Understanding USB

[mansr]

55 minutes ago, beerandmusic said:

Assuming transmission of a music file can't be done iin same manner, what do you suggest is a "proper cable"?  I mean are you going to suggest that one needs to spend $200 on a cable that meets USB spec???

A proper 6-foot cable need not cost more than $10. You can probably find one for $5 too.

[hdo]

Obviously there are snake oil sellers. Anyway snake oil won't harm you, other than cost you a fortune. If you have money to spend, buy $5 cable and donate the rest to charities. You won't lose any sound quality. But you become a good man!

[beerandmusic]

1 hour ago, mansr said:

A proper 6-foot cable need not cost more than $10. You can probably find one for $5 too.

thank you, i trust everything you have said as factual. 

I do believe more expensive cables "may" help where older non-modern dacs may not have properly isolated noise, but I believe that in a well designed modern dac with noise isolation, that neither the cable or the hardware source really matters much, if at all, anymore.

[fas42]

1 hour ago, beerandmusic said:

thank you, i trust everything you have said as factual. 

I do believe more expensive cables "may" help where older non-modern dacs may not have properly isolated noise, but I believe that in a well designed modern dac with noise isolation, that neither the cable or the hardware source really matters much, if at all, anymore.

 

Depends upon how fussy one is about the quality of reproduction - in the realm that I'm interested in, one needs to be 'fanatical' about every tiny aspect of the system and its environment, to achieve and maintain that level - if one is happy with a "lower standard" then there would be plenty of components, casually set up, that would do the job ...

[GUTB]

USB is an awful audio transport medium -- it's just the only option for very high-rez audio. USB was not designed for audio in mind. It's 5v line is very noisy. There is no power quality requirement, no shielding requirement and no manufacturer standard for cable impedance. The el-cheapo USB cables are designed to work reliably up to 5-6 feet, and anything more is out the window. Infested with dirty power, conducting EMI, impedance mis-matching, etc -- who cares. High quality USB cables are at least built to ensure a reliable 90 Ohms, isolation of the 5v line from the data lines, and good shielding against EMI.

 

A robust USB chain however must include some means to filter out noise from getting into the cable to begin with. The use of linear PSUs and various connector filters on the motherboard is one way (I use a PP OCXO USB controller externally powered off a 5v battery). USB conditioners and isolators are another way.

 

1. A linear PSU will generate much lower ripple than even the best low-ripple ATX power supplies. Also, linear PSUs are less likely to cause ground loops.

2. Elimination of electrical noise from the motherboard's power rails through SATA filters, elimination of fans and the like. I just power my SSD externally into a separate power circuit to completely eliminate SSD power noise from ever getting into the audio circuit. Also there is not a single fan anywhere in my audio PC.

3. Tuning of the OS for dedicated audio use -- reduces self-noise generated by the computer running uneeded tasks.

4. Use of an audiophile-grade USB controller either externally powered like mine, or internally powered from a clean source. Audiophile-grade USB controllers have advanced clocks that will ensure a very high quality transmission. A pristine clock edge means less work for the DAC controller.

5. Isolation of USB from the DAC altogether through various methods -- optical bridging, LAN bridging, DDCs, etc.

 

These tactics should go together to form a strategy. It takes time, learning, and some cost, but the gains are large and should not be overlooked. To see immediate gains right away, start with a USB filter / isolator and once you experience the SQ boost and then realize what you thought you knew about digital audio is false you will be emotionally prepared to take the plunge.

 

 

[nbpf]

8 hours ago, beerandmusic said:

who said anything about a whole album...there is no need for that...you can just buffer a few packets, or whatever is necessary to ensure 100% accuracy....Whatever method is used for EC need not wait for an entire album..that would be ridiculous.

