[backdrifter]

edit

 

[tiberian]

great spec /= great sound. afterall you need to use your ears to judge.

 

[gsferrari]

A Good CD player is about :-

Transport
DAC

Both...

A bad transport, unstable, noisy etc. Jitter etc. all contribute to a bad CDP.

I think the transport is more important than the DAC. Why? you can buy a good external DAC and use it with a good transport...

 

[soundboy]

Your question assumes everyone uses a CD player connected to a receiver with a build-in DAC. There are still many of us who connect our CD players using their analog outputs, with the CD player's DAC doing the processing. At the same time, DAC is only one part of the CD playback chain....there's also the transport, the implementation of that DAC, etc....

 

[gurus]

Like they say 'its the source, s****d'. If you can't get a decent jitter free signal to the DAC, any equipment downstream from the player won't perform to its capability. From the CD-> Transport ->DAC ->Preamp/Amp ->Speakers. The sound is only as good as the weakest link in the system. DAC's now generally sound very similiar, its the worst dollar spent/perfomance benefit. A good CD pressing the best. Transport and speakers would be next. Thats generally speaking.

 

[Ferbose]

Quote:

Originally Posted by gurus If you can't get a decent jitter free signal to the DAC, any equipment downstream from the player won't perform to its capability.... DAC's now generally sound very similiar, its the worst dollar spent/perfomance benefit. A good CD pressing the best.

I respectfully disagree.
I would argue that an ideal DAC should not be influenced by jitter coming from S/PDIF interface. The fact that transport and digital interconnect affects the sound reflects a flaw in DAC design. A new generation of hi-end DACs have come into the market and boast of total jitter immunity. In my experience, a good DAC gets rid of digital artifacts commonly associated with CDs and make music more enjoyable. Other aspects improve with better DAC as well (resolution, airiness, soundstage, bass etc.), but the effects are more minor.

Although newer DAC chips claim to have better specs (higher sampling rate, longer word length, higher S/N ratio and dynamic range) than the older ones, they don't necessarily sound better. IMHO it is still the analog circuit in the DAC that counts the most (power supply, I/V converter, filters). Some very hi-end DACs intentionally use out-of-production 44/16 DAC chips even today because designers feel those sound better. In a nutshell, the spec of the DAC chip being used has little correlation with actual sound quality. While decent receiver offers good bang-for-buck, the fact that it is packed with so many things means that the quality of each part will be negatively affected.

 

[Samuli]

First of all specs like 24bit/192khz dac and the likes isn't all there is to that. 24bit dac could easily sound worse than a good 16bit dac. Though the analogy is loose, I'd say it's the same as saying 100w amp will sound better than 60w. Yes, the 100w amp performs better in some measurable area (can play louder according to specs) but it has little or nothing to do with the sound quality ultimately.

And what comes to the transports, jitter really shouldn't be any problem there, nor is the electrical noise from power supply and other components found in a transport. Digital signal is totally unaffected by electrical interference in practise: Let's assume that a transports s/n ratio is as bad as 60db. This would mean that the actual useful signal is million times stronger than the noise. What really matters in digital signal is the dips and peaks in it, so it's pretty safe to assume that this 1/10^6 noise affects the DAC in anyway and of course, as dac only takes usage of the dips/peaks, noise in the digital signal isn't carried over to the analog.

Also, all jitter caused by the digital signal path is also dismissed in the dac. This due the fact that in digital signal timing info and the actual signal are tied together in a manner they always stay in time, in respective to each other. So only places where jitter will occur are the A/D conversion and the D/A conversion where signal becomes time-dependant again (say analog). Sadly it is that the studios A/D conversion might be the weakest link in the digital audio chain and there is absolutely nothing we can do about it.

 

[drminky]

You have to also consider the dac implementation - internally and externally. Internally, what matters is not so much the amount of upscaling but the algorithms and engineering decisions used to achieve the upscaling/converting. This has a DRASTIC effect on the quality of the resultant waveform. You can see how this happens visually by upscaling an image in photoshop etc, and flicking through the different scaling filters - a huge difference! No one solution will be perfect, they will all have advantages and disadvantages in varying proportions, and each choice made will impart its own distinct 'flavour' to the sound. Some manufacturers will be primarily concerned with getting 'flashy specs' like '24/192' into a chip at a low cost, so won't be interested in spending lots of time and money RnD playing with different mathmatical formulas. Others may put a lot of time and money into testing hundreds of different possible implementations to get a great sound, even if the specs are not all that impressive.

Externally, a dac is one of the most sensitive devices in hifi to quality of power supply, so good power regulation is vital. Also to consider is the quality and implementation of the output stage (a mini amp in itself), the quality of the transport and accuarcy of the clock etc.

Big $$ seperates tend to be 'overspecced', ie maxed out as much as possible, whereas recievers tend to be an engineering compromise - what's often most important is the quantinty of functions over the quality of the individual functions. I for one don't want my dac section and phono stage having to share power and proximity to my amp section..

