[Tinker]

Dear Tinker and others,

Could you please explain the difference between "standard" audio cable (RCA to RCA), Video 75 ohm interconnect cable (RCA to RCA), and digital cable to me?  Is it 75 ohm per metre or per mile, a maximum of 75 ohm, a minimum of 75 ohm?

If there is a dispoal bin of "high quality, name brand" VIDEO cables looking nice and sleek with colourful covers and gold and satin connectors , would these work as satisfactorily, better or worse than AUDIO cable for an AUDIO interconnect applic ...

75 Ohms refers to the characteristic impedence of the cable (L/C ratio), and is independent of length (except for the fact that a real long cable will be dominated by resistance, which at a few ohms a mile will be quite a long cable!). The matching of characteristic impendences reduces ringing in digital circuits. These kinds of problems just don't come up in audio cables: the signals are neither fast enough nor the cables long enough for this to happen. There are a number of good 75Ohm cables. Belden, Monster and DHLabs al make hi-end ones, although I'm not going to recommend one.  There are undoubtedly some bargin bin DIY cables to be made too. I might do a post on this later.

Cheers,
        T.

[MarinRider]

Aspen's credibiity remains fully intact with the news that non-oversampling has been rejected for the DAKSA.

Having just borrowed a (12 year old) Cambridge Audio CD2 which uses 4 X TDA1541 interleaved to give 16 times oversampling, I am further convinced NONOS is nonsense.

[dayneger]

This is definitely one of the more interesting threads I've read in a long time!

That was very fast work on the AKSenter, or whatever you're calling the new center speaker.  What's different about it that makes it act like a point source, as compared to a "regular" speaker?

Question about the DAKSA: is it $US800 and $950 for all three stages, or just the first?  And is the kit fairly all-inclusive?

I must say, I'm tickled pink at the concept of near indepence from the transport quality.  For some reason I've always been rather loath to invest much money in that particular direction.

Keep up the great work!

Dayne

[DSK]

I must say, I'm tickled pink at the concept of near indepence from the transport quality.  Fo ...

This appears to be a lofty and very challenging goal. Many have trodden this path and implemented various circuits that were claimed to (nearly) eliminate differences between transports and digital cables. However, many who used these DACs claimed that the transport was still *at least* as important to the sound as the DAC, and that differences between digital cables could still be heard.

If Ben and Hugh can achieve this holy grail, in a DAC that outperforms its more expensive brethren, it will be a very significant product....enabling better quality sound to be achieved from a DAC/transport/cable combo, for less $$$, than has previously been possible....and I'm all for that!    

PS. I'm not casting doubt over whether the AKSA boys can do it, I'm just suggesting that it is more difficult than many seem to realise.

[AKSA]

Darren,

We know it's difficult - but can you see that determination is de rigeur for a retired Army Officer and a gifted academic with an engineering background?

Besides, it's fun, and as some Gallic wit once put it, 'Progress depends on the resolve of unreasonable men'.

Pricing on the DAKSA will be around $US600, $US850 and $US950 but is not set in stone until the inventory is in place.  It ain't cheap, but it will hopefully be the best DAC kit in the market.  That's the goal, anyway!

Cheers,

Hugh

[kyrill]

Ben and I have been burning the midnight oil.  

Two weeks ago Ben had completed the initial chipset and topology.  He has continued with refinement however and only three days ago he explained the finer points of the DAKSA's digital processing in a very pleasant cafe in the eastern suburbs of Melbourne.  . . . This will be incorporated onto a single pcb for the entire DAC, and DIYers should have no difficulty assembling the DAKSA.

I should caution anyone expecting this to be ready by Xmas. This is extremely unlikely; for starters several thousand dollars of sourcing is yet to come, not to mention thorough documentation, which can take up to three months. Needless to say, no deadlines will be given. ...

Time of above information: 05 oct 2003

Time of today: nearing may 2004

Any news when we can expect the DAKSA, Ben?  Hugh?

Shall I come over and help you write the manual ?

[Larry]

However, many who used these DACs claimed that the transport was still *at least* as important to the sound as the DAC, and that differences between digital cables could still be heard.

Theoretically, no matter what one has done to the DAC, the impact of the transport on the sound will still exist. What one can do on the DAC is to minimize the impact of interfacing between the transport and DAC including impedance mismatch, clock synchronization (jitter) and mutual interferences etc. It's possible to design a DAC to minimize the impact of the clock jitter, which may improve the sound,  while it's impossible to design a DAC to make the sound independant on the transport quality. The impact of the transport on the sound can only be improved by improving the transport, logically speaking. There are many more areas in the transport than the jitter that impact on the sound.

[kyrill]

Theoretically, no matter what one has done to the DAC, the impact of the transport on the sound will still exist. ;. . . . .  It's possible to design a DAC to minimize the impact of the clock jitter, which may improve the sound,  while it's impossible to design a DAC to make the sound independant on the transport quality. The impact  the transport on the sound can only be improved by improving the transport, logically speaking. There are many more areas in the transport than the jitter that impact on the sound....

