Good quality USB cable from laptop to DAC - Page 3 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 79Likes
Reply
 
Thread Tools
post #61 of 242 Old 04-26-2019, 05:55 PM
AVS Forum Special Member
 
torii's Avatar
 
Join Date: Mar 2015
Posts: 6,695
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 3322 Post(s)
Liked: 1874
Quote:
Originally Posted by alan0354 View Post
What kind of engineer was your father? EE? what area of the field?


Electronics technology is moving at light speed, before I retired, we only have USB2 which is 400MHz, now USB3.1 and 3.2 is 5GHz and 10GHz.

his last 20 yrs or so he was project engineer in making **** for anything with an engine...from trains to big rigs to ac to lawnmower to mcdonalds fryers....but I believe his initial degree was ee... he got hired to do a project and moved on...project to project...usually about 2-3 yrs.


his big breakthru with design was brockway trucks back in 70's....made his money in mechanical engineering I guess but he knows freaking everything if soeone asks...

Power: Marantz sr7008, NAD C 275Bee x 2, Video: Oppo 103, Samsung 75un6300
Speakers: Focal aria 948, Focal cc900, Klipsch synergy KSF 10.5, Magnepan LRS
Subs: Rythmik FV25HP, Rythmik FV15HP

Last edited by torii; 04-26-2019 at 05:59 PM.
torii is offline  
Sponsored Links
Advertisement
 
post #62 of 242 Old 04-26-2019, 05:59 PM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by torii View Post
his last 20 yrs or so he was project engineer in making **** for anything with an engine...from trains to big rigs to ac to lawnmower to mcdonalds fryers....but I believe his initial degree was ee... he got hired to do a project and moved on...project to project...usually about 2-3 yrs.
Ah, he's mechanical engineer even thought he's EE background. It is more common than people think, my degree was biochemistry, but never work a day in that field. Started out modifying guitar amps, got into electronics and had a full career in EE. Now going in full circle and into audio amps.


I like project that last only a year or two. Earlier in my career, I change job every 3 years max, go into different facet of EE to gain experience and learn different things.
torii likes this.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
post #63 of 242 Old 04-26-2019, 06:01 PM
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 11,749
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 4671 Post(s)
Liked: 3470
Quote:
Originally Posted by alan0354 View Post
Like I said, using ferrite is a standard way in reducing noise......reducing ground loop
Let's ask an EE, as you suggested at one point. @DonH50
Don, ferrite beads on USB cords, say between a laptop and an outboard DAC, can help reduce some forms of noise, however in the specific instance where there is a ground loop, say because the laptop's ground is plugged to a different AC plug than the DAC, the question is this: will ferrite beads (either applied aftermarket or from a prefabricated USB cable which uses them) help eliminate the ground loop problem? Thanks.

Last edited by m. zillch; 04-26-2019 at 06:12 PM.
m. zillch is offline  
Sponsored Links
Advertisement
 
post #64 of 242 Old 04-26-2019, 06:16 PM
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 11,749
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 4671 Post(s)
Liked: 3470
More proof ferrite chokes on USBs don't eliminate ground loop problems is the fact that people will dish out $50 or more on units like the USB ground isolator I linked to earlier, whereas if all they needed was ferrite beads on their USB cable they could buy them for cheap.

Last edited by m. zillch; 04-26-2019 at 06:21 PM.
m. zillch is offline  
post #65 of 242 Old 04-26-2019, 06:20 PM
AVS Forum Special Member
 
torii's Avatar
 
Join Date: Mar 2015
Posts: 6,695
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 3322 Post(s)
Liked: 1874
Quote:
Originally Posted by m. zillch View Post
More proof ferrite chokes on USBs don't eliminate ground loop problems is the fact that people will dish out $50 or more on the USB ground isolator I linked to earlier, whereas if all they needed was ferrite beads on their USB they cable they could buy them for cheap.
I obviously dont know answer...but I feel and maybe you can admit to a problem may exist...the solution is????


ofc if dont have problem with noise and laptop....

Power: Marantz sr7008, NAD C 275Bee x 2, Video: Oppo 103, Samsung 75un6300
Speakers: Focal aria 948, Focal cc900, Klipsch synergy KSF 10.5, Magnepan LRS
Subs: Rythmik FV25HP, Rythmik FV15HP
torii is offline  
post #66 of 242 Old 04-26-2019, 06:23 PM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by m. zillch View Post
Let's ask an EE @DonH50
Don, ferrite beads on USB cords, say between a laptop and an outboard DAC, can help reduce some forms of noise, however in the specific instance where there is a ground loop, say because the laptop's ground is plugged to a different AC plug than the DAC, the question is: will ferrite beads (either applied aftermarket or from a prefabricated USB cable which uses them) help eliminate the ground loop? Thanks.

Some cases it will, not 100%. It's easy to put in to try it. Cheap and dirty. I have a few of these clipped on ferrite as shown, just open it, loop 1 turn of the coax and clip it close. Just try it, only 10sec to clip on and 10sec to take it off.



It is all about ground loops, this form an inductor between the two grounds and break the loop. Ground loop is not only limit to 60Hz and 120Hz, you have high frequency loop that is even worst, not only the ground noise, the loop emits EM waves that couple to other devices through air. Breaking the loop is very important. One good example is those loop antenna on tv for UHF, it's a round loop. If you drive current through, it will emit EM wave as good as receiving UHF signal from the air to the tv. It's all about the current through the loop.


There is no one fix, just try the easiest first, if it works, great. If it doesn't, use the one you suggested the USB isolator for $49. That should work.


