• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Study: Is I²S interface better for DACs than S/PDIF or USB?

DonH56

Master Contributor
Technical Expert
Forum Donor
Joined
Mar 15, 2016
Messages
7,834
Likes
16,496
Location
Monument, CO
Generally speaking, having an independent clock source introduces a number of issues. You now have two independent jitter sources so jitter is usually higher, it takes additional power and cost to drive two signals instead of one, and now synchronization and skew between clock and data lines is critical. Systems using independent clock signals tend to be low-rate and low-power applications where the signal can be a constant value for a "long" time like I2C. Then skew can be fairly large and still allow plenty of margin to capture the data, and there is no worry about a PLL free-running long enough to rail the oscillator or whatever. Simple hand shaking is enough to start acquisition and recover the bits. Signals like the data streams in networks and PCs are not normally set to a constant (static, DC) value except in power-down conditions; otherwise, an idle signal is still toggling but sending random ("nonsense") data so the clock and data recovery (CDR) circuits stay locked to the signal. And during normal operation encoding is used to "scramble" the data and make sure the bit stream is "busy"; that is, the run length of 1's and 0's is limited by design so there are never too many in a row, and the CDR circuit always has plenty of bit transitions to keep it happy (stay in synch).

Some RF systems, and probably others, use a dedicated LO ("clock") signal that is carefully buffered and distributed, often to multiple end points (e.g. phased-array radars). That is a far different application than sending bits around in an audio or computer system (typically point-to-point links rather than distributed systems).

FWIWFM - Don
 

Zog

Active Member
Joined
Mar 13, 2019
Messages
255
Likes
290
This is an analysis of I²S interface to see if it is superior to S/PDIF or USB interconnects for audio DACs.
If I understand correctly, what you have tested is a three box paradigm. There is a Source or Transport. Then there is the Singxer device. Then there is the DAC. So what is happening here is that the Singxer box has been interpolated - the transport is still outputting via spdif or USB.

It seems to me that a more meaningful comparison would be if the Source output I2S and the DAC received that - two boxes only. I think this is what Paul McGowan was on about. I suppose the PS audio Transport(s) have the facility to do that. If using a PC as a Source then there is the possibility of using a 'soundcard' that transmits via I2S. In that way exporting via spdif / usb / AES can be avoided.

Is there such an item? The company known as Pink Faun make such a thing, among others. They call their product an Audio Bridge. They are at
Pink Faun
I use this from a PC into the I2S connection of my Wyred4Sound DAC, using HDMI cable. (The same DAC that you recently reviewed).
What I would be very interested in is a comparison between:
(a) The W4S (or any) DAC via USB and/or spdif; and
(b) The W4S (or any) DAC via I2S - where the I2S connection came from the source.

Thank you very much for these reviews. I find them enlightening and if you ever got the chance to do further work on I2S I would be very interested.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,381
Location
Seattle Area
If I understand correctly, what you have tested is a three box paradigm. There is a Source or Transport. Then there is the Singxer device. Then there is the DAC. So what is happening here is that the Singxer box has been interpolated - the transport is still outputting via spdif or USB.
No, that is not the case. The "transport" is the computer with only one connection to Singxer SU-1: USB. The Singxer then simultaneously outputs S/PDIF and IIS to the best of its ability. The DAC receives the same and generates analog output.

This is the choice users have: either use USB to S/PDIF or USB to IIS. No computer source by itself has IIS.

It seems to me that a more meaningful comparison would be if the Source output I2S and the DAC received that - two boxes only.
That is what the Singxer X-1 is doing. It is the source as far as the DAC is concerned. Digital data is bit-perfect so the only thing that is different, is the electrical connection and protocol to transmit the bits.
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,381
Location
Seattle Area
(a) The W4S (or any) DAC via USB and/or spdif; and
(b) The W4S (or any) DAC via I2S - where the I2S connection came from the source.
This is there for DAC-X26. The dashboard view in the review shows it from USB, and what is there, for both IIS and S/PDIF.
 

Zog

Active Member
Joined
Mar 13, 2019
Messages
255
Likes
290
This is the choice users have: either use USB to S/PDIF or USB to IIS. No computer source by itself has IIS.
Not with the Pink Faun. It is actually impossible to have USB. Their Audio Bridge card is a PCI card that outputs I2S. No USB in sight. This is why it is a two box solution. One could argue that the card is effectively a separate item but the point is that there is only one line between the PC and the DAC, as there is in a CD player between the transport and its internal DAC. With the Singxer we have USB (input) and I2S (output). With the Pink Faun it is only I2S.

The theoretical objection I have with the Singxer is that it is functionally irrelevant. I understand the DAC will convert the USB (or spdif) to I2S. So why not let the DAC do that rather than a third box. I guess if the third box does a better job then that is a practical solution.
 
