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post #91 of 242 Old 04-27-2019, 10:40 AM
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There is always a current loop. In a ground loop the current loop of interest is through two different ground paths.
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post #92 of 242 Old 04-27-2019, 10:47 AM
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Originally Posted by DonH50 View Post
I need to work today, will be brief. ...........................

That's the reason I retired at 52, 14 year ago. I love electronics, but the long hours and the politics that I don't miss. It's like working 60hr/week. 4 years ago, my former called me to do a contract to design the front end of the next generation semiconductor analytical instrument( similar to mass spectrometer). I could work at home. I worked for a year and half, then the upper management want to outsource the pcb layout to subcontractor!!! The CTO strongly disagree, those subcontractor are useless, we had to hold their hands every inch of the way. But upper management over ruled the CTO. I just quit, I don't need the headache dealing with the subcontractor and back to retirement. The job is fun, just cannot stand the politics.


Electronics is still my passion, after retiring, I still spent a few years studying electromagnetics, antenna and all. Now I design power amplifiers as a hobby. Just don't want to work anymore.

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post #93 of 242 Old 04-27-2019, 10:48 AM
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Originally Posted by DonH50 View Post
There is always a current loop. In a ground loop the current loop of interest is through two different ground paths.

It's the unwanted path that cause the problem. Anyway, we are getting in semantics.

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post #94 of 242 Old 04-27-2019, 11:20 AM
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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.
I have to agree here. While a ground loop can certainly occur at any frequency, Ferrite beads or cores are mostly ineffective at 60hz. As an EE in the broadcast field I have seen ground loops with very high power RF in television transmission. I even once had an issue in an older studio facility where the 3.58mhz color subcarrier signal, which was distributed at 2vpp into 75ohms, was causing a ground loop which dumped 3.58mhz on the chassis ground.

But when we talk of ground loops in any field of audio, it's most usually 60hz. Ferrite cores on cables are for RFI, and mainly for egress issues. Remember products these days must meet stricter FCC and other world EMI/RFI radiation limits.
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post #95 of 242 Old 04-27-2019, 11:36 AM
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Now I start to understand the disagreement more. People here consider RFI and audio noise are totally different issue and they are not related. I don't think this is true. RF can down mixed and do a lot of funny things, one cannot just say it's RF so it's not going to make audible noise. Also, the transmission can be in bursts, the each burst can happen in audio frequency range. Digital noise is totally random depending on how the interface is programed to do. One cannot assume they can never interfere into audio range.

Of cause, ferrites will not work at 60Hz, I think I said it many times already.


In the specific noise issue from Torii, it's easy to find out, unplug the laptop from the AC power and let it run on battery, if the noise goes away, it's the ground noise through the cable. If not, it's something else.

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post #96 of 242 Old 04-27-2019, 12:37 PM
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I don't think anybody is denying that RFI can be mixed or demodulated to audio. But the root cause in that case is the RFI, not what we are calling a ground loop.

From my first post on this:

Quote:
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.

Need to get back to work...
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post #97 of 242 Old 04-27-2019, 12:46 PM
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Quote:
Originally Posted by DonH50 View Post
I don't think anybody is denying that RFI can be mixed or demodulated to audio. But the root cause in that case is the RFI, not what we are calling a ground loop.

From my first post on this:




Need to get back to work...
Ha ha, wait until you get back from work!!!


I really think at this point, we are not disagreeing other than what to call. You can call RFI, I can call ground loop. Both can cause EMI.


To be honest, we might be talking about something that is not even apply to Torii, Noise is a funny thing, one can never be too sure. All I can say is Ferrite will have about 50% chance to fix his problem. But 50% is quite good as first try.

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post #98 of 242 Old 04-27-2019, 01:06 PM
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Quote:
Originally Posted by alan0354 View Post
All I can say is Ferrite will have about 50% chance to fix his problem. But 50% is quite good as first try.
Can't argue that logic!
Or the same odds with:
A new cable
A new laptop
A different AC source
A different DAC
A different power cable with the laptop
A different power cable with the DAC
A Faraday shield
Etc.



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post #99 of 242 Old 04-27-2019, 01:10 PM
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Originally Posted by Ratman View Post
Can't argue that logic!
Or the same odds with:
A new cable
A new laptop
A different AC source
A different DAC
A different power cable with the laptop
A different power cable with the DAC
A Faraday shield
Etc.
But this is the cheapest fix.