I know people keep putting down TOSLINK, but that is a true optical connection, there will be NO ground loop. I don't know the detail why it's not good, but in the sense of noise, that should be the best. I don't think people that invented USB have dream of using for audio that is so much more sensitive to ground noise. When we look at the noise, if it is 1% or less, it's perfect!!! But for audio, that's bad.
Attached Thumbnails
Click image for larger version

Name:	Ferrite 1.JPG
Views:	13
Size:	40.2 KB
ID:	2558630   Click image for larger version

Name:	Ferrite 2.JPG
Views:	9
Size:	30.5 KB
ID:	2558632  
torii likes this.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
post #67 of 242 Old 04-26-2019, 06:26 PM
AVS Forum Special Member
 
torii's Avatar
 
Join Date: Mar 2015
Posts: 6,695
Mentioned: 47 Post(s)
Tagged: 0 Thread(s)
Quoted: 3322 Post(s)
Liked: 1874
if any of my laptops had toslink...that would be my choice for music/audio

Power: Marantz sr7008, NAD C 275Bee x 2, Video: Oppo 103, Samsung 75un6300
Speakers: Focal aria 948, Focal cc900, Klipsch synergy KSF 10.5, Magnepan LRS
Subs: Rythmik FV25HP, Rythmik FV15HP
torii is offline  
post #68 of 242 Old 04-26-2019, 06:35 PM
AVS Forum Special Member
 
drewTT's Avatar
 
Join Date: Nov 2007
Location: Newport Beach, CA
Posts: 4,501
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 1993 Post(s)
Liked: 2150
Good time to mention the Audioquest Coffee I am about to order? lol
Scotth3886 likes this.

LG OLED65E8 | Plinius Hiato | Dynaudio Contour 20 | Dynaudio Stand 6 | REL T/9i | PS Audio DirectStream Junior | Furman IT-Reference 15i | Sony PS4 Pro | Synology DS916+ | Apple TV 4K | BDI Mirage | NEEO | Focal Shape 40 | iFi Pro iDSD | iFi Pro iRack | roon
drewTT is offline  
post #69 of 242 Old 04-26-2019, 08:06 PM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by torii View Post
if any of my laptops had toslink...that would be my choice for music/audio
You know, there's a really stupid way to avoid ground loop, use only the battery to power the laptop when listening to music, then charge it up when you are not using it for music. No plug to the wall, no ground loop, simple. That would be a good test to make sure it's ground loop. If you still have noise, then it's something else. One can never be so sure what is the noise problem. Designing fancy things is a lot easier, making sure it is stable ( no oscillation) and not noisy is where the rubber hits the road and show how much the EE has.

Noise is very tricky, I am very into fixing noise problem, it is very challenging. I was contracted to KLA Tancor to layout and fix noise problem for their special CCD camera that was 3G pixels.....that is 3000M pixels. Remember the newest camera in 2019 is like 25M pixels, this is 120 times finer.....in 2003. They actually contracted us to do the layout for them and it's all about grounding, ground loops and ground bounce. All signal integrity design. All the design is to lower noise for the image.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
post #70 of 242 Old 04-26-2019, 08:07 PM
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 11,749
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 4671 Post(s)
Liked: 3470

"A ferrite bead acting as a sheath current filter on a USB cable"

"Ferrite sheath current filters are used for noise suppression, combating noise such as radio frequency interference. They have no electrical isolation and cannot prevent ground loops."

Source: Sheath Current Filters
m. zillch is offline  
post #71 of 242 Old 04-26-2019, 08:17 PM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by m. zillch View Post

"A ferrite bead acting as a sheath current filter on a USB cable"

"Ferrite sheath current filters are used for noise suppression, combating noise such as radio frequency interference. They have no electrical isolation and cannot prevent ground loops."

Source: Sheath Current Filters



See, you are thinking of ground loop in conventional hum and buzz noise. Ground loop can extend to GHz microwave. This kind of noise from laptop is ALMOST certain is not 60Hz type of conventional noise. The noise is from the oscillation that run the CPU, the CPU read and write to memory, oscillator for the USB, also the switching power supply that power the electronics in the laptop.



Ferrite is to isolate the ground at RF frequency, it won't work at audio frequency and it does NOT isolate the ground at audio frequency(or else it would be too easy to fix all the hum and buzz noise). But everything in the laptop is run at hundreds of MHz, one loop of the ferrite will create impedance of a few ohms and is good enough to break the loop.


If you only read audio papers, their ground loop is hum and buzz, but that is only a tiny bit of the noise spectrum. Once you start talking about digital interface, you open a whole different world. And that world is actually my specialty. You can take my word, or you can actually ask those that write those paper to directly talk to me over the forum. There is a big world outside of audio electronics. RF, high speed digital links and low noise is where I worked my whole career and this USB is exactly that.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
post #72 of 242 Old 04-26-2019, 08:17 PM
AVS Forum Addicted Member
 
DonH50's Avatar
 
Join Date: Feb 2010
Location: Monument CO
Posts: 12,102
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 3141 Post(s)
Liked: 3099
Quote:
Originally Posted by m. zillch View Post
Let's ask an EE, as you suggested at one point. @DonH50
Don, ferrite beads on USB cords, say between a laptop and an outboard DAC, can help reduce some forms of noise, however in the specific instance where there is a ground loop, say because the laptop's ground is plugged to a different AC plug than the DAC, the question is this: will ferrite beads (either applied aftermarket or from a prefabricated USB cable which uses them) help eliminate the ground loop problem? Thanks.
Disclaimer: I rarely visit this sub-forum and did not read any of the previous posts.

A ferrite bead around the cable will do nothing for a conventional (audio) ground loop.

The ferrite works by damping ("absorbing") EM fields and is essentially a high-frequency (RFI) noise suppressor. It doesn't really do anything at very low frequencies. A ground loop occurs due to difference in ground potential between two potential signal paths. It is always important to remember that current is a loop, with a plus and minus ("ground") side, and will take the path of least resistance. If that path is not the desired path, e.g. is to another ground point instead of through your signal cable, then the offset will look like signal to the receiver. Another way to think about it is that the receiver amplifies the voltage difference between the (+) and (-) sides of the cable. A ground loop makes the (-) side move relative to the (+) side and so the receiver amplifies that difference. For audio, the most common ground loop is due to AC chassis current (coupled noise) at 50 or 60 Hz (depends upon where you live). That introduces a LF signal on "ground" that gets amplified to provide that annoying buzzing sound. Gain and harmonics generated in the receiver circuitry make it make audible and more "raspy".