 

[ssportclay]

The thing that struck me the hardest when I first received my SACDmods Denon 2900 was the increase in dynamic slam caused by the new discreet analog output stage,(zap filter).I also have to turn the volume down as compaired to before the Mods.A new DAC will not even address this issue.Most CD players sound digital and lame to me now where the SACDmods Denon 2900 sounds like music.

 

[Samuli]

Quote:

Originally Posted by gurus If you can't get a decent jitter free signal to the DAC, any equipment downstream from the player won't perform to its capability. From the CD-> Transport ->DAC ->Preamp/Amp ->Speakers. .

The jitter induced by transport completely disappears in the dacs receivers buffer. From there it is converted by using the dacs clock. Transports clock signal has to be only precise enough not make receivers buffer over-/underrun.

 

[drminky]

Quote:

Originally Posted by Samuli The jitter induced by transport completely disappears in the dacs receivers buffer. From there it is converted by using the dacs clock. Transports clock signal has to be only precise enough not make receivers buffer over-/underrun.

sigh, this would be lovely if this were the case, but AFAIK, the situation still stands that for 99% if not all of the dacs in the world it is sadly not.

From Stereophile:

'The transport's S/PDIF digital output drives the digital processor's input receiver. The input receiver generates a new clock by locking to the incoming clock in the S/PDIF datastream with a Phase-Locked Loop (PLL). This so-called "recovered" clock then becomes the timing reference for the digital processor. When your digital processor's "lock" or "44.1kHz" LED illuminates, the processor has locked to the incoming clock signal. If this recovered clock is jittered, the word clock at the DAC will also be jittered.

It is commonly believed that transport jitter is rejected by the input receiver and not passed to the recovered clock. Unfortunately, that's true only above a certain frequency, called the "jitter attenuation cutoff frequency." Below this cutoff frequency, the input receiver and PLL simply pass the incoming jitter to the recovered clock. The popular Crystal CS8412 chip has a jitter attenuation cutoff frequency of 25kHz, meaning that the device is transparent to transport jitter below 25kHz. The input receiver essentially acts as a low-pass filter to jitter. Note that jitter energy with a frequency between DC and 40kHz produces audible degradation.'

 

[markl]

A DAC chip is just one small part (although an important one) of any digital component. Having a high-quality DAC in your receiver is great, but if it gets fed a less than perfect data stream (jitter), there are issues, and if it hands off that data to a cheap, noisy, poorly designed analog section for output, and if it's all powered by a poorly constructed, inexpensive, noisy power supply, you are definitely not hearing all that the DAC chip has to offer.

 

[Samuli]

And to answer backdrifters question:

You could have better dacs in the CDP. This would of course mean you'd have to use the analog outs of the player. As someone else stated previously, dacs are very sensitive about electrical interference. DAC inside a box packed with complex electrical components and sharing power supply with them isn't the ultimate solution to say the least.

Quote: Who cares what the power supply rails or the ground is doing?
The DAC cares.

 

[Samuli]

Quote:

Originally Posted by drminky sigh, this would be lovely if this were the case, but AFAIK, the situation still stands that for 99% if not all of the dacs in the world it is sadly not. From Stereophile: 'The transport's S/PDIF digital output drives the digital processor's input receiver. The input receiver generates a new clock by locking to the incoming clock in the S/PDIF datastream with a Phase-Locked Loop (PLL). This so-called "recovered" clock then becomes the timing reference for the digital processor. When your digital processor's "lock" or "44.1kHz" LED illuminates, the processor has locked to the incoming clock signal. If this recovered clock is jittered, the word clock at the DAC will also be jittered. It is commonly believed that transport jitter is rejected by the input receiver and not passed to the recovered clock. Unfortunately, that's true only above a certain frequency, called the "jitter attenuation cutoff frequency." Below this cutoff frequency, the input receiver and PLL simply pass the incoming jitter to the recovered clock. The popular Crystal CS8412 chip has a jitter attenuation cutoff frequency of 25kHz, meaning that the device is transparent to transport jitter below 25kHz. The input receiver essentially acts as a low-pass filter to jitter. Note that jitter energy with a frequency between DC and 40kHz produces audible degradation.'

That doesn't really seem to make any sense to me.. The critical thing for the digital processors clock would be to realize that the data coming to receiver is 16/44,1khz.. from there receiver stores the bits to its buffer and feeds it out in time by the DACS own clock. It does not have any usage for the clock signal that came with the signal from there on. It seems to me that Stereophile has never heard of buffers

Now why would the DACS clock need another clocks assistance timing the bits from its buffer anymore than the transports clock needed to read and time the bits from the cd in the first place?

Also what do they mean by digital processor, maybe it's not the same thing as DAC?

 

[pigmode]

Quote:

Originally Posted by gsferrari A Good CD player is about :- Transport DAC Both...

When you move up in price range, those two items are a given don't you think? Primarily what you are also looking for is:

- chassis build quality
- improved internal layout
- critical improvements to the power supply scheme