[Davesrose]

Remember, a DAC has an analog section. That's what it's doing after all: it doesn't stay digital forever. That analog stage is prone to EMI, especially if you have a poorly-grounded or poorly-isolated design.

That being said, you're not exactly on the money with USB and EMI. USB is prone to EMI: that's why there's shielding and TPs all over the place. However, these manifest as errors, not less soundstage.

Would be nice to have someone from Schiit explain their line of reasoning, but I don't think this forum section is quite ready for that.

And a DAC's analog stage is separate from the digital interconnect. When it comes to EMI: as long as a cable meets the specifications for USB (which includes shielding), it is well below the threshold for picking up EMI. Apparently, some of the cheapest USB cables can lack shielding, but even they have just a few spikes going above QP limit. That means any USB 2 interface is more than adequate for digital stereo, and a really cheap cable may get some interference (but I suspect still not audible for these applications, which are not reaching the data limits).

Another factor is how much interference is environmental. I live in an urban area and am close to a radio tower. I have collected all sorts of digital cables over the years (varying quality of toslink, coaxial, usb). I've never noticed any difference in speed or audio performance. Same is also true when it comes to guage of speaker wire with my amp and speakers. I do get interference in amp stages, though. I get hums or pick up the radio tower, so I have power strips with RF filters and a loop isolator for my subwoofer.

 

[bigshot]

Yeah, I would think if you were going to pick up interference it would be amps and speakers, not DACs and headphones. But that has been dealt with pretty well for years and years, and modern building codes have gone a long way to fixing ground loop problems. I remember back in the 70s before directional and grounded plugs being told to reverse the power plugs one at a time to find a combination that didn't cause a ground loop.

 

[Davesrose]

Yeah, I would think if you were going to pick up interference it would be amps and speakers, not DACs and headphones. But that has been dealt with pretty well for years and years, and modern building codes have gone a long way to fixing ground loop problems. I remember back in the 70s before directional and grounded plugs being told to reverse the power plugs one at a time to find a combination that didn't cause a ground loop.

Well I've found a headphone amp may pick up interference as well. Maybe not too surprising as tolerance for a speaker isn't as great a swing as headphone amp or phono stage amp (a speaker can have noise when you walk up to it, but quickly diminishes when you step back). I have (a now older) Single Power headphone amp that will pickup the radio tower. I've tried placing a cage around it, wraping circuits in foil, but did read somewhere that its tubes are notorious for picking up interference. Basically, I'll only use it for an offsite office amp now. The other issue I had was my turn table. With my previous setups, I had to have a turn table pre-amp. Even plugged into a power strip with RF, they would have hum and pick up the radio station. I then got my higher end Atmos/DTS:X/Auro receiver that has a phono input. Plugging my TT in it and grounding with it, I hear no noise (not even going up to the speaker)

 

[bigshot]

No problems here since the early 80s.

 

[Davesrose]

No problems here since the early 80s.

Haha...I can't believe you've been as close to a radio tower as I. It has driven me crazy for quite a few times with amp stages (and with my subwoofer, it took awhile for me to finally eliminate its hum with an isolator). I view my scenario as the most extreme...my problems were audibly apparent (picking up the radio station, noise, or hum). Those factors are always ground and amp characteristics it seems.

 

[bigshot]

I had a friend who lived a block from an AM station. He had a little problem at first, but with a little trial and error over the course of an afternoon I was able to fix it for him. I don't know what I did, but I fixed it. That kind of thing is a bugaboo. I remember when I worked in a film sound house and we got a ground loop hum. The head engineer pulled up the floor and sweat blood for a week before he tracked it down. You never know with something like that. But it's not really the fault of the equipment. I don't think you can design to prevent it. You can only deal with it when it crops up.

Back in the 70s, my dad was a ham radio operator. I had to quickly shut everything off when he broadcast or the speakers would blow. He instructed the whole family that if a neighbor asked if we got bad TV reception we were to lie!

 

[Davesrose]

And these things are isolated. The subwoofer I have is a DIY, and I didn't have any issues with it when I had the original 500W plate amp. It was then exhibiting issues, and I replaced it with a different amp: which initially had hum no matter what cable(s) plugged into any inputs. Getting an isolator solved its problem.

I wonder if there's anyone now who's into ham radio now? I had an uncle who had his own tower and was really into it well up to the 2000s (and then had to buy all sorts of isolators for all his neighbor's phones). Funny I'm now catching episodes of Halt and Catch Fire. Just saw an episode of a character getting back to his old ham radio, while others point out "why do that, when we have bulletin boards [now internet]"

 

[bigshot]

Ham radio operators operate repeaters to maintain a communication system for emergencies. In a big earthquake my phone wouldn't do long distance. But my dad had a local ham call me and make sure I was OK. Most of the time they just shoot the breeze and talk about their rigs and the weather though.