A little more info here: https://www.audiosciencereview.com/f...52/#post-35364

There can be a lot of RFI on a USB cable, and if any of that HF gets modulated to the audio band anywhere in the receiver, then the ferrite can reduce the noise in the audio band by eliminating the root cause. But that noise is not from a ground loop though it may sound similar (or not). It is RFI the receiver could not reject; the ferrite reduces the RFI injected into the receiver and thus the noise level is reduced.

HTH - Don
m. zillch and 18Hurts like this.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

Last edited by DonH50; 04-26-2019 at 08:36 PM.
DonH50 is online now  
post #73 of 242 Old 04-26-2019, 08:18 PM
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 11,749
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 4671 Post(s)
Liked: 3470
Quote:
Originally Posted by DonH50 View Post
A ferrite bead around the cable will do nothing for a ground loop.
Thank you.

Last edited by m. zillch; 04-26-2019 at 08:22 PM.
m. zillch is offline  
post #74 of 242 Old 04-26-2019, 08:23 PM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by DonH50 View Post
A ferrite bead around the cable will do nothing for a ground loop.

The ferrite works by damping ("absorbing") EM fields and is essentially a high-frequency (RFI) noise suppressor. It doesn't really do anything at very low frequencies. A ground loop occurs due to difference in ground potential between two potential signal paths. It is always important to remember that current is a loop, with a plus and minus ("ground") side, and will take the path of least resistance. If that path is not the desired path, e.g. is to another ground point instead of through your signal cable, then the offset will look like signal to the receiver. Another way to think about it is that the receiver amplifies the voltage difference between the (+) and (-) sides of the cable. A ground loop makes the (-) side move relative to the (+) side and so the receiver amplifies that difference. For audio, the most common ground loop is due to AC chassis current (coupled noise) at 50 or 60 Hz (depends upon where you live). That introduces a LF signal on "ground" that gets amplified to provide that annoying buzzing sound. Gain and harmonics generated in the receiver circuitry make it make audible and more "raspy".

A little more info here: https://www.audiosciencereview.com/f...52/#post-35364
I take that you are EE, now we can really get deep into the details of ground loop, grounding and noise. It's very hard to explain this in non technical way.

I think I explain very clear in post #71 and the earlier. Ground loop is not limited to audio frequency, it extend to all the way to RF and microwave. It just manifest into different symptoms. Ferrite definite can break the loop at RF, which is the case where laptop induce noise to the later stage through the USB ground shield.

If you have your opinion, I would like to look at it, you can be technical here.


Quote:
Originally Posted by DonH50 View Post
There can be a lot of RFI on a USB cable, and if any of that HF gets modulated to the audio band anywhere in the receiver, then the ferrite can reduce the noise in the audio band by eliminating the root cause. But that noise is not from a ground loop though it may sound similar (or not). It is RFI the receiver could not reject; the ferrite reduces the RFI injected into the receiver and thus the noise level is reduced.

HTH - Don
The ferrite is not just to stop the RF, if that is the case, the 400MHz or faster USB signal cannot pass through. It serves as COMMON MODE CHOKE that will not affect the RF inside the cable, BUT act as an inductor in common mode.....which is opening the two grounds.


Here is the paper from Murata on differential and common mode choke.
https://www.murata.com/~/media/webre...ow/26to30.ashx


USB is differential signaling and have good common mode rejection, that's not where the noise comes from. The shield is the problem noise are most like from the shield that connect the two grounds.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.

Last edited by alan0354; 04-26-2019 at 08:49 PM.
alan0354 is offline  
post #75 of 242 Old 04-26-2019, 09:03 PM
AVS Forum Addicted Member
 
DonH50's Avatar
 
Join Date: Feb 2010
Location: Monument CO
Posts: 12,102
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 3141 Post(s)
Liked: 3099
Quote:
Originally Posted by alan0354 View Post
I take that you are EE, now we can really get deep into the details of ground loop, grounding and noise. It's very hard to explain this in non technical way.

I think I explain very clear in post #71 and the earlier. Ground loop is not limited to audio frequency, it extend to all the way to RF and microwave. It just manifest into different symptoms. Ferrite definite can break the loop at RF, which is the case where laptop induce noise to the later stage through the USB ground shield.


If you have your opinion, I would like to look at it, you can be technical here.

I did not read your post, sorry. Long day. I just responded to @m. zillch .

<pause to read>

I can understand your viewpoint (yes, I have an EE degree; my current day job involves GHz interfaces, and most of my career focused on various data converter and RF circuits from hundreds of MHz to a few hundred GHz). I think we said pretty much the same thing but differ in how broadly we define "ground loop". While anything from DC to light modulating the ground could be properly considered a ground loop, for audio circuits by convention if not by standard (AES) it is limited to the 50/60 Hz current from the incoming (AC) power supply. The RF ground noise, while also a ground loop issue, is deemed RFI in the audio world and considered a separate noise component, at least IME. To an EE that is a distinction without a difference, but to an audio guy (who probably has limited RF experience) it is a big difference. Debugging and fixing a LF ground loop caused by coupled (E or M) field from the AC line is a different thing than dealing with RFI.

This is one of those things that is always gnarly. Technically the datastream on a digital link creates (injects) noise that couples into the receiver. That can occur on the signal (plus, hot) or return (ground) path. I tend to think of RFI as more a noise injector or aggressor rather than a (LF AC) ground loop that follows a much longer path and occurs at a much lower frequency. Thus I treat them differently (repeating above, sorry, end of a 60+ hour work week and as a reward get to work tomorrow (Saturday) since one of my tests is flaking out).

It is probably worth noting that differential (balanced) audio circuits do a pretty good job at handling ground loops (the LF AC type) by facilitating ground isolation since the AC shield is not (or should not be) the AC signal ground. But common-mode rejection falls off rapidly with frequency so even common-mode RF noise will generally be a problem to a differential circuit. We depend upon the isolated shield to "block" RFI from reaching the inner signal pair.

