[Roam]

Quote:

Originally Posted by Ori /img/forum/go_quote.gif That's only partially true. Like all products fabricated on silicon, it takes time and expertise to optimize a design. You will find that the quality of the final product is directly proportional to the R&D invested in product engineering after the initial design was released.

You know what's funny? After the single-bit delta-sigma chips were introduced, engineers came to realized that it was complete crap. So they began work on the multi-bit delta-sigma chips, last I heard they were up to around 8 bits. Not coincidentally, the more bits the delta-sigma chips had, the more accurate they became and the better they sounded. Funnily enough, the more bits there are, the more it resembles the old style R2R DAC chips.

Quote:

I have to say that only a few years ago I too was partial to parallel DACs. I feel that newer designs have reached a point where the converter chip itself is not anymore the weakest link in a DAC system.

Raw output from a multi-bit delta-sigma DAC for a sine wave

Same for a 16 bit R2R DAC

No amount of filtering & signal processing magic is going to make the final output from the former as good as that of the latter. With an actual music signal, it gets even worse for the delta-sigma chip as the waveform no longer follows a predictable pattern. The interpolation & reconstruction algorithms can't deal with the unpredictable changes found in real music.

Quote:

We still have manufacturers who invest enormous amonuts of money in archaic transports and proprietary digital processing, while employing a cheaper approach to the analog section or the power supply. Maybe that's why digital is "only" where it is today...

It is indeed part of the problem. Digital conversion theory is poorly understood by most manufacturers; it's not surprising since the maths involved are quite advanced and pretty much impossible to understand for anyone without a PhD in the field. Even math PhDs will say it's "non-trivial", which is academic speak for "this problem is insolvable".

With regards to power supply and analog section design, this is another area where most people are frankly clueless. Most people think Blackgates, bigger capacitors, fancy regulators, and the latest "audiophile" op-amps are the solution. They aren't. But that's not something I want to get into right now.

 

[kimsnarf]

Here's a quote from AudioAsylum arguing that the newer DACs sound better (like the AK4395 in the Stello DA100).

Quote:

Originally Posted by sendler I like the newer chips ALOT better. I have an Assemblage Dac2.7 which uses twin BB PCM1704 with a CS8414 receiver and even after mods, the sound pales compared to the AK4395 running direct out. The newer chips reveal much more detail and information making the 1704 sound thicker with less distinction between individual instruments and the background. To give a further point of reference, I sold (gave away) my Enlightened Audio Design PCM1000 MK3 and a Monarchy 22A along time ago as these dacs were eclipsed by the Assemblage. Which chips these had I don't remember for sure but I think they both used the PCM63. The 1541 was popular with DIYers because it had enough power in it's output to run with a passive I/V stage. The 2.7 was a great dac, even it needed some mods to the ultra sonic filter to open up the top of the highs. But the AK4395 sound even better. I can only imagine what the newer AK4396 running high res would sound like. The fact that the AKM chips have a voltage output simplifies the design as no I/V conversion stage is required and the exceptional ultrasonic noise performance makes an analog filter on the output optional. The PCM1704 was a great chip in it's day but time marches on. That's progress for you.

Source: AK4395 is my favorite Dac chip

 

[Kevin Sinnott]

Quote:

Originally Posted by kimsnarf /img/forum/go_quote.gif Here's a quote from AudioAsylum arguing that the newer DACs sound better (like the AK4395 in the Stello DA100).

Here's why I think it's more than a little confusing.

The newer DACs might sound better, but isn't what we're talking about when we say 'DAC' really two seperate things? A 'DAC' is a chip, but a 'DAC' is also a unit containing a DAC chipset along with complimentary circuitry, including re-clocking and analog post-conversion opamps and the like. The second description means an old DAC might well be 'in practice' better. Also, a new DAC containing an older DAC might be superior due to designers having had longer to find the best combination of pre and post parts to produce a neutral or euphoric sound signature.

Do I understand this correctly?

 

[Herandu]

It all depends on the knowledge of the designer, and how the mistakes learnt from other DACs on the market have been overcome in his new design.
There is however the great problem called cost. As products such as the TC-7510 DAC have shown, it makes no sense to design a DAC and then charge peanuts for it. DAC buyers expect to have to pay a lot of money for a high-end DAC. Anyone even considering implementing the latest cost saving methods that would allow for DAC prices to drop is surely to have a difficult time selling.
Look at the added cost of putting USB on the DAC-1. How much does the PCM2902 etc cost? I bet that some DAC manufacturers must be looking at Benchmark, Stella, etc. with envy and wish they too could get away with such huge profiteering. The things you can get away with when you add an expensive case inflated price is just mind boggling.
On a related note: it is quoted in the market that Apple make about U$300 profit on every U$500 iPhone sold. I wonder that if they had sold the iPhone for say U$250 how many people would have bought it.