OK Larry,
But how? Can you help me out?
At the end the dac is only "interested" in a stream of 0 and 1's. Jitter as I understand it, are fluctuations in the stream. Not affecting any 0 or 1.
It is what the wind is doing to the national flag of a country. Think of a flag  lying on the ground, fixed at two points where normally the pole is. Whatever wind will do to the flag the information on (or is it in?) the flag will be intact. The more wind the more "jitter the flag will have. No wind and a perfect "still" laying flag would be "zero" jitter.
Accepting that the transport is not changing or missing one bit of the 0 and 1's and also faithfully respect their "place" in the stream, meaning the image on the flag is fully intact, what else can be wrong in the digital input signal, so the DAC can sense this hidden "property" of the transport?

[Larry]

Accepting that the transport is not changing or missing one bit of the 0 and 1's and also faithfully respect their "place" in the stream, meaning the image on the flag is fully intact, what else can be wrong in the digital input signal, so the DAC can sense this hidden "property" of the transport?

Who is going to accept that the transport is not changing or missing one bit of the 0 and 1's etc?

I am not going to accept that.

[JohnR]

This might help - ? eg

Interleaving allows even larger errors to be corrected than with parity alone. In fact, using parity checking and interleaving together, a good player can correct a burst error of up to 4,000 bits or so. That's approximately one inch of the spiral data track.

http://www.digitalprosound.com/Features/2000/Sept/RecCD4.htm

[kyrill]

Accepting that the transport is not changing or missing one bit of the 0 and 1's and also faithfully respect their "place" in the stream, meaning the image on the flag is fully intact, what else can be wrong in the digital input signal, so the DAC can sense this hidden "property" of the transport?

Who is going to accept that the transport is not changing or missing one bit of the 0 and 1's etc?

I am not going to accept that.

Why not? The zero's and one's are just that.  No difference at all between music and your word or pdf document.
You can easily copy 600 mb of yr documents on cd rom recordable and cpy it back to hard disk to find that you have a PERFECT copy not missing one bit in the copying process. That is what computers are about. You can do this over and over again. So the cd rom is capable of reading and transferring a perfect copy to yr hdd, meaning the sequences of bits are also preserved. But this is somehow static you read static pictures, not a movie. It is, does not need to read the digital stream while it is moving. In streaming dig info jitter happens, but not the loss of zero's and ones. In case this would happen (ugly disk, deep scratches etc) it is not a property of the transport but of the "ugly"disk,

John: Thanks for the link, loosing one's or zero's is not a real issue

[Larry]

Why not? The zero's and one's are just that.  No difference at all between music and your word or pdf document.
You can easily copy 600 mb of yr documents on cd rom recordable and cpy it back to hard disk to find that you have a PERFECT copy not missing one bit in the copying process. That is what computers are about. You can do this over and over again. So the cd rom is capable of reading and transferring a perfect copy to yr hdd, meaning the sequences of bits are also preserved. But this is somehow stat ...

CDROMs and music CDs use different low level coding technologies.  The reading mechnism of CDROM is different from that of CD. The "a PERFECT copy not missing one bit in the copying process" is what you see after error correction. Music CD uses a simpler error correction technique.  

A lot of errors could find their way eventually into music bit streams due to  mechanical, optical, electric and electronic causes in the transport.

[Larry]

This might help - ? eg

Interleaving allows even larger errors to be corrected than with parity alone. In fact, using parity checking and interleaving together, a good player can correct a burst error of up to 4,000 bits or so. That's approximately one inch of the spiral data track.

http://www.digitalprosound.com/Features/2000/Sept/RecCD4.htm

What about non-burst errors, or burst errors beyond designed error corrction capability and the errors caused in the transport after the pick-up error correction?

[Larry]

This might help - ? eg

Interleaving allows even larger errors to be corrected than with parity alone. In fact, using parity checking and interleaving together, a good player can correct a burst error of up to 4,000 bits or so. That's approximately one inch of the spiral data track.

"a good player can correct ... " which means that there are not so good players existing that can not correct that much, which means that errors may remain in the music data, which means that DACs can do nothing about this, which means that players, or transports are not born equal -- some are good, some not.

[kyrill]

CDROMs and music CDs use different low level coding technologies.  The reading mechnism of CDROM is different from that of CD. The "a PERFECT copy not missing one bit in the copying process" is what you see after error correction.
So this makes the error correction algoritm almost perfect too!
Music CD uses a simpler error correction technique.  
A lot of errors could find their way eventually into music bit streams due to  mechanical, optical, electric and electronic causes in the transport.

Ok but will you ever notice? Or do you suggest, because it is just music , the industry allows such a more simpler algoritm that it passes faults (next to jitter) that you can actually hear? (based on clean unscatched cd's and using a mainstream, but not bad player)

But even then,  accepting yr critique, you define a "fault" which is in every transport and in every cd player (more or less) and therefore a fault in the medium itself. This will be true for integrated cd players as well and nothing any DAC can do something about.