Bottom line is I do not disagree with your broader definition but in practice, at least that I have had in and out of audio, the two are treated differently in the audio world (by audiophiles and design engineers). I had the same problem when I first read about "passive bi-amping" in the context of AVRs: to me, passive bi-amping means a passive (RLC) line-level crossover vs. an active line-level crossover. This led to some rather confused posts before I understood what the HT folk meant by "passive bi-amping" (and a lingering question why anyone would do such a thing).

Or we can agree to disagree, I need to get some sleep.

Great to read posts from a fellow engineer, BTW! - Don

Edit: I am familiar with Murata's (and other's) CM chokes and their benefits; we use them extensively for decoupling and filtering of CM RF noise. Again, a difference in how broad the definition of "ground loop" is in the audio (not RF) world.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
DonH50 is online now  
post #76 of 242 Old 04-26-2019, 09:29 PM
Advanced Member
 
emcdade's Avatar
 
Join Date: Jan 2012
Posts: 981
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 798 Post(s)
Liked: 410
Quote:
Originally Posted by Scotth3886 View Post
"Don't listen to anyone telling you about USB cable can degrade sound. It's either perfect, or it will cut in and out or make strange sound"

This is what I thought too is that it either works or it doesn't. However, any 'strange sounds' in the room are likely me. Thankyouverymuch.
The longer the cable the higher the resistance, and the higher the chance that you will present a degraded squarewave to your DAC. With a deformed squarewave, 0's may be interpreted as 1's and vice versa. At a minimum the DAC's internal electrical noise will be increased interpreting the degraded signal, which may or may not cause it's own problems. It certainly isn't ideal.

Whether this is audible or not will be debated ad infinitum on internet forums. I can only suggest you listen for yourself.

I run my audio at DSD 512 across my server/streamer/dac chain. The chance for errors (including clicks, pops, stutters) is much more likely in my system than someone transmitting 44.1 data so I've taken steps to ensure I don't have noise causing issues at my DAC. I have noticed that my current DAC which has 2 layers of galvanic isolation (at input and also internally before the analog output) seems to be much less sensitive to what source is attached compared to other DACs I've had in my system.
alan0354 and Scotth3886 like this.

Last edited by emcdade; 04-26-2019 at 09:33 PM.
emcdade is online now  
post #77 of 242 Old 04-26-2019, 09:41 PM - Thread Starter
AVS Forum Special Member
 
Scotth3886's Avatar
 
Join Date: Jan 2016
Location: New Albany, OH
Posts: 7,767
Mentioned: 35 Post(s)
Tagged: 0 Thread(s)
Quoted: 3752 Post(s)
Liked: 2300
Quote:
Originally Posted by torii View Post
if any of my laptops had toslink...that would be my choice for music/audio
My Schiit DAC has optical. I wish I had that as an option in my laptop so I can compare
Scotth3886 is online now  
post #78 of 242 Old 04-26-2019, 09:46 PM - Thread Starter
AVS Forum Special Member
 
Scotth3886's Avatar
 
Join Date: Jan 2016
Location: New Albany, OH
Posts: 7,767
Mentioned: 35 Post(s)
Tagged: 0 Thread(s)
Quoted: 3752 Post(s)
Liked: 2300
Quote:
Originally Posted by drewTT View Post
Good time to mention the Audioquest Coffee I am about to order? lol
I honestly thought that the cable wouldn't make any difference in this purely digital function of transferring a digital file from my laptop to the DAC.
Scotth3886 is online now  
post #79 of 242 Old 04-26-2019, 10:10 PM
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 11,749
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 4671 Post(s)
Liked: 3470
Quote:
Originally Posted by markmon1 View Post
Right. You're not going to hear a difference in changing USB cable, regardless what the super expensive cable manufacturers like to claim.
Correct.
m. zillch is offline  
post #80 of 242 Old 04-26-2019, 11:13 PM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by DonH50 View Post
I did not read your post, sorry. Long day. I just responded to @m. zillch .

<pause to read>

I can understand your viewpoint (yes, I have an EE degree; my current day job involves GHz interfaces, and most of my career focused on various data converter and RF circuits from hundreds of MHz to a few hundred GHz). I think we said pretty much the same thing but differ in how broadly we define "ground loop". While anything from DC to light modulating the ground could be properly considered a ground loop, for audio circuits by convention if not by standard (AES) it is limited to the 50/60 Hz current from the incoming (AC) power supply. The RF ground noise, while also a ground loop issue, is deemed RFI in the audio world and considered a separate noise component, at least IME. To an EE that is a distinction without a difference, but to an audio guy (who probably has limited RF experience) it is a big difference. Debugging and fixing a LF ground loop caused by coupled (E or M) field from the AC line is a different thing than dealing with RFI.

This is one of those things that is always gnarly. Technically the datastream on a digital link creates (injects) noise that couples into the receiver. That can occur on the signal (plus, hot) or return (ground) path. I tend to think of RFI as more a noise injector or aggressor rather than a (LF AC) ground loop that follows a much longer path and occurs at a much lower frequency. Thus I treat them differently (repeating above, sorry, end of a 60+ hour work week and as a reward get to work tomorrow (Saturday) since one of my tests is flaking out).

It is probably worth noting that differential (balanced) audio circuits do a pretty good job at handling ground loops (the LF AC type) by facilitating ground isolation since the AC shield is not (or should not be) the AC signal ground. But common-mode rejection falls off rapidly with frequency so even common-mode RF noise will generally be a problem to a differential circuit. We depend upon the isolated shield to "block" RFI from reaching the inner signal pair.

Bottom line is I do not disagree with your broader definition but in practice, at least that I have had in and out of audio, the two are treated differently in the audio world (by audiophiles and design engineers). I had the same problem when I first read about "passive bi-amping" in the context of AVRs: to me, passive bi-amping means a passive (RLC) line-level crossover vs. an active line-level crossover. This led to some rather confused posts before I understood what the HT folk meant by "passive bi-amping" (and a lingering question why anyone would do such a thing).

Or we can agree to disagree, I need to get some sleep.

Great to read posts from a fellow engineer, BTW! - Don

Edit: I am familiar with Murata's (and other's) CM chokes and their benefits; we use them extensively for decoupling and filtering of CM RF noise. Again, a difference in how broad the definition of "ground loop" is in the audio (not RF) world.