The cheapest way is unplug the laptop, run on battery, if the noise goes away, then I have more confident ferrite will work. If noise still persists, then we are just blowing hot air so far. I said it a lot of times, noise is tricky business, nobody can be sure until one tries it.


We have not pass the starting gate, one step at a time.


No, power cable will NOT make a difference.
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post #100 of 242 Old 04-27-2019, 01:22 PM
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Quote:
Originally Posted by alan0354 View Post
No, power cable will NOT make a difference.
You never know. Can't hurt to try. It's a 50/50 shot!
And IMO... we are well past the starting gate after ~100 posts/responses.



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post #101 of 242 Old 04-27-2019, 01:25 PM
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battery power on laptop fixes alot of noise for me

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post #102 of 242 Old 04-27-2019, 01:45 PM
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Now for the ferrite choke test!
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post #103 of 242 Old 04-27-2019, 02:07 PM
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Quote:
Originally Posted by torii View Post
battery power on laptop fixes alot of noise for me
Then you have a better chance getting the USB cable with ferrite to improve the noise.


But you say only fixes a lot, not all? That point to me that one of the component has problem other than just ground loop. Next step is switch computer if you have another one. You have to be more specific what hook up to what.

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post #104 of 242 Old 04-27-2019, 02:08 PM
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Originally Posted by Ratman View Post
Now for the ferrite choke test!
It is now, unplug the laptop helps.

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post #105 of 242 Old 04-27-2019, 02:10 PM
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My notebook, used to run Dirac Live and make various measurements using REW and some other analysis SW, introduces a ground loop when I hook it up to my processor. Use a cheater plug or just unplug it and let it run on battery power and the noise goes away. Does not matter if I use HDMI or analog (RCA) cables. That is what I consider a ground loop.

I have a monitor that creates a buzz in my desktop speakers. Ground isolation is not the issue there, but adding a ferrite choke on the monitor's video cable killed the buzz.

I could not say if the noise from a USB connection in any given case is a ground loop or RFI (using my definitions which are clearly not universal). If we are talking about a notebook PC, I would unplug it and see if the problem goes away when running on battery power. If so a ground loop is the likely culprit; if not, try the ferrite choke. If some other component, a ground lift adapter (cheater plug) is an easy quick test for a ground loop but not good as a long-term solution (not safe). If it is a ground loop, there are simple passive devices to fix it, including isolation transformers, cable (RF cable) isolators, DI boxes, etc.

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post #106 of 242 Old 04-27-2019, 02:15 PM - Thread Starter
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Originally Posted by Osirus23 View Post
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.
From looking at post 82, (1) maybe it wasn't answered in the first reply. The cable I'm trying to use is 4 meters. Is it an issue or is it not?
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post #107 of 242 Old 04-27-2019, 02:19 PM
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Originally Posted by Scotth3886 View Post
From looking at post 82, (1) maybe it wasn't answered in the first reply. The cable I'm trying to use is 4 meters. Is it an issue or is it not?

Your original question was answered both the link to the Physics and the fact you can buy 15ft long USB3 cables I linked to Amazon.


We are talking about the noise problem for Torii, nothing to do with you unless you have noise problem. Then you can join in and try to troubleshoot the noise.

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post #108 of 242 Old 04-27-2019, 02:33 PM
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I might try new usb cable after I play around this summer with new maggie lrs. I was just trying to add to thread about maybe a usb cable can matter for scott.


the laptops I use create noise...if a cable can fix that...then usb cables may help

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post #109 of 242 Old 04-27-2019, 02:35 PM
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Quote:
Originally Posted by Scotth3886 View Post
From looking at post 82, (1) maybe it wasn't answered in the first reply. The cable I'm trying to use is 4 meters. Is it an issue or is it not?
Quote:
Originally Posted by alan0354 View Post
Your original question was answered both the link to the Physics and the fact you can buy 15ft long USB3 cables I linked to Amazon.


We are talking about the noise problem for Torii, nothing to do with you unless you have noise problem. Then you can join in and try to troubleshoot the noise.
Scott,
You are the opening poster of this thread. It's a darned shame you don't have a say in this conversation anymore. Wow!



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post #110 of 242 Old 04-27-2019, 02:42 PM
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I say usb cables may matter...based on my experiences...so if I answered scotts question would be the length is ok, but it may have noise issues...now whether the cable itself can fix the noise is whats debated.

