Digital Facts and realities?

[Jimbo]

Jitter and Timing destroy many aspects of digital audio including bass, soundstage and can smear the audio image. When they are addressed as best as possible you can hear the improvements but you need to start with bit perfect ripped files first. CD is not going to be even in the starting blocks and will never give the best representation that can be delivered by digital audio.

Until you investigate this route Martin, you will just assume that what you have is perfectly OK which is fair enough. But considering you are a committed digital based audiophile you owe it to yourself to at least try it in your own system.

You heard Olivers Pi3 BOSS set up and I noticed you did not mention this in your post on the new speaker cables. I would be surprised if you were not impressed by what you heard from this £200 set up!

Go on give it a go and see what you are missing!

[Macca]

Jitter and Timing destroy many aspects of digital audio including bass, soundstage and can smear the audio image. When they are addressed as best as possible you can hear the improvements but you need to start with bit perfect ripped files first. CD is not going to be even in the starting blocks and will never give the best representation that can be delivered by digital audio.

Until you investigate this route Martin, you will just assume that what you have is perfectly OK which is fair enough. But considering you are a committed digital based audiophile you owe it to yourself to at least try it in your own system.

You heard Olivers Pi3 BOSS set up and I noticed you did not mention this in your post on the new speaker cables. I would be surprised if you were not impressed by what you heard from this £200 set up!

Go on give it a go and see what you are missing!

What you are describing about the audible effect of jitter is incorrect. And as the AES paper I linked to demonstrates, jitter is inaudible in all but worst case scenarios. All cd players deal satisfactorily with jitter. You are more actually likely to increase jitter by using a separate transport/streamer and DAC, not less likely. Although it still won't matter. And bit perfect is irrelevant, it makes no difference if you read the file from a cd or from a hard drive So we are at pretty much 180 degree opposing views


Not that it matters, I think it is good that all sides of the picture get discussed.


Ollies Pi set up sounded good. £200 is indeed a bargain. I'd have to listen to it in my system though before I could safely say it is an improvement on the Sony cd player I'm using right now which was an even better bargain at £50.

Ollie's pie set up sounds good because he has properly sorted amplification. That's why when we stuck a budget 1995 Sony CD player (£40 from ebay) in there last Autumn it also sounded good.

[Jimbo]

What you are describing about the audible effect of jitter is incorrect. And as the AES paper I linked to demonstrates, jitter is inaudible in all but worst case scenarios. All cd players deal satisfactorily with jitter. You are more actually likely to increase jitter by using a separate transport/streamer and DAC, not less likely. Although it still won't matter. And bit perfect is irrelevant, it makes no difference if you read the file from a cd or from a hard drive So we are at pretty much 180 degree opposing views


Not that it matters, I think it is good that all sides of the picture get discussed.


Ollies Pi set up sounded good. £200 is indeed a bargain. I'd have to listen to it in my system though before I could safely say it is an improvement on the Sony cd player I'm using right now which was an even better bargain at £50.

Ollie's pie set up sounds good because he has properly sorted amplification. That's why when we stuck a budget 1995 Sony CD player (£40 from ebay) in there last Autumn it also sounded good.

I think we will have to just disagree about quite a few of your comments on digital. I think they are all wrong but good for discussion as you say.

I would be interested in what you thought of the Pi in your system as it sorts many of the aspects that undermine digital and as a result it presents a superb digital sound. It is because of the lack of jitter, bit perfect files, well sorted PSU and excellent clock timing that it sounds so good, however this would be at odds with your theories.

In the end it is how it sounds that matters and for me it is approaching analogue very closely especially on some material.

That is a very high recommendation in my book as I am obviously a vinylista!

[Light Dependant Resistor]

Jitter was a solved problem before CD even came out. I've got vintage players here that will demonstrate that on a practical level. (Marantz CD54 from 1984, Technics SLP1200 from 1989).

The SQ issues people experience with CD have nothing to do with jitter.

Martin politely suggest you have a read of this study published in October of 1993 https://www.stereophile.com/referenc...ter/index.html
Although some DAC integrated circuits have improved such as those from Crystal used in a lot of CD players NAD Marantz to name two, the
fundamentals of addressing jitter outlined by Reme Fourre and also study done in the UK by Malcolm Hawksford https://www.youtube.com/watch?v=b5nzFejc2KA
remains elusive to most commercially available equipment.