 

[germanium]

Quote:

Originally Posted by Roam /img/forum/go_quote.gif You know what's funny? After the single-bit delta-sigma chips were introduced, engineers came to realized that it was complete crap. So they began work on the multi-bit delta-sigma chips, last I heard they were up to around 8 bits. Not coincidentally, the more bits the delta-sigma chips had, the more accurate they became and the better they sounded. Funnily enough, the more bits there are, the more it resembles the old style R2R DAC chips. Raw output from a multi-bit delta-sigma DAC for a sine wave Same for a 16 bit R2R DAC No amount of filtering & signal processing magic is going to make the final output from the former as good as that of the latter. With an actual music signal, it gets even worse for the delta-sigma chip as the waveform no longer follows a predictable pattern. The interpolation & reconstruction algorithms can't deal with the unpredictable changes found in real music. It is indeed part of the problem. Digital conversion theory is poorly understood by most manufacturers; it's not surprising since the maths involved are quite advanced and pretty much impossible to understand for anyone without a PhD in the field. Even math PhDs will say it's "non-trivial", which is academic speak for "this problem is insolvable". With regards to power supply and analog section design, this is another area where most people are frankly clueless. Most people think Blackgates, bigger capacitors, fancy regulators, and the latest "audiophile" op-amps are the solution. They aren't. But that's not something I want to get into right now.

It is clear from the photos are taken at different volume level. Even though the top one is delta sigma you can still see the bit steps & there are fewer step meaning fewer bits are representing the signal. The signal looks to be taken at - 60db as opposed to -0db in the bottom photo. Most of the noise in the delta sigma is at a frequency well above human hearing range. I would like to say also that noise is not always your enemy as far as obtaining good sound. It can actually help in many cases. Noise can linearize the signal. This is done in both the analog & digital equipment. Noise has been added to magnetic tape since its developement in the form of high frequency bias to shake up the granuals of iron oxide to linearize it. Early digial recordings made from analog tape was better sounding than early pure digital recordings as the tape noise helped to linearize the D/A converters (noise that is called dither is now added in the digital domain to linearize the D/A converters in current all digital recordings. Noise added at the -90 db level makes it possable to record signal as low as -120db in 16 bit system where without the dither noise no sound would be recorded below -90db!! That causes horrible distortion without dither that is plainly audible with music that is recorded softer that -40db. This is the prime reason that they try to maximize the volume levels for digital recordings even though now with dither it is no longer nessessary to do that to get the best sound)

 

[xenithon]

Interesting. I wonder how much an affect it has with older DACs (older chips) that do not support 24-bit signals.....if they are 20-bit or 16-bit, what happens to the "extra" info from the 24-bit signal?

The only "new" DAC piquing my interest is the Citypulse DA7.2x....seems to have a better output stage, caps, low-pass filters etc. than others (then again, I am not too clued up on all the new ones so forgive me if I left other good DACs out

)

 

[germanium]

By the way delta sigma conversion is even more linear in most cases than ladder type DAC's without having to resort to dither but dither still improves them even more. It is also instructive that most of the ADC's in the professional recording studios are delta sigma that are then down converted to PCM through a process called decimation.

The lesson is that unless you have a lot more money than the average joe that ladder type conversion is actually Massively inferior to delta sigma converters. Almost all my DACs in my CD playes & computers have been delta sigma or a combo of delta sigma & ladder since I dumped my denon DCD910 CD player. The best being pure delta sigma for bringing highh quality sound at a reasonably affordable sound. Meridian has been using delta sigma in thier CD players for some time & in my book they beat out big names like Krell & most but the hyper expensive Mark Levinson CD players.

 

[Roam]

Quote:

Originally Posted by germanium /img/forum/go_quote.gif It is clear from the photos are taken at different volume level. Even though the top one is delta sigma you can still see the bit steps & there are fewer step meaning fewer bits are representing the signal. The signal looks to be taken at - 60db as opposed to -0db in the bottom photo.

The top signal is from a 3-bit delta-sigma convertor, that's all the levels it's capable of producing, period. It can produce at most, 8 discrete levels, that signal has either 7 or 8, it's rather hard to make out.

