i think i already know the answer to this question but cant seem to convince myself entirely. anyway, what is more important for processing the digital signal, a dsp or a dac? and would one prefer 2 dsps or say 2 dacs per channel? what i am particularly interested in is for processing dolby digital, dts, circle surround, etc. NOT sound fields and dsp modes and NOT music although i would be curios about sacd or dvd-a processing... anyway i hope someone can reconfirm my thoughts.

A DAC and a DSP chip perform two different functions (generally). The DAC is what converts a digital bitstream to analog. A DSP chip is what does the calculations on a digital signal to do things like room simulations, bass management, EQ, mixing and other functions. A DAC chip is not supposed to change the signal in any way, but to just convert it from digital to analog as cleanly and accurately as possible. A DSP chip is used as the compuational engine to change the signal in some way. Having more than one DSP allows more complex calculations to be made in real time, such as more realistic reverb fields and more EQ bands to be made. In this sense it is no different than having more than one processor in your PC to do number curnching.

Chips that do things like Dolby Digital and DTS decoding are hybrids that use DSP engines to decode the digital bitstream and DACs to output the result as analog (a very rough expalation). Chips like the Cirrus logic would do their soundfield enhancements by DSP processing.

None of this is really in the control of the buyer except in the sense of more expensive equipment generally having more computational horsepower available to process a signal. However, the mere presense of more DSP power does not guarantee that the programming that those DSPs are carrying out is necessairly as good as a less expensive unit that may have better programming built in to take better advantage of more limited computational power.

This is just like in the PC area - some programs are better than others at doing the same task, and some are more efficient than others.

[This message has been edited by soundhound (edited April 04, 2004).]

so what you are saying is that a better dsp is more important that a better dac?

Generally, if you just want to listen to music with no added processing, you dont't even need any extra DSP processing capability. You would only need to have a DAC to convert the signal from digital to analog (this is ignoring such things as the ICs needed for digital oversampling and filtering carried out before D/A conversion). The only thing that more powerful DSP chips would buy you would be more precise processing of a signal if you wanted to change it in some way, like EQ, room simulation or something like that.

A DAC is only used to convert the signal from digital to analog - if this is all you want to do, then that is all you need in your player. If you want to process the signal in some way beyond just the basic conversion, DSP computation would be needed, and just like in a PC, more processing power gives more precise results (and more approaching real-time).

There are so many variables involved to the decisions a designer makes in a finished piece of equipment that it is all but impossible to buy something purely on how many and what kind of DACs and/or DSP chips it has. It would be like buying a car strictly on how many cylinders it has - this would ignore the very significant differences in design that can make engines of equal cylinder count very different in real world performance.

However, very generally, you get what you pay for with higher end equipment using a higher grade of DAC and generally more DSP power available for processing tasks. How that computatational DSP power is used is up to the skill of the programmers and designers.

[This message has been edited by soundhound (edited April 05, 2004).]

very specifically for dts, dolby digital, etc. ONLY what would one want better dsp or dac... from what you are saying the dsp does the processing and the dacs just convert its (dsp) processing into analog. which is what i know as well, and seeing as the dsp is upstream (so to speak) of the dacs, the dacs would be limited on how good the dsp would be. if the dsp is not doing a good job then the dacs never will, but if the dsp is doing a good job then and only then can the dacs make a difference. that is pretty much what i thought...
however its curious that a lot of companies employ 2 or more dsp chips while hardly any employ more than one dac per channel. well i guess it is not so curious if the dacs are important, but the products that you find 2 dacs on a channel are top of the lines.
if you look at two solid audio companies, yamaha and denon, yamaha's focus is on dsp processing and denon's focus is on dacs. and while i know that both are USED IN COMBINATION and one does not make a product superior, yamaha emphasizes dsp (they even use their own!) and denon has 16 dacs in differential configuration which you dont find except in levinson gear (or its likes).
i always thought dsp processors were for sound fields and not dolby digital, dts, etc. but they are not, and eventhough dolby doesnt require quite as much processing (just reading and routing) as simulated fields, i suppose they are more crucial (strictly speaking) that dacs.

Decoding Dolby Digital and DTS is generally done by a dedicated, application specific IC that has DSP processing and the DACs built into their design. The decoding itself is done by a DSP engine.

You don't need more than one DAC per channel of audio unless you are running differential output, which is something that is not done all that much. Just like you only need one power amplifier per channel, the same thing holds for the DAC. If somebody is using more than 2 DACs per channel (differential), I would have no idea what they are doing with them since their presence is not required to convert to analog.

how much value would you place on 2 dacs in differential configuration? meaning how much better would they be than 1 dac of the same quality all other factors the same?

A differential DAC configuration is essentially like a balanced circuit where one DAC is "going positive" while the other is "going negative". This configuration lends itself to balanced audio connections since no additional conversion is needed to create a balanced analog output.

Differential configurations have some noise and distrotion advantage over single ended configurations, but I seriously doubt that anybody, including myself could hear the difference in an A/B blind comparison. A common way to design a differential DAC configuration is to use a regular stereo 2 channel DAC for each audio channel. The left and right channels of the DAC are used for each polarity of the single audio signal.

I would much rather have a really good single ended DAC configuration than a lesser quality differential one that was just marketing driven.

Like all things, what matters is the final sound, not the number or configuration of DACs or DSPs. A good designer can make a combination of good quality parts perform better than premium parts in the hands of a less talented designer. A great carpenter could build a better house with an el-cheapo hammer than I could with the best hammer in the world.

Soundhound,

What do you think of the following statement?

Sony docs say that the DACs employ a new "multilevel" design with multiple equal-value current sources that are summed to form the output. What makes for a lower error conversion is that the specific sources used for a particular summed output value are randomly selected at each iteration so that errors are not accumulated or repeated. These DACs are the same balanced-output, current-output DACs used in the SCD-C555ES (reviewed by Larry Greenhill in the October 2001 Stereophile), where three of these dual-channel chips serve the six channel outputs. The XA777ES uses six, with one entire dual DAC used per channel for the multichannel outputs and three dual DACs paralleled for each channel in stereo, to improve dynamic range.

Is this a marketing ploy, a valid parellel processing as claimed or just an overkill that produce no discernable difference to human ears?

anyone know of a website/page/article that compares different manufacturers dsps and dacs compared to one another? i can find some that show one manufacturers, but how they compare to other brands is obviously not listed...
or just some input as to which manufacturers are superior, i mean in between crystal, burr brown, motorola, akm, wolfson, etc. who is best... or are they all very close considering comparable models.

[This message has been edited by curegeorg (edited April 06, 2004).]