In Malcolms talk the frequency response of digital is raised as i have pointed out already a number of times at 6 mins into the you tube video, is discussed as being inadequate or compromised
and Malcolm suggests 96 khz , inferring a audio frequency response to at least 45 khz allowing for some filtering before the Shannon/Nyquist point is reached.

[Gazjam]

I put it to you Sir that you are a Propellerhead.

What you are describing about the audible effect of jitter is incorrect. And as the AES paper I linked to demonstrates, jitter is inaudible in all but worst case scenarios. All cd players deal satisfactorily with jitter. You are more actually likely to increase jitter by using a separate transport/streamer and DAC, not less likely. Although it still won't matter. And bit perfect is irrelevant, it makes no difference if you read the file from a cd or from a hard drive So we are at pretty much 180 degree opposing views


Not that it matters, I think it is good that all sides of the picture get discussed.


Ollies Pi set up sounded good. £200 is indeed a bargain. I'd have to listen to it in my system though before I could safely say it is an improvement on the Sony cd player I'm using right now which was an even better bargain at £50.

Ollie's pie set up sounds good because he has properly sorted amplification. That's why when we stuck a budget 1995 Sony CD player (£40 from ebay) in there last Autumn it also sounded good.

[Macca]

Martin politely suggest you have a read of this study published in October of 1993 https://www.stereophile.com/referenc...ter/index.html
Although some DAC integrated circuits have improved such as those from Crystal used in a lot of CD players NAD Marantz to name two, the
fundamentals of addressing jitter outlined by Reme Fourre

.

It's an explanation of jitter and how to test for it. I'm not saying jitter does not exist.

Note in the article there is no mention of what jitter sounds like and what levels it has to be at before you can hear it. It's just taken as read from the opening of the article - 'Until recently, all problems in digital audio systems...' - that there are problems with the sound of digital audio and we need to look for them and solve them. No mention of how they manifest themselves, something which you would have thought might be slightly pertinent. Why do you suppose that was omitted?

[blackmetalboon]

It's an explanation of jitter and how to test for it. I'm not saying jitter does not exist.

Note in the article there is no mention of what jitter sounds like and what levels it has to be at before you can hear it. It's just taken as read from the opening of the article - 'Until recently, all problems in digital audio systems...' - that there are problems with the sound of digital audio and we need to look for them and solve them. No mention of how they manifest themselves, something which you would have thought might be slightly pertinent. Why do you suppose that was omitted?

Very good points/questions, Martin. I’m with you on this subject, a non-problem looking for a solution. I know I may be unpopular for this view, but how many people who have this problems with the digital reproduction of music come from the analogue generation? When people have commented on my (digital) system as being very analogue sounding, I’ve not seen it as a compliment.

[Light Dependant Resistor]

It's an explanation of jitter and how to test for it. I'm not saying jitter does not exist.

Note in the article there is no mention of what jitter sounds like and what levels it has to be at before you can hear it. It's just taken as read from the opening of the article - 'Until recently, all problems in digital audio systems...' - that there are problems with the sound of digital audio and we need to look for them and solve them. No mention of how they manifest themselves, something which you would have thought might be slightly pertinent. Why do you suppose that was omitted?

On page 2 of the Reme Fourre article, a figure of 200 pico seconds jitter error is used to describe spurious tones that then appear at higher harmonics. Complicating is as the dynamic range
increases with higher bit D/A converters the problems of jitter just get worse. Malcolm Hawksford begins discussion of the problems of jitter distortion at 14.30 into the You tube video
https://www.youtube.com/watch?v=b5nzFejc2KA

Jitter being a distortion displaces timing to no longer sound like the original recording.

Jitter is manifested in inability firstly of the Analog to Digital Conversion, to preserve time correctly, and secondly in Digital to Analog Conversion, but
mostly where a transport and outboard D/A are implemented, namely the SPDIF or AES/EBU interface as outlined by Reme Fourre on page 2
https://www.stereophile.com/content/...terface-page-2

"Jitter in the digital interface
A logical question to ask is: Where does this clock jitter originate? The main source of jitter is the digital interface between a digital source such as a CD transport and the D/A converter. This interface is either the AES/EBU (Audio Engineering Society/European Broadcast Union) or S/PDIF (Sony/Philips Digital Interface Format) format. With the exception of voltage levels and line impedances, the two formats are very similar. Both carry two channels of digital audio data (up to 24 bits per sample per channel, though only 16 are currently used in consumer applications), control bits, parity bits, and checksum bits. The bit rate is 64 times the sampling frequency (64Fs), and the baud rate (the rate at which the line may change state) is 128Fs. For the CD's 44.1kHz sampling rate, the S/PDIF or AES/EBU interface has a bit rate of 2,822,400 bits per second and a baud rate of 5.6448MHz.