[Larry]

Ok but will you ever notice? Or do you suggest, because it is just music , the industry allows such a more simpler algoritm that it passes faults (next to jitter) that you can actually hear? (based on clean unscatched cd's and using a mainstream, but not bad player)

All CDs, clean and unscratched, contain errors. The CD pressing industry has defined a standard for the maximun amount of errors allowed on each freshly pressed CD!

But even then,  accepting yr critique, you define a "fault" which is in every transport and in every cd player (more or less) and therefore a fault in the medium itself. This will be true for integrated cd players as well and nothing any DAC can do something about.

Error is error and fault is fault. Error is not fault.

Error is the reality we all have to live with. Fault is something you can try to avoid.

All CD may contains errors and some more errors may added to the music in a poorly designed/built transport before it's fed to the DAC. A good transport can correct more errors on CDs or conceal errors better and causes less errors subsequently.

[kyrill]

Error is error and fault is fault. Error is not fault.

Error is the reality we all have to live with. Fault is something you can try to avoid.

All CD may contains errors and some more errors may added to the music in a poorly designed/built transport before it's fed to the DAC. A good transport can correct more errors on CDs or conceal errors better and causes less errors subsequently.

It is funny to see how clear everything seems to be for you.
Your ear make errors too. Your brain is a very subjective device to correct the "errors" of yr sensory specific organs. But will you notice this? I am sure you or I  will not unless you fool the brain by feeding it an "error" it then tries to correct.
You do not answer my question. Can you actually hear the "errors" you so firmly acknowledge in the context of a clean cd and a normal cd player And of course discernable errors ( or faults?) on the cd itself, perceivable by any good cd player is a property of the cd.
we were mainly talking about the properties of transports and dacs, and not the chain before that.
Yr interesting difference between faults and errors. What used to be errors in the past, then has become faults today.

[AKSA]

Hi Larry,

Good to see you back!!  Your points are always clearly put, and well thought out.

I trust life treats you well!

Cheers,

Hugh

[Tinker]

I have followed the recent series of posts with some interest. Jitter is a vexed issue, not in the least because measuring and characterising it is very hard. Finding its sources is even harder.

I should clear up one misconception: the main source of transport/cable related jitter is that the clock signal is buried in the S/PDIF data stream. This is bad. Because the clock is extracted from data that is encoded usign a bi-phase mark system, skewing (due to cable properties), fluctuations (caused by any number of things, including power supply loading, RF, crosstalk etc) will distort the timing of the edges. Recovering the o's and 1's is trivial compared to recovering them at the right time. CDs use eight-to-fourteen modulation, cross-interleaving and some parity bits, so a clean CD will give fair robustness to errors, but jitter remains as the primary goal of such approaches is signal integrity not signal timing. So everything you guys have said is true, however, jitter is yet another pile of sludge on top of this. Let me charge on here...

The main jitter problem comes from transport and output premamp power supplied modulating the on-board clock and other digital circuitry causing jitter. The classic solution is to put the DAC in a separate box with its own supply. However, the DAC receivers use PLLs to recover and smooth out the clock, which have to allow for a degree of slop in precise transport speed (the standard is +/- 400ppm!) and jitter on the incoming clock - thus the transport does affect the recovered clock, albeit somewhat diminished dependeing on how good the PLL is. The PLL's performance is a basic limiting factor in DAC jitter. All else being equal optimising the PLL gives you a major performance improvement. The remaining problem is that signal dependent artifacts can still intrude on the recovered clock in a number of ways, and since the two systems are effectively synchonised these artifacts are of the worst kind - signal correlated. This tie can be broken by "desynchronising" the systems (transport and DAC) which can be accomplished using a FIFO and a few other tricks. The rest is just good design: power supply regulation, layout, optimsed component choices and careful attention to grounding and RF.

It is true that the transport and cable will always have some impact on the final result (usiggn the current interface that is) but it is possible to reduce this by a large factor if not an order of magnitude or two, and that's all that's needed to put the effects below the noise floor.

As far as errors go, you can use somethign like exact audio copy to make a crude log of how many and what kinds of errors are on discs. The worst error you get on CD is a "fatal" one requiring interpolation. Philips used to make a test disc which had tracks with deliberate errors of different kinds so you could check the transport and error-correction system. Larry is spot on. There are a lot of dirty transports out there, but it does take a lot of data corruption to actually corrupt a sample. I will endeavor to do some tests to find out how much corruption is required to actually mess up a sample. Could take me a while.


Hope this helps. Pardon the ranting.

T.

[Tinker]

I recalled that there was an error-rate discussion in the Pro AUdio forum last year and in fact Glenn has produced a study of error-rates in recordable CDs and Bob Katz of Digital Domain/Chesky Records has kindly published them. Of course this data pertains to errors ON the disc, not so much coming off it due to poor players. I will endeavour to find out what the maximum BLER is for a CD to pass redbook standard (yes, manufactured CDs do have errors!)

The results of Glenn's tests are here:

http://www.digido.com/portal/pmodule_id=11/pmdmode=fullscreen/pageadder_page_id=75

Note how few of the errors are uncorrectable. Still, if you have a poor player then this rates is moot. Tracking, lens and wobble are important factors in read quality.

More news as I get it.

T.