Hi Don


Nice to talk to an EE so we can actually get deeper into theory. I looked at your profile, you are an analog IC designer. I was an analog IC designer in 1980s for two years working for a company called Exar Corp. But I was working mainly on bi-polar IC design and the speed was very slow. I know now is CMOS or even more advanced stuffs. My main experience is in systems both analog and digital, mainly high speed circuits ( for my days that is up to 2.5GHz stuffs). I worked a lot on signal integrity for pcb design and big systems.

I designed USB interface before, but that was USB 2 that is only 480MHz stuffs. This is my analysis. We should all know the current loop is the main cause of EMI radiation. EMI flux is proportion to the current through the loop and the area enclosed by the current loop. Ground loop is one form of current loop.
The ground loop current might be RF, but digital signals are random, it can be bursts of signal that can down mix into audible frequency. Also, RF signal can down mix into low frequency and it audible.


Look at my drawing:

1) I drew the transmitting side on left side and I called the ground as GND1. I have a differential driver Tx driving the USB +D and -D through the cable to the receiver Rx on the right side.

2) I put 2 different sources of noise V1 and V2. V2 is the noise on the Tx amp that induce a common mode noise voltage onto +D and -D at the same time. But V2 is not on the ground shield as shown.

3) I put V1 between GND1 and GND2 of the Tx side and Rx side resp. This noise will drive between GND1 and GND2.

4) On the receiver side, there is a Rx amp that receive the differential +D and -D and convert back to single end. The Rx amp should have hysteresis and good common mode rejection ( very common for differential LTP input stage).

5) There are two ways of termination. For USB is 80ohm differential. I have two possibility of terminations, I labeled (A) and (B). For (A), it's just an 80ohm across +D and -D, it's differential termination. This is the most likely case. The other case I labeled (B). It's 40ohm on both +D and -D to GND2. This is not the likely case, 80ohm across +D and -D is the most likely case.

Now, lets look at how V1 and V2 produce current on the ground and on the +D and -D.

1) Let's look at current I2 that caused by V2. In case (A) where 80ohm across +D and -D, the common mode input impedance of the Rx is high, I2 is literally zero. In the case (B) where there is two 40ohm resistor to ground from +D and -D. the noise current produced by V2 will be I2= V2/20ohm= 50mA.( 40ohm//40ohm = 20ohm)

2) Lets look at ground current I1 caused by V1. it will be very large even though V1 is small. I gave an example of V1=0.1V, and resistance between GND1 and GND2 is 0.1ohm, I1 = 1A.

You can see V1 which is the ground noise cause a lot more current flowing through GND1 and GND2. I drew the ground as a big loop as it goes from the Tx through the power cord to Rx. You know EMI produced is proportion to I1 and the area of the loop. That's where all the EMI is generated and affect the circuit.

If you put a ferrite, it can give as high as 50ohm impedance separating GND1 and GND2, so even with V1=0.1V, I1= 0.1/50=20mA. Just a little impedance will go a long way in reducing EMI noise. This EMI noise is completely due to ground loop.

this is my analysis. A lot of noise is cause by random digital noise, that actually can generate audio noise by itself.

Nothing is 100%, I can be wrong, and also, this likely not covering all cases of noise problem. But I think this is very likely the noise problem and it can be verified by just a simple ferrite clip and a minute.


Of cause there's also another possibility that the pcb layout of the transmitter side and the receiver side are so bad that there is ground loop in the transmitter that radiate EMI into the air and the receiver has trace that forms a loop and let the EMI flux cut through the loop and induce current noise and cause the noise in the audio. But the chance of this is smaller. The symptom will be if you move and turn either the transmitter or the receiver to a different position, the noise will change. That would be a good indication the noise is through the air, not the ground loop formed by the USB cable.
Attached Thumbnails
Click image for larger version

Name:	USB ground loop.jpg
Views:	13
Size:	107.9 KB
ID:	2558708  

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.

Last edited by alan0354; 04-27-2019 at 02:11 AM.
alan0354 is offline  
post #81 of 242 Old 04-27-2019, 05:21 AM - Thread Starter
AVS Forum Special Member
 
Scotth3886's Avatar
 
Join Date: Jan 2016
Location: New Albany, OH
Posts: 7,767
Mentioned: 35 Post(s)
Tagged: 0 Thread(s)
Quoted: 3752 Post(s)
Liked: 2300
Quote:
Originally Posted by alan0354 View Post
Hi Don


Nice to talk to an EE so we can actually get deeper into theory. I looked at your profile, you are an analog IC designer. I was an analog IC designer in 1980s for two years working for a company called Exar Corp. But I was working mainly on bi-polar IC design and the speed was very slow. I know now is CMOS or even more advanced stuffs. My main experience is in systems both analog and digital, mainly high speed circuits ( for my days that is up to 2.5GHz stuffs). I worked a lot on signal integrity for pcb design and big systems.

I designed USB interface before, but that was USB 2 that is only 480MHz stuffs. This is my analysis. We should all know the current loop is the main cause of EMI radiation. EMI flux is proportion to the current through the loop and the area enclosed by the current loop. Ground loop is one form of current loop.
The ground loop current might be RF, but digital signals are random, it can be bursts of signal that can down mix into audible frequency. Also, RF signal can down mix into low frequency and it audible.


Look at my drawing:

1) I drew the transmitting side on left side and I called the ground as GND1. I have a differential driver Tx driving the USB +D and -D through the cable to the receiver Rx on the right side.

2) I put 2 different sources of noise V1 and V2. V2 is the noise on the Tx amp that induce a common mode noise voltage onto +D and -D at the same time. But V2 is not on the ground shield as shown.

3) I put V1 between GND1 and GND2 of the Tx side and Rx side resp. This noise will drive between GND1 and GND2.

4) On the receiver side, there is a Rx amp that receive the differential +D and -D and convert back to single end. The Rx amp should have hysteresis and good common mode rejection ( very common for differential LTP input stage).

