Why does SPDIF basically suck?

[Ralf11]

and does it suck for Redbook, or only for high bit rates?

 

 

[Nordkapp]

Beats USB....Why do you think it sucks? Because of its bit and frequency limits?

[nbpf]

All sucks, not only SPDIF! Just keep all data on the DAC. Then, the only data transfer that has to take place is from disk into RAM. This can be optimized by the OS. The DAC does not even need to be connected to the LAN at replay time: once a selection has been made, it can disconnect.   

[mansr]

If it sucks, it is because the receiver is, one way or another, slaved to the transmitter clock. Synchronising to the incoming clock is difficult to do without introducing jitter.

[nbpf]

21 minutes ago, mansr said:

If it sucks, it is because the receiver is, one way or another, slaved to the transmitter clock. Synchronising to the incoming clock is difficult to do without introducing jitter.

True but this would not matter if the receiver had a (admittedly very) large buffer and would start replay only after the data transfer has completed. This would only work for LAN streaming, of course. But it would work!  

[mansr]

5 minutes ago, nbpf said:

True but this would not matter if the receiver had a (admittedly very) large buffer and would start replay only after the data transfer has completed. This would only work for LAN streaming, of course. But it would work!  

S/PDIF is synchronous. It sends the data at the rate it is meant to be played back. To buffer an entire album like this would take a very long time. Wagner's Götterdämmerung, for instance, is over 4 hours long.

[Melvin]

I'm surprised GUTB didn't start this thread.

[nbpf]

2 minutes ago, mansr said:

S/PDIF is synchronous. It sends the data at the rate it is meant to be played back. To buffer an entire album like this would take a very long time. Wagner's Götterdämmerung, for instance, is over 4 hours long.

Right, in this case S/PDIF really sucks! Still, one could transfer the files overnight and play them the day after. Finally, one does not typically embark in a Götterdämmerung impromptu! 

[sandyk]

Well implemented Coax SPDIF can sound markedly better than most USB implementations , although it's bandwidth is inadequate for recent DSD implementations, where there is a limited amount of material available, and not in popular music either.

There is no reason why Coax SPDIF's bandwidth couldn't be markedly improved these days if there was a will to do so.

[Fitzcaraldo215]

Depending on your point of view, they all suck - Spdif, Toslink, USB,  I2s, HDMI, Ethernet, etc. Or, they each require competent engineering to have any chance of success.  And, even on a best effort engineering basis, some approaches have inherent technological advantages over others.  

 

Also, different DACs have either limitations because they predate newer approaches, like legacy DACs, or they may favor one interconnection protocol approach over others in their design and engineering philosophy.  

 

While in other things older may sometimes be better, in digital technology I know of no case over time where that was ever true on a sustained, market tested basis.  Alternatively, brand new approaches may not necessarily be better just because they are newer.  There are sometimes false starts that fail to muster over the longer term, even in spite of seeming technical advantages in some areas.

 

To me, good old spdif and its related AES/EBU or Toslink protocols are all ancient legacy methods.  They are limited in bandwidth and channel count, and they are obviously not the way of the future.  I don't see any technical advantages at all.  

 

I think that currently, USB 2.0, if competently engineered,  is perfectly capable of delivering audio as good as it gets, without fancy cables or add on gizmos.

 

 

 

 

[sandyk]

11 minutes ago, Fitzcaraldo215 said:

I think that currently, USB 2.0, if competently engineered,  is perfectly capable of delivering audio as good as it gets, without fancy cables or add on gizmos.

 

 

A vast amount of feedback in other areas of the forum suggests that this has yet to be achieved.

[Ralf11]

1 hour ago, mansr said:

If it sucks, it is because the receiver is, one way or another, slaved to the transmitter clock. Synchronising to the incoming clock is difficult to do without introducing jitter.

 

ah - so that's why people mention SPDIF jitter...

 

it does solve the galvanic isolation problem of USB

 

Nord - I started this based on some comments from barrows in another thread (so as not to derail that thread) - 'basically sucks' are his words

[mansr]

8 minutes ago, Ralf11 said:

ah - so that's why people mention SPDIF jitter...

 

it does solve the galvanic isolation problem of USB

In the Toslink incarnation, yes.

[One and a half]

17 minutes ago, sandyk said:

Well implemented Coax SPDIF can sound markedly better than most USB implementations , although it's bandwidth is inadequate for recent DSD implementations, where there is a limited amount of material available, and not in popular music either.

There is no reason why Coax SPDIF's bandwidth couldn't be markedly improved these days if there was a will to do so.

Don’t forget the large offering of SACD that can now be ripped and played back on computer players. 

Some of this music is now regretfully out of print.

 

I like AES3 oddly enough,  as you mention about well implemented coax, last night compared a red book playback to USB on the same DAC A/B via Roon, simple to do, USB had a distinct edge in resolution, not much, but enough to not engage interest.

 

The same music when played on a CD player wiped both computer playback systems (again), no contest.

 

The album was Lydian Collective ‘Adventure’.

