Quality of the digital data output from a CD player/transport

[shanmune]

When some say that the CD transport is one of the most important components in an audio system chain, I used to think it was a myth. I used to wonder how a digital data output from two different CD players/transports can vary when playing a same CD. Later, I used to hear the word "jitter", but I didn't understand what it is all about it and I don't know if that was my ignorance on my part. Then, I came to read this article which gives a very simple and basic understanding about what jitter is. Though I am a noob, the article was easy to follow.

Digital Interfaces - An Introduction - Part 1.1 [English]

The above article is divided into 5 parts. The first three parts are very interesting to read and part#3 gives a very simple explanation about jitter in the digital-audio world.

 

[jagdish_p]

Good article

The author classifies the digital interconnect in the following order. Highest quality first. ( jitter effect)

1) SPDIF
2) Toslink
3) USB - not well researched

I was under the impression that an asynchronous USB provides the best quality.
What is the experience of other FM s

 

[koushik]

I have the similar experience with digital connectivity.
SPDIF > OPTICAL > USB.

But there is a catch. USB will eventually be converted internally to similar stream as SPDIF. So, it is the implementation that matters. A good USB to SPDIF converter can make a big difference. But most of the USB DAC, and also DAC with USB connectivity for that matter, is poorly implemented.

Optical connectivity has limited bandwith. So although it provides good isolations from electrical interference and is not great for music as spdif.

 

[shanmune]

How do we rate HDMI (purely on the grounds of digital audio transfer) against SPDIF > OPTICAL > USB ?
I know there are no audio ONLY components which use HDMI, but your thoughts on audio transfer ????

 

[koushik]

How do we rate HDMI (purely on the grounds of digital audio transfer) against SPDIF > OPTICAL > USB ?
I know there are no audio ONLY components which use HDMI, but your thoughts on audio transfer ????

No idea ... I never had any enough revealing system with HDMI connectivity to compare them.
My AVR does have 3 of them (HDMI, SPDIF and Optical) but I don't think any test using a basic AVR will reveal anything like this.
And unfortunately, I don't know any good DAC with HDMI.

 

[IndianEars]

My 2 cents ....

HDMI is only a connector. Its usually used for I2S.

I2S is the Native interface for most DAC, but cable lengths are restricted to approx 50 cms which is not very practical.

I2S is the best possible interface. Period.

This is because i2S has separate wires for Data and the Clock.



All other interfaces are a HUGE Compromise compared to I2S.




The SPDIF has only 2 wires. There is no Clock.... The Clock signal is Inferred ( guessed LOL ). Its the the most universally used External interface.



TOSLINK ( Toshiba Sony ) takes the SPDIF, converts it to light for transmission and adds a Light to electricity converter at the receiving end.

Adding 2 electrical / optical interfaces cant do good,.

Further, TOSLINK has been optimised for mass market ( low cost) and mass production, not for the highest techical performance.




USB sends the data as packets rather than a stream. A cursory tech review will show USB as the worst, but its not so bad.

A LOT of work has gone into USB implemention for Audio applications, including Async USB.

Much Like Nakamichi elevated the dictation cassette into a serious Hi Fi medium, some USB implementations are Excellent...

 

[IndianEars]

I forgot to add, on my Chord QBD 76HDSD DAC, the USB fed from a Win PC sounds better than when fed SPDIF (Sony Philips Digital Interface) from my CD Player which uses an excellent Philips CD Pro transport.

 

[anuragn]

My 2 cents ....

HDMI is only a connector. Its usually used for I2S.

I2S is the Native interface for most DAC, but cable lengths are restricted to approx 50 cms which is not very practical.

I2S is the best possible interface. Period.

This is because i2S has separate wires for Data and the Clock.

If HDMI uses i2S, then how come we see HDMI cables several metres long?

 

[Nikhil]

Current implementation of HDMI is mainly for video applications (movies).
Audio via HDMI has massive jitter as far as I know at the moment.

In my DAC, the SPDIF and Toslink are limited to 24/96k Hz
The Async USB goes upto 24/192k Hz and is the way to higher resolution files.

 

[Santy]

IS transfer protocol is different from the mainstream audio/video application of HDMI connectors/ cables. DAC with IS will not work with standard HDMI output of our media players.

This is an FAQ answered by Wyred 4 sound (the DAC-2 and above have IS input)

Can I plug a regular HDMI output into the DAC-2 IS input and stream data?

The DAC-2 I2S input is specifically for a balanced IS signal and will not work with standard HDMI outputs that you will find on electronics such as some TVs, Audio Video Receivers, DVD players, etc. even though they will plug into it. The reason for choosing the HDMI style plug and cable is that it can stream high speed with very little signal degradation and it is simply a great cable design. IS is beneficial when streaming audio because it carries all of the clocking information and data on separate lines of code rendering it jitter free.

 

[thx911]

DAC with IS will not work with standard HDMI output of our media players

Santy, would you know if this is applicable for DSD bitstreaming aswell?

Thanks

 

[Santy]

Santy, would you know if this is applicable for DSD bitstreaming aswell?

Devices that accept DSD over HDMI, are on standard protocol and not IS. I am not sure if IS protocol supports DSD streaming (quite possibly it can). But IS is not common for inter-device connection as it is made primarily for connections between ICs within a device.

From Wiki

I2S, also known as Inter-IC Sound is an electrical serial bus interface standard used for connecting digital audio devices together. It is used to communicate PCM audio data between integrated circuits in an electronic device

 

[jls001]

If HDMI uses i2S, then how come we see HDMI cables several metres long?

The I2S signal will be encoded to HDMI protocol. So the signal will now carry as far as HDMI will go.