5) There are two ways of termination. For USB is 80ohm differential. I have two possibility of terminations, I labeled (A) and (B). For (A), it's just an 80ohm across +D and -D, it's differential termination. This is the most likely case. The other case I labeled (B). It's 40ohm on both +D and -D to GND2. This is not the likely case, 80ohm across +D and -D is the most likely case.

Now, lets look at how V1 and V2 produce current on the ground and on the +D and -D.

1) Let's look at current I2 that caused by V2. In case (A) where 80ohm across +D and -D, the common mode input impedance of the Rx is high, I2 is literally zero. In the case (B) where there is two 40ohm resistor to ground from +D and -D. the noise current produced by V2 will be I2= V2/20ohm= 50mA.( 40ohm//40ohm = 20ohm)

2) Lets look at ground current I1 caused by V1. it will be very large even though V1 is small. I gave an example of V1=0.1V, and resistance between GND1 and GND2 is 0.1ohm, I1 = 1A.

You can see V1 which is the ground noise cause a lot more current flowing through GND1 and GND2. I drew the ground as a big loop as it goes from the Tx through the power cord to Rx. You know EMI produced is proportion to I1 and the area of the loop. That's where all the EMI is generated and affect the circuit.

If you put a ferrite, it can give as high as 50ohm impedance separating GND1 and GND2, so even with V1=0.1V, I1= 0.1/50=20mA. Just a little impedance will go a long way in reducing EMI noise. This EMI noise is completely due to ground loop.

this is my analysis. A lot of noise is cause by random digital noise, that actually can generate audio noise by itself.

Nothing is 100%, I can be wrong, and also, this likely not covering all cases of noise problem. But I think this is very likely the noise problem and it can be verified by just a simple ferrite clip and a minute.


Of cause there's also another possibility that the pcb layout of the transmitter side and the receiver side are so bad that there is ground loop in the transmitter that radiate EMI into the air and the receiver has trace that forms a loop and let the EMI flux cut through the loop and induce current noise and cause the noise in the audio. But the chance of this is smaller. The symptom will be if you move and turn either the transmitter or the receiver to a different position, the noise will change. That would be a good indication the noise is through the air, not the ground loop formed by the USB cable.
What exactly does this have to do with the OP's question? Enough of the ferrets!
Ratman likes this.
Scotth3886 is online now  
post #82 of 242 Old 04-27-2019, 08:17 AM
AVS Forum Addicted Member
 
DonH50's Avatar
 
Join Date: Feb 2010
Location: Monument CO
Posts: 12,102
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 3141 Post(s)
Liked: 3099
I need to work today, will be brief. Looked at the very first post then glanced at Alan's picture. Few comments -- please keep in mind this is after a very quick look as I am swamped, may be able to respond better later:


1. There is a length limitation for USB cables. I do not know it off-hand but you can do a search. Too long and signal integrity is compromised by excessive less (signal gets too small) and bandwidth roll-off creates high inter-symbol interference (ISI). Both lead to high jitter (random and deterministic) and can cause bit errors.

2. Within that limitation the manufacturer should not matter as long as the cable meets spec BUT there can be better quality connectors, cable (wire), shielding, etc. A $10 cable might be better in that sense than a $1 cable. I really doubt a $100 (or $1000) cable is going to make any difference.

3. I do not have a lot of experience with USB audio and do not use it in my system at this time. What I have seen in tests and in friend's systems are cases where the PC ground was very noise with lots of HF content. In some DACs (the box audiophiles call a DAC, not the actual DAC IC that I might design) the USB incoming ground is not well isolated from the analog ground on the other side of the DAC. Separating analog and digital grounds is pretty basic stuff for a data converter or mixed signal designer but may get overlooked by a PCB designer. The result is that "digital" ground noise from the USB link is injected onto the "analog" ground and you get a noisy output. I would not call this a ground loop, though there is obviously a current loop in there, but rather noise injection. Noise injection can happen into the ground (return) line, signal line, or both.

4. Noise injected equally into both sides (+ and -) of a differential signal is common-mode noise. The common-mode noise rejection ratio (CMRR) tells you how well such noise is rejected by the receiver (RF, opamp, transformer, whatever). Most opamps have very high CMRR at DC but it falls off rapidly with frequency. Circuits I play with must tolerate CM noise above 10 GHz, but an audio opamp probably has no rejection over 1 MHz or so. Noise at that point can get to the output. Alan's last picture shows a potential ground loop but the cause and effect in my mind is noise from the USB transmitter side injected into the receiver, and unless there is sufficient CMRR at that point the output can be noisy.

5. Isolation, e.g. galvanic isolation, and noise filtering (typically RLC networks, including the ferrites under discussion) can suppress the HF (RFI) the USB transmitter/PC injects into ground and common-mode into the signal pair. If that is the problem then a ferrite can help. Isolation can take the form of active circuits, passive components like transformers or independent coils, optocouplers, etc.

6. If a USB cable includes some sort of isolation and filtering then it could improve the sound if the DAC itself does not sufficiently reject the common-mode and ground noise. To my mind that is the fault of the DAC; other sites have measurements showing that some DACs lack immunity to ground noise. In my world such a design would never fly (literally).

7. A ground loop happens when signal (+) and return (-) currents take different paths. Ideally you want the signal and ground EM fields to be tightly coupled so they flow "together" down the cable. That way any noise happens to both equally and is rejected at the receiving end. If for some reason signal return (ground) is a higher impedance than some other path, like the chassis (safety) ground, then any noise coupled into ground can be amplified. For audio, this is typically 50/60 Hz noise from the AC supply, but of course other things can couple in. The long ground (return) path relative to the signal path means that coupled noise is no longer in phase with the signal and now that difference signal is amplified by the receiver. See e.g. https://www.whatsbestforum.com/threa...1/#post-375417

8. I think of a ground loop as happening when the signal (+) and signal return (-) (ground) currents take different paths. Noise injection happens when signal (+) and signal (-) (return, ground) take the same path but noise is injected into the signal (+), (-), or both. Obviously noise injection can occur in a signal path that has a ground loop.