[One and a half]

22 minutes ago, sandyk said:

 

A vast amount of feedback in other areas of the forum suggests that this has yet to be achieved.

Just as with S/PDIF...no digital audio transmission could ever until a major rethink about timing is accepted.

[Pete-FIN]

41 minutes ago, sandyk said:

Well implemented Coax SPDIF can sound markedly better than most USB implementations...

When compared witch one sounds better, well implemented Coax SPDIF or well implemented USB? I am in the impression that well implemented USB would be better.

 

EDIT ... when listening PCM music files.

[Fitzcaraldo215]

14 minutes ago, sandyk said:

 

A vast amount of feedback in other areas of the forum suggests that this has yet to be achieved.

Which proves what, exactly? Which DACs were they using?  I feel their, as well as your own, pain in not getting maximum enjoyment from simple asynch USB, with the right DAC, of course.  I do, pure and simple.  Why should I care what you or they think?

 

Will audiophiles ever agree on anything as a result of sighted listening?  

[Fitzcaraldo215]

7 minutes ago, One and a half said:

Just as with S/PDIF...no digital audio transmission could ever until a major rethink about timing is accepted.

What could possibly be better than total control of the totally buffered d-a process by the DAC master clock?  Oh, wait.  Spdif/Toslink/AESEBU do not do that.  Asych USB does.  Hmmm.

[One and a half]

11 minutes ago, Fitzcaraldo215 said:

What could possibly be better than total control of the totally buffered d-a process by the DAC master clock?  Oh, wait.  Spdif/Toslink/AESEBU do not do that.  Asych USB does.  Hmmm.

A buffer certainly helps too.

[mansr]

3 minutes ago, One and a half said:

A buffer certainly helps too.

Every digital audio playback device ever made has some form of buffer.

[Superdad]

Uh, I think the obvious is being overlooked here:

 

Forget the DAC for a moment.  If the source is a computer (or some form thereof) playing back files (ripped from CD, downloaded, streamed, whatever), then that data has to exit the computer in some format.  While I know there are some music servers with S/PDIF output--and some sound cards with the same--a computer is a nasty environment within which to place audio clocks and S/PDIF transmitting parts.

 

So the vast majority of "computer audiophiles" are sending the data from their computers towards their DACs either via USB or Ethernet.  And at some point--generally in the DAC--that data will go through PHY chips/processor and a protocol engine and be turned into I2S/DSD for the actual DAC chips/ladders, whatever.

 

Thus use of S/PDIF or AES EBU inputs on a DAC generally requires the use of a DDC, most of which take the form of a USB>S/PDIF converter.  While of course quality of implementation is the key, think about the general data flow.  

That is, which is the better path?:

a) Computer USB>  USB input of DDC > S/PDIF transmitter (embedding clock in data) > S/PDIF cable > DAC's S/PDIF receiver chip> reclocking > I2S for the DAC section.  

OR

b) Computer USB> USB input of DAC > I2S to the DAC section.

And an Ethernet-input DAC is about equivalent: Ethernet PHY/processor > I2S

 

Any DAC manufacturer who still says their S/PDIF input is better than their own USB input is simply admitting that they can't design a decent USB or Ethernet input board (or they want to sell their own outboard DDC).

 

Just my $0.02  

[sandyk]

1 hour ago, Pete-FIN said:

When compared witch one sounds better, well implemented Coax SPDIF or well implemented USB? I am in the impression that well implemented USB would be better.

 

EDIT ... when listening PCM music files.

 

The only way to get well implemented USB to outperform well implemented Coax SPDIF , is to remove the degrading influence of the PC's internal +5V SMPS, and replace it with clean low noise power via preferably an external battery derived +5V supply, which has no capacitive effects back to A.C. mains earth, and use a higher quality USB cable of the shortest possible length ,where there is vastly improved isolation between the D+ and D- leads and the incoming power leads.

 Well implemented Coax SPDIF assumes the use of the correct 75 ohms BNC plugs and sockets, as well as quality isolation transformers at both ends .

BTW, the best USB cable is NO USB cable, just a modified USB-A male to USB-A  female adaptor .

 It is also possible for USB memory sticks powered via a  clean external supply to work with a modified USB adaptor where +5V and screen are not connected through. This helps to remove possible earth loops with desktop PCs as the 0 volts and screen of USB memory sticks are internally connected together, and the PC's internal 0 volts is connected to mains earth.

 In this case I use a USB Regen, but I need to insert the USB memory stick into the Regen AFTER the adaptor is plugged in and the PSU is turned on , in order for the USB memory stick to be recognised by Windows 10.

 In the attached photo, the bottom cable is replaced by the adaptor.

[sandyk]

2 hours ago, Fitzcaraldo215 said:

Why should I care what you or they think?

 

 Likewise !

[sandyk]

2 hours ago, Fitzcaraldo215 said:

What could possibly be better than total control of the totally buffered d-a process by the DAC master clock?

 

Improving the Signal Integrity BEFORE it is exported!

 

GI = GO

[Ralf11]

does it matter what noise is Behind the Digital Curtain as long as you isolate it?