Two optical-fiber interfaces are also in use: TosLink and ST-type, both of which carry information optically instead of electrically. The TosLink interface, more properly called "EIAJ optical," uses a plastic optical fiber. AT&T ST-type optical uses a glass optical fiber. These two optical formats are merely transmission methods; they both use the AES/EBU or S/PDIF data formats.

The digital interface has two major functions: It carries the digital data and it carries the sampling clock. Both data and clock are transmitted on the same physical electrical conductors or optical fiber link: data are encoded using a pulse-modulation scheme, and the clock is embedded in the pulse edges. This system requires that the clock and data be separated in the digital processor, a function performed by the digital processor's input receiver. The "recovered" clock then serves as the processor's master clock. Consequently, jitter in the interface data stream produces clock jitter at the DAC. This is the mechanism by which transports affect a digital system's sonic performance. Moreover, the quality of the digital interface implementation greatly affects the amount of jitter in the recovered clock.

Interface jitter is similar to the periodic clock jitter described earlier. Because current input receiver implementations detect signal edges by comparing the input voltage to zero, jitter in the digital interface signal is defined as the sequence of the timing errors on the voltage zero crossings.

As with noise, jitter has multiple causes. One of them is electrical noise picked up on the interface cable. Noise causes the zero crossing points to shift slightly—which is, by definition, interface jitter. If the digital interface signal has an average slope of 20V/µs (a typical value in many S/PDIF implementations), just 10mV RMS of noise, for example, will introduce 500ps RMS of jitter. '

I looked at this very issue to disable SPDIF and replace it with 3 discrete codes between a CD transport and a Audio Synethesis DSM in 1997 , described here: http://www.enjoythemusic.com/magazin...iesofspdif.htm

The benefits were improved bass response and stereo separation compared to SPDIF transfer that sounded muddled. I also did comparison with the best available turntable listening to each through Quad ESL63's
The source was a Three Blind Mice LP and identical Three Blind Mice CD - the benefit of the digital three code system was that it lacked any noise that the LP provided , but otherwise sounded
the same.

[Macca]

Very good points/questions, Martin. I’m with you on this subject, a non-problem looking for a solution. I know I may be unpopular for this view, but how many people who have this problems with the digital reproduction of music come from the analogue generation? When people have commented on my (digital) system as being very analogue sounding, I’ve not seen it as a compliment.

It is in fact the orthodox engineering view on the subject. The alternative point of view expressed by sites like HB project - that we can hear frequencies higher than 22Khz, that tiny amounts of jitter are audible, that pre and post ringing are audible, is not taken seriously.


A lot of research has been done over the past 100 years on what we are capable of hearing. Not from the perspective of hi-fi but as a general subject. When digital audio (CD) was being designed in the 1970s this already existing and accepted research was used to set the upper limit of frequency response at 22Khz. Since then nothing has changed as far as medical science is concerned. Someone mentioned bone conductance earlier in the thread. yes this does work - if the loudspeaker is up against your skull and the high frequencies are transmitted at sufficient levels (i.e high levels). None of this happens in reality.

[Light Dependant Resistor]

It is in fact the orthodox engineering view on the subject. The alternative point of view expressed by sites like HB project - that we can hear frequencies higher than 22Khz, that tiny amounts of jitter are audible, that pre and post ringing are audible, is not taken seriously.


A lot of research has been done over the past 100 years on what we are capable of hearing. Not from the perspective of hi-fi but as a general subject. When digital audio (CD) was being designed in the 1970s this already existing and accepted research was used to set the upper limit of frequency response at 22Khz. Since then nothing has changed as far as medical science is concerned. Someone mentioned bone conductance earlier in the thread. yes this does work - if the loudspeaker is up against your skull and the high frequencies are transmitted at sufficient levels (i.e high levels). None of this happens in reality.

What you are missing is that audio in the spectrum we hear is changed detrimentally, where frequency response is filtered. https://earthworksaudio.com/wp-conte...yond-20kHz.pdf
No there was no proper research done rather it was found a upper limit of 20- 22.05 Khz suited the redbook standard to provide a music CD disc of 74 mins duration, as always market product comes first rather
than quality.