What we are left with, or at least what I am left with, is two distinct noise sources. Noise (RFI - radio frequency interference) from the USB source coupled onto (injected into) the shield that creates common-mode noise at the receiver. If ground is not properly isolated and/or the receiver's common-mode rejection is not sufficient, then this injected noise can appear at the output. Noise injection does not need a long ground loop; it can occur right at the receiver (inside the box) or anywhere along the line. The second potential source is a ground loop but I tend to think of that as more of an analog signal problem rather than noise injection. Having the signal positive and negative currents take different paths, with ground typically being the longer path (loop), cause signal and ground to get out of phase and now coupled ground noise is amplified. See the linked thread.

When I responded I had the latter in mind and did not realize we were talking about USB cables. In a USB cable you can have either. So, a ferrite bead might help, if the problem is HF noise injection. It will not help if there is an analog ground loop, nor will it help (unless it is very big) if the problem is LF noise on the ground path getting into the analog (output) side of the DAC. Ferrite beads act like inductors, which have rising impedance as frequency goes up, so low at LF and high at HF (to a point). A small'ish ferrite will not generally do much for LF noise such as the 50/60 Hz noise coupled into what I consider and audio ground loop.

HTH - Don

Edit: I used a list but there was no space between items. Switched back to plain old text to add some space for legibility.
18Hurts and Scotth3886 like this.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

Last edited by DonH50; 04-27-2019 at 08:42 AM.
DonH50 is online now  
post #83 of 242 Old 04-27-2019, 08:18 AM
Senior Member
 
Out-Of-Phase's Avatar
 
Join Date: Dec 2017
Posts: 327
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 268 Post(s)
Liked: 189
I wonder if Orange Speaker thinks DSD 512 sounds superior to 16/44.1 FLAC?

In the audiophile world, ignorance truly is bliss. Save your money.
Out-Of-Phase is offline  
post #84 of 242 Old 04-27-2019, 08:48 AM
AVS Forum Special Member
 
Osirus23's Avatar
 
Join Date: Feb 2009
Posts: 1,575
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 214 Post(s)
Liked: 442
Quote:
Originally Posted by Scotth3886 View Post
What exactly does this have to do with the OP's question? Enough of the ferrets!
Your question was answered definitively in the first reply. Now it's just a discussion.
m. zillch likes this.
Osirus23 is offline  
post #85 of 242 Old 04-27-2019, 08:54 AM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by Scotth3886 View Post
What exactly does this have to do with the OP's question? Enough of the ferrets!
Your question was asked and ANSWERED.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
post #86 of 242 Old 04-27-2019, 09:32 AM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by DonH50 View Post
I need to work today, will be brief. Looked at the very first post then glanced at Alan's picture. Few comments -- please keep in mind this is after a very quick look as I am swamped, may be able to respond better later:


1. There is a length limitation for USB cables. I do not know it off-hand but you can do a search. Too long and signal integrity is compromised by excessive less (signal gets too small) and bandwidth roll-off creates high inter-symbol interference (ISI). Both lead to high jitter (random and deterministic) and can cause bit errors.

2. Within that limitation the manufacturer should not matter as long as the cable meets spec BUT there can be better quality connectors, cable (wire), shielding, etc. A $10 cable might be better in that sense than a $1 cable. I really doubt a $100 (or $1000) cable is going to make any difference.

3. I do not have a lot of experience with USB audio and do not use it in my system at this time. What I have seen in tests and in friend's systems are cases where the PC ground was very noise with lots of HF content. In some DACs (the box audiophiles call a DAC, not the actual DAC IC that I might design) the USB incoming ground is not well isolated from the analog ground on the other side of the DAC. Separating analog and digital grounds is pretty basic stuff for a data converter or mixed signal designer but may get overlooked by a PCB designer. The result is that "digital" ground noise from the USB link is injected onto the "analog" ground and you get a noisy output. I would not call this a ground loop, though there is obviously a current loop in there, but rather noise injection. Noise injection can happen into the ground (return) line, signal line, or both.

4. Noise injected equally into both sides (+ and -) of a differential signal is common-mode noise. The common-mode noise rejection ratio (CMRR) tells you how well such noise is rejected by the receiver (RF, opamp, transformer, whatever). Most opamps have very high CMRR at DC but it falls off rapidly with frequency. Circuits I play with must tolerate CM noise above 10 GHz, but an audio opamp probably has no rejection over 1 MHz or so. Noise at that point can get to the output. Alan's last picture shows a potential ground loop but the cause and effect in my mind is noise from the USB transmitter side injected into the receiver, and unless there is sufficient CMRR at that point the output can be noisy.
That's exactly what I presented as with V2 driving the Tx amp and V2 appears on both +D and -D. I would expect the Rx amp that works with RF USB signal will have CMMR in RF speed and have good CMMR.


5. Isolation, e.g. galvanic isolation, and noise filtering (typically RLC networks, including the ferrites under discussion) can suppress the HF (RFI) the USB transmitter/PC injects into ground and common-mode into the signal pair. If that is the problem then a ferrite can help. Isolation can take the form of active circuits, passive components like transformers or independent coils, optocouplers, etc.
That's exactly my point, you don't need much impedance for isolation, a few ohm will reduce the ground current BIG TIME. A single turn with Ferrite will do it. Ferrite is the easiest and cheapest and won't affect performance. It's the first line try. If it doesn't work, then the more exotic fix like you suggested need to be done. I think we are in total agreement here.


6. If a USB cable includes some sort of isolation and filtering then it could improve the sound if the DAC itself does not sufficiently reject the common-mode and ground noise. To my mind that is the fault of the DAC; other sites have measurements showing that some DACs lack immunity to ground noise. In my world such a design would never fly (literally).

