Pros and cons of R-2R DAC :
Advantages:
1.R-2R will not convert the clock signal into the output signal.
2. R-2R is not sensitive to jitter while Delta-Sigma DA is much more sensitive to jitter.
3. The output signal is much more precise compared to Delta-Sigma DA .
Weaknesses:
1.THD today is extremely good with Sigma Delta chips; R2R ladders are good too but not as good.
2. Glitches and accuracy of the ladder resistors are very difficult to avoid and require complex technology to resolve it.
Since a audibly transparent delta - sigma dac can be cheaply and easily manufactured and R2R requires more complex methods to over come Glitches and accuracy of the ladder resistors, could the Glitches and accuracy of the ladder resistors in a R2R thats not very well designed cause audible differences.
A lot of the clams made for R2R DACs are extremely dependent on the context in which they're made - and some of them are a bit specious.
I have no idea what "advantage #1" is supposed to mean. The process of converting digital audio into analog requires data and a clock. With PCM data, the data and the clock are parts of the same signal (the timing of the pulses is the clock). With USB, the data is sent in packets, which don't explicitly contain the clock that goes with them, and the clock must be re-created inside the DAC, which can be done a few different ways. Either way, the DAC takes care of the details, creating or regenerating the clock as needed, and then using it in the conversion process. The analog output signal is analog; it does not have or use a clock. Both types of DACs "internally" generate an output that is a series of voltage "steps". The steps are inherent in the process; they must be filtered out; and, when they are filtered out, the remaining analog output is precisely what it should be. R2R DACs
DO NOT somehow magically avoid this part of the process. Some R2R DAC designs do avoid using an explicit filter stage to remove the steps. They do so by incorporating one or more components that is inherently frequency limited, like a transformer, which simply fails to pass the extraneous high-frequency energy. However, they are not "elegantly avoiding an inaccuracy". What they are doing is to remove an accurate and precisely calculated filter, and instead allowing design imitations to do the same job, only sloppily and imprecisely.
Advantage #2 is actually true in a certain context. By all reports, many R2R DAC
chips are less sensitive to jitter than most Delta-Sigma DAC chips. That means that, for a given amount of jitter in the signal that actually reaches the chip itself, the R2R chip will produce fewer artifacts (less distortion). This means that, if all else in the design was exactly equal, the R2R chip might perform better. However, in real life, it simply means that, when designing a Delta-Sigma DAC, the designer has to be a little bit more careful about minimizing jitter. This is not especially difficult to achieve. (And note that we're NOT saying that an R2R DAC will perform better with input signals with a lot of jitter. First off, an input signal should not have a lot of jitter to begin with. Second, all DACs have internal mechanisms that eliminate or drastically reduce jitter before the signal reaches the DAC chip. Third, virtually all R2R chips have more serious issues that overshadow this one.)
Advantage #3 is simply an unsubstantiated claim. The output signal produced by most Delta-Sigma DACs is far more precise than the one produced by most R2R DACs... and this is especially true with higher bit depths. There are many R2R DACs that can reproduce a 16 bit signal relatively accurately, but almost none that are accurate to 24 bits. The term "precise" is ambiguous; it can refer to any measurement, or combination of measurements, you choose to use. By almost all commonly used measurements, the output of most Delta-Sigma DACs is FAR more accurate than that of most R2R DACs. Fans of R2R DACs will point to the one or two performance metrics in which R2R DACs do well and claim "they're the ones that you hear the most", but that is... err... a minority opinion. Also, incidentally, most of the so-called "time accuracy issues" usually attributed to Delta-Sigma DACs are really associated with oversampling. Therefore, they are equally true for all oversampling DACs - whether they are D-S or R2R. (Oversampling has huge benefits and minimal drawbacks - so is really necessary for a DAC to perform well - especially with a 44.1k input sample rate signal. Non-oversampling DACs of either type perform quite poorly - by almost all performance metrics. Although, again, fans of NOS DACs will insist that the few things they get more or less right are "the important ones".)
Both weaknesses are spot on.... I would also add that the complex technology needed to overcome glitch issues is often rather fussy (which is why some R2R DACs require an absurdly lengthy warm-up before they perform properly). The complexity also detracts from the price/performance ratio. Low cost R2R DACs often perform really badly; and R2R DACs that perform even reasonably well tend to cost far more than D-S DACs that perform at an equivalent or higher level.
I also feel obligated to comment on one fact that seems to crop up in the marketing literature for many expensive R2R DACs.
They say "the makers of Delta-Sigma DACs use them because it enables them to make a very cheap product that exhibits really good performance".
(But they try really hard to infer that getting excellent performance for a low price is somehow a bad thing.)