Quote:

By the way delta sigma conversion is even more linear in most cases than ladder type DAC's without having to resort to dither but dither still improves them even more. It is also instructive that most of the ADC's in the professional recording studios are delta sigma that are then down converted to PCM through a process called decimation. The lesson is that unless you have a lot more money than the average joe that ladder type conversion is actually Massively inferior to delta sigma converters. Almost all my DACs in my CD playes & computers have been delta sigma or a combo of delta sigma & ladder since I dumped my denon DCD910 CD player. The best being pure delta sigma for bringing highh quality sound at a reasonably affordable sound. Meridian has been using delta sigma in thier CD players for some time & in my book they beat out big names like Krell & most but the hyper expensive Mark Levinson CD players.

In theory, but even then there's a whole bunch of caveats.
On the workings of delta-sigma DACs (PDF file)
To summarize, there's still a lot of issues to solve and they are far from perfect.

Of particular interest are the following sections of the report:
2.1.2.3 - Jitter & delta-sigma DACs
4.2.4 - The joys of dither
5.2 - Delta-sigma modulator issues, 5.2.3 being of particular importance
6.1 Why multibit, from which I'll quote the following:
Quote:

- Because of the high pulse levels and correspondingly high dV/dt in the transitions, 1- bit converters are very sensitive to jitter. With a B-bit modulator, the output jumps are generally 2B times smaller, - the output error due to a given amount of sampling jitter is thus also 2B times smaller. Also, since there is a signal-dependent number of transitions (remember that a delta-sigma modulator is in practice a pulse-density modulator), the 1-bit delta-sigma is highly susceptible to inter-symbol-interference (ISI). - 1-bit modulators can not be properly dithered. Due to the large error residuals being sent around the feedback loop, even small dither levels will make the quantizer overload. Consequently, the modulator must use low-level dither and the useful input signal range is also significantly compromised. However, high-order modulators does still have good distortion and tone properties due to the complexity and chaotic nature of the feedback-loop. Thus it is argued, e.g. in [Angus01], that this is mostly a theoretical problem.

 

[colonelkernel8]

I always wanted a Theta Chroma 396, but unfortunately, I have never found one that I can buy.

 

[germanium]

We can discuss the theory till we are blue in the face but the fact remains that there are equally adept manifestations of both types at the high end but current ladder types cannot beat delta sigma at any other price point but the very high end. Delta sigma cleans the ladders clock at all other price levels.

 

[tourmaline]

Quote:

Originally Posted by germanium /img/forum/go_quote.gif We can discuss the theory till we are blue in the face but the fact remains that there are equally adept manifestations of both types at the high end but current ladder types cannot beat delta sigma at any other price point but the very high end. Delta sigma cleans the ladders clock at all other price levels.

it all depends...
most important is the analogue stage of a dac, even more important then wich chip to use.

So, a good dac with inferieur output stage will not sound as good as a good chip with good analogue stage.

In other words: if you use a good dac and skimp on the rest of the components, you still are going nowhere!

 

[325xi]

Ahem, so where does Stello stands - it's new, it uses "new" DAC chipset, but it has discrete analog stage, and pretty old-fashion power supply...
What's that - new gen high-end?

 

[tourmaline]

Quote:

Originally Posted by 325xi /img/forum/go_quote.gif Ahem, so where does Stello stands - it's new, it uses "new" DAC chipset, but it has discrete analog stage, and pretty old-fashion power supply... What's that - new gen high-end?

And? it's all in the quality of the components! I can make a discrete section with 50 cents components. The better the components in the analogue section, the better the sound will be. if you read the forums carefully, you'll find that there are still quite some dac's better then the stello.

 

[Gabe Logan]

Quote:

Originally Posted by 325xi /img/forum/go_quote.gif Ahem, so where does Stello stands - it's new, it uses "new" DAC chipset, but it has discrete analog stage, and pretty old-fashion power supply... What's that - new gen high-end?

I have a Aragon D2A with a Stello DA 220 with me.Between the two the Aragon comes off with a not so fatiguing presentation with loads of detail,bass slam,sweet mids and a more natural sound to it.I end up listening for longer periods of time with out any fatigue where the stello could do that after awhile.Most of my listening time goes to the Aragon with the Stello really around for my rock type songs.

 

[tourmaline]

Quote:

Originally Posted by Gabe Logan /img/forum/go_quote.gif I have a Aragon D2A with a Stello DA 220 with me.Between the two the Aragon comes off with a not so fatiguing presentation with loads of detail,bass slam,sweet mids and a more natural sound to it.I end up listening for longer periods of time with out any fatigue where the stello could do that after awhile.Most of my listening time goes to the Aragon with the Stello really around for my rock type songs.

That's all you want, natural sounding, detailed, musical sound. Most new equipment is emphasizing the detail side of the equation. The most important part is musicallity however. And the best old designs still have what it takes; detail and musicallity. It's the whole package, a new shiny chip doesn't guarantee better overall sound.