Also, regarding the power argument – USB power can be a source of noise leaking into what you hear.
USB power can be incredibly, mind-bogglingly dirty. I couldn’t believe it the first time I watched some video of some guy with an oscilloscope showing it. I guess it makes sense – I mean, keeps USB controllers and hub prices cheap – but there’s all kinds of electrical devices that have to deal with it. Anyway, point is, it’s the responsibility of the USB device containing the DAC to have a power supply that cleans that up sufficiently before feeding the DAC. It turns out that…they don’t necessarily do that. I have one USB-powered (not using a USB audio interface, or this wouldn’t be an option) mixer with 1/4" TRS output where using the USB power bus off my computer for power resulted in perceptible audio artifacts, humming and such.
This appears to be something of a not-uncommon problem, as I see various references to it online for other devices:
Some of you guys may be aware of my posts and other’s in the Topping D10 review thread. It seems that this DAC, like many audio devices that get their [power from the USB Bus, suffer from some noise coming from the USB port itself.
From my own experience, plugging the DAC into a Raspberry Pi 3B (+5v PSU and Ethernet connected) dropped the noise considerably compared to any port on the PC.
And if I can hear it, then I guarantee that there are USB audio devices that are inserting all kinds of garbage into the signal going out the output that are maybe less-egregious.
I wound up avoiding the problem with my mixer (well, at least to the point where I couldn’t hear it) by sticking the mixer onto an isolated USB charger, not on my PC’s USB tree. Now, yes, you can make a fancy power supply that avoids that, and it’s fair to say that the guys that engineered the mixer should have used a better power supply if they were gonna use USB power. But if you’ve got some guys engineering headphones and are under pressure to try to make the things as cheap as possible, because headphones are a disposable item, not to mention as light as possible because they’re gonna sit on your head, I’m not sure I’d bet on how much expense and weight they’re gonna put into the power supply feeding the DAC.
I haven’t tried quantifying how the power supplies on various USB DACs perform, though I would suggest that in a world where people are using USB audio rather than 1/8" TRS, given that you have headphone reviewers that cover things like frequency response, it’d be interesting to have a device that intentionally screws with the USB input power voltage and then have an oscilloscope or something attached to the leads coming off the magnet driving the speaker’s membrane and see just exactly how much glop from USB power is leaking through to the membrane at various dick-with-the-voltage patterns.
Also, regarding the power argument – USB power can be a source of noise leaking into what you hear.
USB power can be incredibly, mind-bogglingly dirty. I couldn’t believe it the first time I watched some video of some guy with an oscilloscope showing it. I guess it makes sense – I mean, keeps USB controllers and hub prices cheap – but there’s all kinds of electrical devices that have to deal with it. Anyway, point is, it’s the responsibility of the USB device containing the DAC to have a power supply that cleans that up sufficiently before feeding the DAC. It turns out that…they don’t necessarily do that. I have one USB-powered (not using a USB audio interface, or this wouldn’t be an option) mixer with 1/4" TRS output where using the USB power bus off my computer for power resulted in perceptible audio artifacts, humming and such.
This appears to be something of a not-uncommon problem, as I see various references to it online for other devices:
https://www.audiosciencereview.com/forum/index.php?threads/cleaning-usb-for-bus-powered-audio-devices-discuss.5899/
And if I can hear it, then I guarantee that there are USB audio devices that are inserting all kinds of garbage into the signal going out the output that are maybe less-egregious.
I wound up avoiding the problem with my mixer (well, at least to the point where I couldn’t hear it) by sticking the mixer onto an isolated USB charger, not on my PC’s USB tree. Now, yes, you can make a fancy power supply that avoids that, and it’s fair to say that the guys that engineered the mixer should have used a better power supply if they were gonna use USB power. But if you’ve got some guys engineering headphones and are under pressure to try to make the things as cheap as possible, because headphones are a disposable item, not to mention as light as possible because they’re gonna sit on your head, I’m not sure I’d bet on how much expense and weight they’re gonna put into the power supply feeding the DAC.
I haven’t tried quantifying how the power supplies on various USB DACs perform, though I would suggest that in a world where people are using USB audio rather than 1/8" TRS, given that you have headphone reviewers that cover things like frequency response, it’d be interesting to have a device that intentionally screws with the USB input power voltage and then have an oscilloscope or something attached to the leads coming off the magnet driving the speaker’s membrane and see just exactly how much glop from USB power is leaking through to the membrane at various dick-with-the-voltage patterns.