I said a whole album if you carefully read my post. As explained by other contributors, see also previous post, the problems that affect decoding USB streams have little to do with accuracy or, conversely, transmission errors. Isolators, recklockers, purifiers and other fancy devices and techniques aim at reducing RF interferences, eliminating current leaks, ground loops, converting a USB stream into a SPDIF stream, etc. They do not tackle transmission errors directly simply because these are extremely rare and have little impact on sound quality. Isolators, reclockers, etc. work very well but they can only alleviate the above mentioned problems. Transferring whole albums (or, indeed, playlists) to a DAC's internal memory before starting replay (and using standard file transfer protocols with error correction algorithms and data integrity checks) would be a means of eliminating the problems. The DAC could in principle shut down its network or USB interface before starting replay and no incoming stream would be managed (buffered, encoded, etc.) at replay time. The disadvantage, as I mentioned, is that users would have to wait a little bit before the music starts playing, like in an old jukebox. But they could throw away all their isolators, decrapifiers, converters, etc. They would not be needed anymore.

[hdo]

6 hours ago, GUTB said:

 

USB is an awful audio transport medium

 

 

Yes only if USB is used as analog transport. When used as digital, it's 100% good. That's why you can save data into USB devices without worrying about transmission errors. USB is more than adequate for audio. I don't have any problem sending 32bit 384khz data over USB. There is no problem with USB. It's only poorly developed DACs blame USB.

[Speed Racer]

2 hours ago, hdo said:

 

Yes only if USB is used as analog transport. When used as digital, it's 100% good. That's why you can save data into USB devices without worrying about transmission errors. USB is more than adequate for audio. I don't have any problem sending 32bit 384khz data over USB. There is no problem with USB. It's only poorly developed DACs blame USB.

 

USB is never used as an analog transport. That would be impossible. It only transports digital data.

[mansr]

7 minutes ago, Speed Racer said:

USB is never used as an analog transport. That would be impossible. It only transports digital data.

A USB cable can of course be used as an analogue interconnect. I should try it and see what happens.

[beerandmusic]

11 hours ago, fas42 said:

 

Depends upon how fussy one is about the quality of reproduction - in the realm that I'm interested in, one needs to be 'fanatical' about every tiny aspect of the system and its environment, to achieve and maintain that level - if one is happy with a "lower standard" then there would be plenty of components, casually set up, that would do the job ...

 

i believe the digital realm is absolute and cannot be improved on anymore.

 

[pkane2001]

6 hours ago, nbpf said:

the problems that affect decoding USB streams have little to do with accuracy or, conversely, transmission errors. Isolators, recklockers, purifiers and other fancy devices and techniques aim at reducing RF interferences, eliminating current leaks, ground loops, converting a USB stream into a SPDIF stream, etc. 

 

For most competently designed DACs this is not an issue. What you are describing is noise leaking into the DAC through the USB connection. This should be measurable, but is not in quality DACs (even the inexpensive ones), even with the most sensitive equipment. Why? Most likely because this is a solved problem, and not because we have not figured out how to measure it.

 

What is true is that some of these claimed cleanup/isolator/reclocker devices introduce their own noise signature into the DAC, and that part is measurable and has been demonstrated.

[beerandmusic]

10 hours ago, GUTB said:

USB is an awful audio transport medium -- it's just the only option for very high-rez audio. USB was not designed for audio in mind. It's 5v line is very noisy. There is no power quality requirement, no shielding requirement and no manufacturer standard for cable impedance. The el-cheapo USB cables are designed to work reliably up to 5-6 feet, and anything more is out the window. Infested with dirty power, conducting EMI, impedance mis-matching, etc -- who cares. High quality USB cables are at least built to ensure a reliable 90 Ohms, isolation of the 5v line from the data lines, and good shielding against EMI.

 

 

 

I have a SHORT usb spec audioquest forest cable that i bought used for $20...I do not believe any cable will offer any improvement in SQ given my optoisolation dac. 

[beerandmusic]

6 hours ago, nbpf said:

I said a whole album if you carefully read my post.

 

I know YOU did...i am saying i did not...and I believe that would be ludicrous to buffer an entire album because a much smaller buffer is MORE than enough.  I do not believe you need to transfer an entire album to alleviate usb inherent issues.

