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barnept

Ethernet, USB, Optical or Coax to my DAC??

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barnept   

Hello.

 

I am confused about what is the best means (sound quality wise) of moving digital music files to a DAC. I read all about USB DACs using asynchronous connections so that the DAC takes over clock duties from the Pc (is that something to do with jitter?), how the various types of connections can be limited in the music file's maximum bit depth and sampling frequency etc etc. How does ethernet fare up sound quality wise? I assume it is unlimited when it comes to the music file's bit depth and sampling frequency, but what about jitter, clock ownership?

 

Please, can someone out there tell me what the best connection is, technically? I am assuming that the best connection technically will also be the best connection for outright sound quality??

 

Many thanks.

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barrows   

USB, Ethernet, and Firewire are all asynchronous interfaces where the DAC clock is the "master". All three of those interfaces have the ability to be essentially "perfect" in technical terms of getting the data to the DAC chip. But, how well they are implemented will make for differences in performance. SPDIF interfaces (optical, coax, AES) are technically inferior as the embedded clock must be extracted, and then its differences with the DAC clock have to resolved. But, a really good SPDIF implementation can trump a poor USB implementation.

If you are DAC shopping, my advice would be to choose a DAC with a really good USB interface built in. Read reviews, and try and learn about the technical differences between USB implementations. There is no easy answer to this question, as the implementation of any interface can make a difference with its performance.

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CatManDo   

Ethernet, USB, Optical or Coax to my DAC??

 

I am confused about what is the best means (sound quality wise) of moving digital music files to a DAC.

 

A DAC doesn't play files, it processes a digital data stream from a source that plays the files. If the device has a network connection, then it's not a DAC but a streamer.

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Allan F   
A DAC doesn't play files, it processes a digital data stream from a source that plays the files. If the device has a network connection, then it's not a DAC but a streamer.

 

Given the reason for his question, your comment is a distinction without a difference.

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Hiro   

I have recently stumbled upon this interesting post by iFi Audio that explains the benefits of their USB iPurifier, and it got me thinking how the situation looks like in the case of Ethernet connection...

 

Does anybody know if the Ethernet signal needs to be purified in the same fashion as USB, or is it cleaner to begin with?

 

purifier.png

 

iDSD micro Crowd-Design. HiFi Man HE-6 takes on the Meaty Monster! (page 82) - Page 76

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alan_un   
A DAC doesn't play files, it processes a digital data stream from a source that plays the files. If the device has a network connection, then it's not a DAC but a streamer.

 

Actually, I know of at least one DAC with an Ethernet connection, the Merging Technology Horus, which is not a streaming device.

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fmak   
I have recently stumbled upon this interesting post by iFi Audio that explains the benefits of their USB iPurifier, and it got me thinking how the situation looks like in the case of Ethernet connection...

 

Does anybody know if the Ethernet signal needs to be purified in the same fashion as USB, or is it cleaner to begin with?

 

[ATTACH=CONFIG]13500[/ATTACH]

 

iDSD micro Crowd-Design. HiFi Man HE-6 takes on the Meaty Monster! (page 82) - Page 76

 

These are a joke and are cartoon illustrations to get you to buy one.

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fmak   
These are not actual eye patterns. Certainly the IFI does clean the signal (and I own one) but it will not be perfect after the device.

 

These seem to be a feature of iFi promotional material and are not the real thing with ringing, asymmetry and other warts.

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Hiro   

OK, so the iFi purifier is going to clean up the signal, but only up to a point?

 

Anyway, I know that Schiit has a similar? USB decrapifier (as they call it) on offer, and other companies go to great lengths as well to minimize the problems with USB transmission. I guess my question still stands then:

 

Does anybody know if the Ethernet signal needs to be purified in the same fashion as USB, or is it cleaner to begin with?

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4est   

Needs? Most likely it could use it to some lesser extent.

Does anybody know if the Ethernet signal needs to be purified in the same fashion as USB, or is it cleaner to begin with?

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Does anybody know if the Ethernet signal needs to be purified in the same fashion as USB, or is it cleaner to begin with?

 

[ATTACH=CONFIG]13500[/ATTACH]

 

iDSD micro Crowd-Design. HiFi Man HE-6 takes on the Meaty Monster! (page 82) - Page 76

 

No Ethernet doesn't need 'purified'.

 

Try this: Install JRiver. Adjust it's prebuffer from it's default 6 seconds to 20 seconds. Start playing your file. Wait 3 seconds and pause your playback.

 

Pull your Ethernet cable or disconnect from your wifi network.

 

Press play and let me know if you are playing from buffer or from your Ethernet cable.

 

Ethernet and up stream application error checking and correction will have made sure that the data is error free.

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Hiro   
They would have displayed screenshots from a real scope.... Not some cartoonist illustration.

 

I admit the sort of measurement would be preferable, but if the their graph correctly represents the distortion on the unfiltered USB signal, then I don't see a problem with it.

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Hiro   
No Ethernet doesn't need 'purified'.

 

...

