BBurns Loc: South Bay, California

Gene is correct.

TheShoe Loc: Lacey, WA

Unfortunately, coax is not an option. USB is the only choice and I did use a new cable early in my efforts.

TheShoe Loc: Lacey, WA

All devices are plugged in to the same UPS. Does that count? I live in a retirement community, so I have no ability to mess with the house wiring.

BBurns Loc: South Bay, California

If that is the case I would first make sure that you have a good ground connection through the strip. Then verify that all of your gear is polarized correctly. Any one device plugged in backwards can reek havoc with the kind of problem you describe.

If any of our other guys have ideas, Gene Chris, please chime in.

TheShoe Loc: Lacey, WA

What strip, it is a UPS. There is only one way to plug a 3-prong plug into a receptacle.

BBurns Loc: South Bay, California

Let's clarify some things.
Are we to understand that your UPS has enough receptacles to accommodate all of your devices?
You are not using an additional plug strip coming out of the UPS.?
Are we to understand that all of your devices have 3-prong plugs?
A simple device such as a Receptacle Tester will verify this for you.
Test the receptacle the UPS is plugged into first.

Hypothetically, are we to presume that your UPS has not been previously compromised by a power surge?

TheShoe Loc: Lacey, WA

I have thought of the peripherals as victims rather than culprits from the very beginning.

burkphoto Loc: High Point, NC

1) A UPS sold for home use is just a surge protector power strip until the AC line power goes out. Then the battery takes over. At that point, a few of its outlets remain powered up by an inverter and battery circuit, giving you a few moments to shut things down (if the battery hasn't died of age and neglect).

2) While it is possible for an outlet to be wired backwards, it is unlikely. Still, a cheap outlet tester is worth using.

3) I still don't think your issue is power source related. I think it is circuit design related. Most computers are cheaply built and not designed with audio in mind. It's most likely that the sudden rush of power at startup is the culprit here, and avoiding the effects of it is a prudent approach.

Leave the amp volume all the way down when you turn off the system. Start the system and THEN turn on the amplifier and you should avoid the snap, crackle, and POP noises. (In my experience, it's usually a low frequency 'whump'.) I've done that since the early 1970s to protect my speakers. Volume down, then power off. Power on, wait for the speaker relays to click, then volume up. No use ruining good speakers and waking the dead!

TheShoe Loc: Lacey, WA

I have used an outlet tester which indicated that the wiring was correct. I never hinted that it was power source related. I agree that it is circuit design. The m/b maker will not own the problem, neither will AudioEngine, the maker of the DAC and the powered speakers. That leaves me with the necessity of circumventing it.

I now have a USB hub with switches on the ports. I turn the switch off at shutdown and sleep times. I have disabled the system from going to sleep on its own; a sleep command is required. I also do not allow anything except for keyboard input to wake it up.

Thanks to all for the analyses and suggestions.

BBurns Loc: South Bay, California

My approach was to make sure & eliminate the power source as a possibility.
Ground on a M/B may not be the same as chassis/earth ground. Signal(audio) ground & digital ground are not necessarily the same. It would not surprise me in the least that you discover that the digital commons are floating on one or more devices. A few millivolts can generate a very loud noise. In some high end audio gear a clamp circuit is used to ground the input of the audio amp during input switching & power up/down modes.

Now that you have explained more, I believe you are on the right path with the USB switch. Chasing this kind of problem can be very frustrating. Good Luck

BebuLamar

I still think it's the DAC model. A good one won't have that problem.

TriX Loc: Raleigh, NC

I would be glad to be on your thread with the manufacturer of the DAC. When I answered initially, I didn’t realize you were actually seeing sparks.

Regarding grounds, the USB spec requires the metallic shell of the connector to be connected to the shield, but USB connectors on MBs and maybe the DAC, have plastic USB headers, so the shield may not actually be attached to earth ground. There is however a ground pin on the USB cable/connector, so if it’s actually attached to the chassis ground on the MB and IF the DAC analog output has one side grounded to DC ground, theoretically, the Computer and Amp May all be on the same ground, but that’s a lot of ifs. Also, the computer case ground and the amp chassis should both be on the same house safety ground via the 3 pin power plug (which may not be a good thing) assuming your house is new enough to have 3 pin AC outlets AND the ground pin is REALLY on earth ground. In the professional audio world, the first thing many sound engineers do is break off the safety ground pin of all the power cords to prevent ground loops, but in this case, I’d at least make sure the computer chassis and the amp or on the same ground just as a test. And as previously mentioned, chassis ground may not be the same as DC or signal ground.

The real question to me is whether the spark is static electricity or DC/AC voltage. Have you probed with a DVM or scope between the two conductors or from each to ground where the spark occurs to see if there is a potential difference? If there is actually measurable voltage present, my next question is how is the DAC powered, via the USB port or does it have a separate power supply?

I think in the end, Bill’s suggestion of just turning down the audio gain when starting the computer will address the issue. I use an external DAC also, but I attach it to the amps and USB port and power up the computer (an IPAD in this case), before I turn on the amps (which come up slowly because they are tube amps anyway). Then I turn up the gain when everything is up. For reference, who is the manufacturer and model number of the DAC? (And let us know if a powered USB hub addresses the issue).

Edit: I’ve been off this thread for awhile so didn’t see your comments on the UPS and having tested the AC line and ground, so ignore my comments on outlets.

Canisdirus

Could be a ground loop issue...

TheShoe Loc: Lacey, WA

I haven't done any probing with a DVM or any other instruments. Back in the 1990s, I had some pretty severe damage to my spinal cord in the upper cervical area. Since then, it would be dangerous or foolhardy for me to undertake anything that requires precise control of my hands. I am not equipped to perform electrical tests.

That said, the new USB hub is powered by its own brick. Given all that you have said, I thought the experiment of putting the machine to sleep and waking it up without switching the port off would perhaps be interesting. The result was that there was no simulated gunshot, not even a tiny burp. I tried three more times all with the same result. Shutdown/power on produced the same result. It appears as though the problem has been solved.

In answer to some of your questions, my DAC is an AudioEngine D1 and the speakers are AudioEngine A5+ which are powered speakers with the amp packed into the left enclosure.

TriX Loc: Raleigh, NC

An excellent outcome!