  • Like
Reactions: jjk

A-Shah

Member
Joined
Feb 7, 2019
Messages
8
Likes
1
Amir !
thanks I am very fond of Paul's Video they do add to the little knowledge I have , Unfortunately the I2S has always bugged me on PS audio DirectStream DAC as I cannot use it with my HDMi OPPO 205 without some external hardware so I am stuck using a SPIDF /Coaxial, I did try a heed CD player once with the DAC it seemed to have sounded more dynamic, but that could just have been psychological
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,381
Location
Seattle Area
My pleasure. I am glad you found it useful. I was going through my old gear and I found another USB to IIS box (SMSL?). So maybe I take another shot at this in the future.
 

jjk

Active Member
Forum Donor
Joined
Oct 18, 2019
Messages
139
Likes
110
Location
San Antonio, TX
Not with the Pink Faun. It is actually impossible to have USB. Their Audio Bridge card is a PCI card that outputs I2S. No USB in sight. This is why it is a two box solution. One could argue that the card is effectively a separate item but the point is that there is only one line between the PC and the DAC, as there is in a CD player between the transport and its internal DAC. With the Singxer we have USB (input) and I2S (output). With the Pink Faun it is only I2S.

The theoretical objection I have with the Singxer is that it is functionally irrelevant. I understand the DAC will convert the USB (or spdif) to I2S. So why not let the DAC do that rather than a third box. I guess if the third box does a better job then that is a practical solution.


I too have the PinkFaun streamer with the I2S bridge. Mine is the 8 channel version; I employ 3 dacs. Considering adding a 4th to support subs 2 and 3 through JRiver (kind of like minidsp).
I believe in it although it would be cool to see the measurements.
Good luck to either of us sending the streamer (beast) in to Amir for measurements!:D
 

Arvind

Active Member
Joined
Nov 9, 2018
Messages
106
Likes
76
Location
New Delhi, India
I2S input on my Sabaj D5 is the only way to listen SACDs played on my Sony UBX 800M2. HDMI ARC outputs to a HDMI to I2S converter which outputs DSD over I2S to Sabaj D5 via HDMI connector.
Screenshot_2019-10-24-09-51-21-16_57e717c094f371a1dada6567a1123b99.png
 

Jimster480

Major Contributor
Joined
Jan 26, 2018
Messages
2,880
Likes
2,032
Location
Tampa Bay
I2S input on my Sabaj D5 is the only way to listen SACDs played on my Sony UBX 800M2. HDMI ARC outputs to a HDMI to I2S converter which outputs DSD over I2S to Sabaj D5 via HDMI connector.View attachment 36803
I wonder if there is a performance penalty for doing it like this...
I also didn't know that there were SACD's anymore or that there were any modern players that could play them.
 

miero

Active Member
Joined
Aug 1, 2018
Messages
241
Likes
289
I2S input on my Sabaj D5 is the only way to listen SACDs played on my Sony UBX 800M2. HDMI ARC outputs to a HDMI to I2S converter which outputs DSD over I2S to Sabaj D5 via HDMI connector.View attachment 36803
SACD over HDMI? I guess it is not streamed as DSD but PCM...

EDIT: It seems to be possible
HDMI 1.2 include: Support for One Bit Audio format, such as Super Audio CD's DSD (Direct Stream Digital)
Source: https://denon.custhelp.com/app/answers/detail/a_id/192/~/differences-between-hdmi-versions-1.1,-1.2,-1.3a,-1.4-and-2.0?
 
Last edited:
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,368
Likes
234,381
Location
Seattle Area
SACD over HDMI? I guess it is not streamed as DSD but PCM...

EDIT: It seems to be possible
Yes, that was put in long time ago.
 

jjk

Active Member
Forum Donor
Joined
Oct 18, 2019
Messages
139
Likes
110
Location
San Antonio, TX
If interested in I2S, take a look at pinkfaun.com. It's a Dutch company.
These guys know what they're doing.
 

garbulky

Major Contributor
Joined
Feb 14, 2018
Messages
1,510
Likes
827
This is not a native i2s source though. It’s a usb to i2s. The audio goes through usb first. So people can say the measurements can’t be any better than the usb converter. It may be impossible to find but don’t you have native i2s sources? Some motherboards have them.
 

Veri

Master Contributor
Joined
Feb 6, 2018
Messages
9,596
Likes
12,036
This is not a native i2s source though. It’s a usb to i2s. The audio goes through usb first. So people can say the measurements can’t be any better than the usb converter. It may be impossible to find but don’t you have native i2s sources? Some motherboards have them.
Well you need to interface on something, right...
 

mkawa

Addicted to Fun and Learning
Joined
Sep 17, 2019
Messages
788
Likes
695
the raspi soc has an i2s feed that comes directly from the soc. other media processors do as well. that's the only situation where i can see this as being a reasonable alternative to PCM.
 

Zog

Active Member
Joined
Mar 13, 2019
Messages
255
Likes
290
This is not a native i2s source though. It’s a usb to i2s. The audio goes through usb first. So people can say the measurements can’t be any better than the usb converter. It may be impossible to find but don’t you have native i2s sources? Some motherboards have them.
My understanding is that it is a native I2S source. The Pink Faun Audio Bridge that I have is here . There is no USB in sight. It operates like any soundcard and goes direct to the DAC. That is, providing the DAC has an I2S input. This latter point is a little tricky as there is no standardised pin alignment. However Pink Faun will be accommodating in ensuring that their output and your input will match.
 
Top Bottom