[lucretius]

1 hour ago, beerandmusic said:

 

i believe the digital realm is absolute and cannot be improved on anymore.

 

 

 I could scarcely fathom this idea. E.g. what about new semiconductor material, quantum computers, etc?

[Fitzcaraldo215]

16 hours ago, unbalanced output said:

If you have a little extra budget, try a Regen or isolator type of device between the computer usb and the DAC and try for yourself. You may be surprised with the difference.

Or, if you do the comparison properly - blind or double blind - you may be surprised that there is no worthwhile difference. 

[GUTB]

52 minutes ago, Fitzcaraldo215 said:

Or, if you do the comparison properly - blind or double blind - you may be surprised that there is no worthwhile difference. 

 

 

 

[nbpf]

3 hours ago, beerandmusic said:

 

I know YOU did...i am saying i did not...and I believe that would be ludicrous to buffer an entire album because a much smaller buffer is MORE than enough.  I do not believe you need to transfer an entire album to alleviate usb inherent issues.

More than enough for what? If you read my post carefully, you will realize that I have not argued that one need to transfer an entire album to alleviate USB issues. Rather, I have argued that one can eliminate such issues by switching off data transfer before starting decoding. This is, in my view, hardly debatable.

[nbpf]

3 hours ago, pkane2001 said:

 

For most competently designed DACs this is not an issue. What you are describing is noise leaking into the DAC through the USB connection. This should be measurable, but is not in quality DACs (even the inexpensive ones), even with the most sensitive equipment. Why? Most likely because this is a solved problem, and not because we have not figured out how to measure it.

 

What is true is that some of these claimed cleanup/isolator/reclocker devices introduce their own noise signature into the DAC, and that part is measurable and has been demonstrated.

Perhaps you are right. But I have a rather old Naim DAC and I have found it to be quite sensitive to the quality of the incoming SPDIF stream.

[pkane2001]

18 minutes ago, nbpf said:

Perhaps you are right. But I have a rather old Naim DAC and I have found it to be quite sensitive to the quality of the incoming SPDIF stream.

There's a big difference between SPDIF and USB. SPDIF signal carries with it the clock that's used to time the samples at the output of the DAC. This can easily lead to jitter if the source clock isn't good, the cable distorts the signal, or the clock recovery isn't done well.

 

With USB, the clock responsible for timing DAC output is located at the DAC. The USB cable, source clock, and the clock recovery mechanisms are all irrelevant. The relevant things are the noise isolation in the USB receiver, and the quality of the internal DAC clock. 

[Ralf11]

6 hours ago, pkane2001 said:

 

For most competently designed DACs this is not an issue. What you are describing is noise leaking into the DAC through the USB connection. This should be measurable, but is not in quality DACs (even the inexpensive ones), even with the most sensitive equipment. Why? Most likely because this is a solved problem, and not because we have not figured out how to measure it.

 

What is true is that some of these claimed cleanup/isolator/reclocker devices introduce their own noise signature into the DAC, and that part is measurable and has been demonstrated.

 

if so, then what accounts for the large number of (informal listening sessions / not real tests) where people greatly prefer DACs like the Chord Dave, etc. ?

 

Is it the analog stage(s) or is it all conf. bias?

[pkane2001]

1 minute ago, Ralf11 said:

 

if so, then what accounts for the large number of (informal listening sessions / not real tests) where people greatly prefer DACs like the Chord Dave, etc. ?

 

Is it the analog stage(s) or is it all conf. bias?

 

Possibly both?

 

[Speed Racer]

pkane2001 would have you believe that a $500 run of the mill sigma-delta DAC sounds just as good or better than a higher end DAC like Yggdrasil. Don’t believe it....

[mansr]

4 minutes ago, Speed Racer said:

pkane2001 would have you believe that a $500 run of the mill sigma-delta DAC sounds just as good or better than a higher DAC like Yggdrasil. Don’t believe it....

Why not?

[Speed Racer]

Because it is not true!

[pkane2001]

7 minutes ago, Speed Racer said:

Because it is not true!

 

Because you say so?