 

[Davesrose]

Ham radio operators operate repeaters to maintain a communication system for emergencies. In a big earthquake my phone wouldn't do long distance. But my dad had a local ham call me and make sure I was OK. Most of the time they just shoot the breeze and talk about their rigs and the weather though.

That's the impression I got from my uncle: the reason why he went through the hassle to build a big tower (that peeved all his neighbors) was that he could reach out to far distant lands for shooting the breeze. Still wonder if ham has relevance in this time.

 

[dazzerfong]

And a DAC's analog stage is separate from the digital interconnect. When it comes to EMI: as long as a cable meets the specifications for USB (which includes shielding), it is well below the threshold for picking up EMI. Apparently, some of the cheapest USB cables can lack shielding, but even they have just a few spikes going above QP limit. That means any USB 2 interface is more than adequate for digital stereo, and a really cheap cable may get some interference (but I suspect still not audible for these applications, which are not reaching the data limits).

Another factor is how much interference is environmental. I live in an urban area and am close to a radio tower. I have collected all sorts of digital cables over the years (varying quality of toslink, coaxial, usb). I've never noticed any difference in speed or audio performance. Same is also true when it comes to guage of speaker wire with my amp and speakers. I do get interference in amp stages, though. I get hums or pick up the radio tower, so I have power strips with RF filters and a loop isolator for my subwoofer.

I'm not even talking about the cable acting as an antenna itself, as after all you said yourself the cable usually includes shielding anyway. I'm saying that the analog section is prone to external factors, and that the USB digital stage, if poorly designed, can emit EMI.

 

[Davesrose]

I'm not even talking about the cable acting as an antenna itself, as after all you said yourself the cable usually includes shielding anyway. I'm saying that the analog section is prone to external factors, and that the USB digital stage, if poorly designed, can emit EMI.

Can you cite an actual USB-2 (or such) interface device that has such a poor design? I'm really wondering, because no recent device I have has any perceptual difference in audio. I do have a still (considered) high end Benchmark DAC USB that sounds great: I have a cheap DAP FIIO M7 that sounds great with USB-C to other USB cable. I also still have an old USB to coaxial adaptor (IE sound card in the box itself) and it sounds great. I got it years ago, and then it was a Chinese design. Considering that it's a USB device that seems well enough designed....just how poorly a design do we have to go that can actually have bad audio (I'm gathering even EMI may not be the main factor)?

*edit: when it comes to power charger: well yeah....not having consistent power will be a big factor for having noticeable drop outs. My A/V system is plugged into a power conditioner. During certain times, we have power drop outs. Many times, it's a hiccup where audio just has one slight delay or my OLED TV blanks out for a split second.

 

[old tech]

I had a friend who lived a block from an AM station. He had a little problem at first, but with a little trial and error over the course of an afternoon I was able to fix it for him. I don't know what I did, but I fixed it. That kind of thing is a bugaboo.

I had a ground loop hum issue with my sub. I tore my hair out for weeks trying to find the source or a remedy. Then one day it just resolved itself and never returned.

 

[bigshot]

I can see how it would be possible, but I've never found any USB interface that didn't perform flawlessly.

 

[dazzerfong]

Can you cite an actual USB-2 (or such) interface device that has such a poor design? I'm really wondering, because no recent device I have has any perceptual difference in audio. I do have a still (considered) high end Benchmark DAC USB that sounds great: I have a cheap DAP FIIO M7 that sounds great with USB-C to other USB cable. I also still have an old USB to coaxial adaptor (IE sound card in the box itself) and it sounds great. I got it years ago, and then it was a Chinese design. Considering that it's a USB device that seems well enough designed....just how poorly a design do we have to go that can actually have bad audio (I'm gathering even EMI may not be the main factor)?

*edit: when it comes to power charger: well yeah....not having consistent power will be a big factor for having noticeable drop outs. My A/V system is plugged into a power conditioner. During certain times, we have power drop outs. Many times, it's a hiccup where audio just has one slight delay or my OLED TV blanks out for a split second.

Funnily enough, the first-gen Modi. Now, I'm not talking about 'soundstage' differences in - I'm talking about buzzing and whirring from the DAC. WA7 was pretty shocking too, but it's more the entire setup which is compromised.

That being said, it's still an issue designers have to deal with. Depending on who you ask, you can say it's a trivial issue or not. I will say this, emissions testing if done properly is very hard to pass. My field is in medical devices, where the stakes are much higher regarding those. Therefore, emissions standards are much tighter in that regard and are actually a massive PITA.

Personally speaking though, DACs are generally pretty much line-wire devices to me. Amps get a lot more interesting: a lot more parameters that can potentially affect the sound.

 

[KeithPhantom]

Amps get a lot more interesting: a lot more parameters that can potentially affect the sound.

Even for these, they have to be pretty much fundamentally broken to be distinguishable in a blind test. I am talking about SINADs of 50 dB or even lower, and that's depending on the power they are providing and the level you are listening to music because distortion detection is affected by the volume you listen.