 

Ethernet and up stream application error checking and correction will have made sure that the data is error free.

 

This leads me to conclude that ethernet may be the best interface for computer audio purposes after all. Thanks for the information.

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4est   

I find HM's statement very telling:"Ethernet and up stream application error checking and correction will have made sure that the data is error free."

 

If the data were getting fouled in this manner, you'd hear drop outs or other obvious artifacts.

 

 

 

This leads me to conclude that ethernet may be the best interface for computer audio purposes after all. Thanks for the information.

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Harpy   
SPDIF interfaces (optical, coax, AES) are technically inferior as the embedded clock must be extracted, and then its differences with the DAC clock have to resolved.

 

If you have and external converter and the USB goes through the clock, is it reclocked again for SPIF conversion? Would this been done by the converter or DAC? I never been clear on this point.

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tranz   
No Ethernet doesn't need 'purified'...

 

Do not agree, but it does depend on the hardware setup and implementation.

 

USB - copper lines with ground

LAN - copper lines with ground

 

I see the error correction benefit of LAN over USB for audio, but electrical

noise (e.g. common mode) will still travel downstream and still needs to be addressed. Even though it is still bit perfect, this noise will/can irritate.

 

Simple trials/experiments to see the effect:

 

- try a filter like Accoustic Revive,

- try an optical isolator or extender powered by LPSU

- try powering the switch with an LPSU,

- try having no other traffic or gadgets with switching supplies connected to the switch used for audio (e.g. Cable box, other computers)

 

Cheers

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If you have and external converter and the USB goes through the clock, is it reclocked again for SPIF conversion? Would this been done by the converter or DAC? I never been clear on this point.

 

In an S/PDIF system (in any of its flavors) the source is in charge of the clocking. The DAC has to either synchronize itself to the source or use an ASRC (asynchronous sample rate converter) to resample to a local clock. There are many forms of synchronizing circuits out there with varying degrees of output jitter. The best ones can be quite good but are pretty rare.

 

The "clocking" at the source is from whatever is sending out the S/PDIF signal. In the case of a USB->S/PDIF converter, which uses "asynchronous" USB protocol, the clock is in the converter. The USB asynch means the computer is synced to the converter, but the DAC also has to sync to the converter.

 

If you have a PCI or PCIe card with a S/PDIF output, the important clock is on THAT board. This clock is used to send out the S/PDIF stream, and it is used to regulate how fast the board grabs data from the computer over the PCI or PCIe bus.

 

So whatever is sending out the S/PDIF stream is controlling the "clocking" of the ssystem.

 

There are some exceptions to this, many "pro" devices have a "word clock input" which synchronizes the output to an external clock source, primarily used because studios frequently have multiple boxes, it makes a lot of sense in this case to synch all of them to one external clock rather than each one trying to sync to another one.

 

John S.

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Maldur   

USB - copper lines with ground

LAN - copper lines with ground

 

This is true for USB, but not for LAN, because data goes through line transformators in both sides- basically the lines are galvanically isolated.

Ground connection is possible only with grounded/shielded cables, mainly used in outdoor application (there grounded shield is needed because danger of lightning).

Ordinary LAN cables for indoor use don't have any shield - thats why ground connection is not possible.

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In an S/PDIF system (in any of its flavors) the source is in charge of the clocking.

...

So whatever is sending out the S/PDIF stream is controlling the "clocking" of the ssystem.

 

John S.

 

Is this true for the ESS Sabre DAC? My understanding from the WP on this chip is that it dumps the S/PDIF interleaved clock data completely and uses a separate downstream mechanism for timing the L/R channel data.

 

(See: http://www.esstech.com/PDF/sabrewp.pdf)

 

I use Toslink as the connection between my transport and my EE (Sabre) DAC - primarily for galvanic isolation - and the results are really, really good ... possibly due to this jitter correction technique.

 

Ref. the Ethernet comments elsewhere: Ethernet is a 'reliable' protocol, like TCP/IP, so occurrences of 'bad' data being transmitted should be pretty rare. And even if some PCM data were sent 'bad' or 'corrupted', it would surely exhibit itself in the form of clicks or pops.

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This is true for USB, but not for LAN, because data goes through line transformators in both sides- basically the lines are galvanically isolated.

Ground connection is possible only with grounded/shielded cables, mainly used in outdoor application (there grounded shield is needed because danger of lightning).

Ordinary LAN cables for indoor use don't have any shield - thats why ground connection is not possible.

 

Just to expand a little more with Ethernet connections, there is an isolation transformer built into every NIC, yes so a ground connection is not required and would cause more pain. The system is a true differential like an XLR if you like.

 

Now that is not available with USB, so the DAC needs to make its own "isolation", by other techniques, buffering, and locally re-clocking, then the issue is gone anyway.

 

Usually a shielded Ethernet cable has a limit of 70m whereas unshielded is 100m. The problem with Ethernet is getting the protocol conversion from TCP/IP to USB2, PS Audio failed with the Bridge, Sotm got it right with the 100-s (check the front page of CA, review is there).

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