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post #111 of 242 Old 04-27-2019, 03:04 PM - Thread Starter
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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.

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.

"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."


By "compromised" does it just stop working or is sound quality degraded before it gets to the point that it stops? Would it be advantageous to use a much shorter USB cable and longer RCAs?

My 'friend', who I got in several arguments with thinks the cable "is not letting all of the information through". I said fine, let's level match and AB cables. He blows up at even the mention of blind, level matched testing so he refused to help me when I really wanted to know. I wasn't setting him up or anything. He said the replacement cable sounded much better and I said it sounded the same so I said let's see if you could identify it when you can't see what's being used. That's the trigger.

True, I am a subjectivist audiophile, but nothing like he is. He's probably got more money in cables than I've ever had in a system. However, I don't trust my audio memory so a rapid A vs B is useful to me. And I understand 'level matched' or there's a detectable difference right there. And I also understand NOT seeing what your testing. So my subjectivism is not quite as extreme as his.

The overriding issue is that I'm still not completely pleased with the sound of Tidal, especially on a piece with piano. We went back to vinyl several times and what a relief, but I don't buy it that there's still that much difference after almost 40 years of digital.
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post #112 of 242 Old 04-27-2019, 03:14 PM
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Originally Posted by Scotth3886 View Post
Can there be a sound quality difference with a USB cable from laptop to my DAC if I'm using a longer (4 meter) cable from laptop to DAC versus a shorter cable?

I have the new DAC over on the equipment rack, but I like to use the laptop as a LAPtop so I can get some work done while listening. I thought as long as it works, you were getting the best sound quality possible, and if it didn't work, it buffers and cut out, etc. That it's all or nothing. Am I correct on this?
I had some rearranging to do, so I moved from a high quality 3Ft. USB cable to a 15ft. USB from my HomeTheaterPC to DAC.
I can't hear any difference. Sounds as good as always.
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post #113 of 242 Old 04-27-2019, 03:18 PM
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a short under 4 ft usb cable with longer rca's is something I would rather use vs a longer usb

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post #114 of 242 Old 04-27-2019, 03:20 PM - Thread Starter
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Originally Posted by alan0354 View Post
Your original question was answered both the link to the Physics and the fact you can buy 15ft long USB3 cables I linked to Amazon.


We are talking about the noise problem for Torii, nothing to do with you unless you have noise problem. Then you can join in and try to troubleshoot the noise.

Don't you dare tell me when I can or cannot join in on a thread I started to solve an issue. Torri can start his own thread.

Anyway, these are Audioquest USB2 cables terminating in a micro USB at the DAC. Audioquest because it was the only cable I could lay my hands on looking around locally.

I use my laptop on and off battery … no difference in a room with a noise floor of 18db. My issue is the sound (of the music, the notes, especially on piano) are still a bit hard. it's enough of a distraction that it doesn't allow me to really enjoy what I'm listening to. Something still isn't right, whether it be laptop, cable, connectors, DAC or something. Maybe, it's just the way Tidal is? That's the reason for my OP in this thread.
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post #115 of 242 Old 04-27-2019, 03:24 PM
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good read by science community forum i suppose. https://www.audiosciencereview.com/f...-discuss.5899/

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post #116 of 242 Old 04-27-2019, 03:26 PM
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Hi Scott,

This is a new place for us to meet...

Based on a very quick look at the specs, USB 2 had a 5 m (~15') limit and there is no limit specified in the USB 3 spec. Please keep in mind that I am no expert on the USB protocol and may not have the latest specs. The information I have for our USB transceivers (the ones used on our eval and production boards) recommends no more than 3 m for a USB 3.0 cable.

Modern DACs reclock the data so are pretty immune to jitter or other signal integrity issues until the link bit error rate gets too high to correct. The sound could get "glitchy" or drop out, I would think. Depends on how the DAC handles the errors. Generally speaking I can't see how the cable would change the "tone" or "timbre" of the sound; the bits don't work that way. IME, an important qualification, you either get a solid signal or get glitches (staticy noise) and dropouts (bursts of silence). As mentioned earlier, bad DAC interfaces, cables with a bad ground (shield), can generate noise that typically sounds like a hum or raspy buzz. If the sound is quiet in the quiet/silent passages and you do not hear any static or dropouts the cable is fine.