7. A ground loop happens when signal (+) and return (-) currents take different paths. Ideally you want the signal and ground EM fields to be tightly coupled so they flow "together" down the cable. That way any noise happens to both equally and is rejected at the receiving end. If for some reason signal return (ground) is a higher impedance than some other path, like the chassis (safety) ground, then any noise coupled into ground can be amplified. For audio, this is typically 50/60 Hz noise from the AC supply, but of course other things can couple in. The long ground (return) path relative to the signal path means that coupled noise is no longer in phase with the signal and now that difference signal is amplified by the receiver. See e.g. https://www.whatsbestforum.com/threa...1/#post-375417

8. I think of a ground loop as happening when the signal (+) and signal return (-) (ground) currents take different paths. Noise injection happens when signal (+) and signal (-) (return, ground) take the same path but noise is injected into the signal (+), (-), or both. Obviously noise injection can occur in a signal path that has a ground loop.
I assume what you mean with (+) is the +D and -D in my example, the (-) is the ground shield of the cable. The signal (+) and return (-) always follows the same path as the current follows the "PATH OF LEAST INDUCTANCE". So the return always come back through the shield, that's not an issue. It's the ground loop current that is not in the (+) that is the problem.

What we are left with, or at least what I am left with, is two distinct noise sources. Noise (RFI - radio frequency interference) from the USB source coupled onto (injected into) the shield that creates common-mode noise at the receiver. If ground is not properly isolated and/or the receiver's common-mode rejection is not sufficient, then this injected noise can appear at the output. Noise injection does not need a long ground loop; it can occur right at the receiver (inside the box) or anywhere along the line. The second potential source is a ground loop but I tend to think of that as more of an analog signal problem rather than noise injection. Having the signal positive and negative currents take different paths, with ground typically being the longer path (loop), cause signal and ground to get out of phase and now coupled ground noise is amplified. See the linked thread.
Your first point is EXACTLY what I was talking about. Just I called it GROUND LOOP. It's the current through the two grounds that forms the loop and the current in the loop create EMI that cause all the noise problem. But just because it's RF doesn't not mean it will not make noise in audio band. Digital signal is random, it can have slow burst of transmission and it will become low frequency audible signal. Also, the digital noise can DOWN MIXED to audible frequency as there are so many harmonics in the digital signal ( randomness, square wave with infinite harmonics etc.).



When I responded I had the latter in mind and did not realize we were talking about USB cables. In a USB cable you can have either. So, a ferrite bead might help, if the problem is HF noise injection. It will not help if there is an analog ground loop, nor will it help (unless it is very big) if the problem is LF noise on the ground path getting into the analog (output) side of the DAC. Ferrite beads act like inductors, which have rising impedance as frequency goes up, so low at LF and high at HF (to a point). A small'ish ferrite will not generally do much for LF noise such as the 50/60 Hz noise coupled into what I consider and audio ground loop.

HTH - Don

Edit: I used a list but there was no space between items. Switched back to plain old text to add some space for legibility.

I think we are mostly in agreement here. I called it GROUND LOOP, you called it RFI, but the mechanism we talked about is the same. Current loop create EM field proportion to the current and the area inside the loop, the EM field will radiate to receiver pcb if the layout is not done correctly. Also, the ground current will cause ground bounce on the Rx end and cause noise.


All I add is the RF signal can down mixed into audible signal and that I suspect is what Torii is hearing.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
post #87 of 242 Old 04-27-2019, 09:36 AM
AVS Forum Addicted Member
 
Ratman's Avatar
 
Join Date: May 2002
Location: Collingswood, N.J.
Posts: 18,901
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 2153 Post(s)
Liked: 2004
EMI/RFI is not "ground loop".
"Noise" is not always "ground loop".
m. zillch and DonH50 like this.



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
Ratman is offline  
post #88 of 242 Old 04-27-2019, 10:26 AM
AVS Forum Addicted Member
 
DonH50's Avatar
 
Join Date: Feb 2010
Location: Monument CO
Posts: 12,102
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 3141 Post(s)
Liked: 3099
USB uses a differential pair, reasonably tightly coupled, so the signal ground return is not through the shield. A differential pair couples to itself so noise in (from) the shield is common-mode. Again, I do not disagree with the basic theory, nor that if RFI is the problem in this case that a ferrite might help, but fundamentally have a different definition of what constitutes a ground loop versus what I consider RFI. I treat and analyze them differently and usually measure them differently. At least in this (audio) context.
Ratman and m. zillch like this.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
DonH50 is online now  
post #89 of 242 Old 04-27-2019, 10:32 AM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by Ratman View Post
EMI/RFI is not "ground loop".
"Noise" is not always "ground loop".

EMI and RFI almost always caused by current loop and mostly through ground.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
post #90 of 242 Old 04-27-2019, 10:37 AM
AVS Forum Special Member
 
alan0354's Avatar
 
Join Date: Oct 2013
Location: Silicon Valley
Posts: 2,257
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked: 418
Quote:
Originally Posted by DonH50 View Post
USB uses a differential pair, reasonably tightly coupled, so the signal ground return is not through the shield. A differential pair couples to itself so noise in (from) the shield is common-mode. Again, I do not disagree with the basic theory, nor that if RFI is the problem in this case that a ferrite might help, but fundamentally have a different definition of what constitutes a ground loop versus what I consider RFI. I treat and analyze them differently and usually measure them differently. At least in this (audio) context.

True, the differential current is not through the shield. The common mode current on the differential pair will be through the shield, but that's small current as shown in V2.


We are just using different terms, I look at it is broad sense, current always forms a loop, even in coax where the return is through the shield, it's a loop....with very small cross section area. It's all about chasing the current path.


I think it's easy for Torii to experiment, if he unplug the laptop and run on battery, if the noise goes away, it's what I called ground loop where current flows between the two grounds. If the noise persist, then it's a different problem. If unplug the laptop fixes the noise, ferrite will help, if not, ferrite is not the solution.

Own designed power amp, own designed preamp, JM LAB Spectral 913.1 speakers, Rythmik F12SE sub.
Not hooked up: Nakamichi Stasis PA-7 power amp, Velodyne VA1210 sub, Kef Reference Series center, Kef Bookshelf speaker, Monitor Audio bookshelf speaker, Infinity rear speakers. Acurus 3X200W amp.
alan0354 is offline  
Sponsored Links
Advertisement
 
Reply 2-Channel Audio

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off