The Os will detect a different situation and behave the way it was designed.

 

In a rare occurrence, an excess voltage on the collar of the USB will cause drama, however will only be under fault conditions.

[highstream]

In a rare occurrence, an excess voltage on the collar of the USB will cause drama, however will only be under fault conditions.

Thanks. Would you explain that last comment. The assumption here is the media player is not playing. I've had USB powered dacs where if it came unplugged, the driver often needed to be reinstalled. And I've seen USB powered dacs where there have been voltage issues plugging (power) live. It's a lot easier with an AC powered one.

[One and a half]

Thanks. Would you explain that last comment. The assumption here is the media player is not playing. I've had USB powered dacs where if it came unplugged, the driver often needed to be reinstalled. And I've seen USB powered dacs where there have been voltage issues plugging (power) live. It's a lot easier with an AC powered one.

 

Driver installs - that depends totally on the driver, some are good, some are sh$t. Also depends on the OS how forgiving it is at unplugging a USB.

 

Here's a tip for fault. Have the powered from the USB DAC or powered DAC on. With headphones on and amp say 9 o'clock, just gently connect the collar of the USB connector to the computer's shell of the USB port. There should be no noise, this is good. If there is noise, like a crackle, this means that there's a voltage between the DAC and the computer at the shell. I have seen laptop two prong supplies reach 0.5 pu mains voltage at the USB shell, worst case. This voltage will produce a current of course, right to the DAC. How the DAC gets rid of the voltage/noise is another matter, some DACs filter it out and ignore it, others just pass it on to the amp.

Interconnections are where the problems begin, the joining of two different systems with wildy varying potentials (=Voltage) on the shields.