All IME/IMO - Don
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post #117 of 242 Old 04-27-2019, 03:31 PM - Thread Starter
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Originally Posted by torii View Post
a short under 4 ft usb cable with longer rca's is something I would rather use vs a longer usb

Ok, maybe that's worth trying. The DFR was in the USB port in my laptop connected to the integrated by long RCAs. I'm trying to keep my laptop in my LAP so I can do a little work while I'm listening, which means long something to get 'it' over to my Hegel. I did get an improvement (level matched, blind tested) with my Schiit DAC vs the DFR, but still not enough. My friend thought (strongly) that using a regular old USB to micro USB cable was the issue so we got in the car and started from store to store for several hours to find one. Since it was his idea, of course he 'heard' a difference, but I didn't. So I said: "since you heard a difference, let's test that". Perfectly reasonable to me as again, I wasn't trying to set anyone up, but trying to find the answer. Since there seems to be a limit on cable length, and I'm right up on it, I wasn't quite done examining this yet.
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post #118 of 242 Old 04-27-2019, 03:37 PM
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Originally Posted by Scotth3886 View Post
Don't you dare tell me when I can or cannot join in on a thread I started to solve an issue. Torri can start his own thread.

Anyway, these are Audioquest USB2 cables terminating in a micro USB at the DAC. Audioquest because it was the only cable I could lay my hands on looking around locally.

I use my laptop on and off battery … no difference in a room with a noise floor of 18db. My issue is the sound (of the music, the notes, especially on piano) are still a bit hard. it's enough of a distraction that it doesn't allow me to really enjoy what I'm listening to. Something still isn't right, whether it be laptop, cable, connectors, DAC or something. Maybe, it's just the way Tidal is? That's the reason for my OP in this thread.
You are the one that complain why we gone onto ferrites. Hey, I've been going out of my way to help you, even spend the time to go on Physics Forums to ask for you to give you the answer. I don't deserve this in return.


Everyone here told you long cable will not gradually degrade the sound, it's either working or not working. If the long USB cable works, better to use short RCA cables.

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Last edited by alan0354; 04-27-2019 at 03:44 PM.
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post #119 of 242 Old 04-27-2019, 03:43 PM - Thread Starter
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Quote:
Originally Posted by DonH50 View Post
Hi Scott,

This is a new place for us to meet...

Based on a very quick look at the specs, USB 2 had a 5 m (~15') limit and there is no limit specified in the USB 3 spec. Please keep in mind that I am no expert on the USB protocol and may not have the latest specs. The information I have for our USB transceivers (the ones used on our eval and production boards) recommends no more than 3 m for a USB 3.0 cable.

Modern DACs reclock the data so are pretty immune to jitter or other signal integrity issues until the link bit error rate gets too high to correct. The sound could get "glitchy" or drop out, I would think. Depends on how the DAC handles the errors. Generally speaking I can't see how the cable would change the "tone" or "timbre" of the sound; the bits don't work that way. IME, an important qualification, you either get a solid signal or get glitches (staticy noise) and dropouts (bursts of silence). As mentioned earlier, bad DAC interfaces, cables with a bad ground (shield), can generate noise that typically sounds like a hum or raspy buzz. If the sound is quiet in the quiet/silent passages and you do not hear any static or dropouts the cable is fine.

All IME/IMO - Don

I just checked the box the cable came in. I'm mistaken. It is a 5 meter so I'm right on the limit. Plus never any dropouts, static or anything like that. It's as dead silent as the room, which is very quiet.

"I can't see how the cable would change the "tone" or "timbre" of the sound"

Now you're at my issue / concern. I don't see how it could either. Six day of arguing with him had me rechecking my thoughts and having doubts. I know 'sounds the same is really threatening to him', but this is the guy I did the single blind speaker cable and amp (VTL300 vs ARC Classic 150) comparisons 25 years or so ago, and we found differences, but I could never decide on which of the two very different sounding mono blocks I liked best.

He shouldn't feel threatened by this.
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post #120 of 242 Old 04-27-2019, 03:44 PM
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if using tidal on laptop, I get around no usb cables by using the blesound node over wifi. Im getting noise(very subtle/minor) from laptop to dac to amp for headphone use. like I said, for main system I use bluesound node over wifi. my headphone systems are a lot more resolving than my speakers unfortunately.

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