So, from reading over these techs posts regarding the R2R, together with the mentioning of Cayin N7 by
@hongky . I think I found some more assumed conclusions, just based on what I know and think I know, this is not definite technical information. Cayin R-01 module, Ru-7, N-7, are all seemingly sharing the same technical designs with different implementations, whether it is into a dongle form, or a compact whole motherboard, or a complete DAP solution. The D16 DAC conversion from Ibasso is similar but taken to another step further with it being a dedicated and stand alone DAC solution.
Basically, what I got out from all of these is that The R2R ladder is one of the Low Pass filter Stage. I also think that because DAC is a little complicated, with different marketing, people get even more confused. Therefore, from what I know, I can say this. All of the DAC is whether
Over Sampling or Non Over Sampling. It could be whatever Topologies, whether it is R2R or Sigma-Delta, it wouldnt matter.
The confusing part is that the earlier DAC technologies was more of a "discrete design" or we would call it a Resistor ladder converters. When we mention about Resistor Ladder or another term of Resistors to Resistors, we simply sum up all of them to carry R2R designs. Now, let dissect into these confusions
1/ R2R converter, this is the conventional Resistor ladder conversions. Basically, it took all of the binary coding, and pass through a series of resistors in sequential orders, and during this process, especially for D/A and not A/D, the conversions can follow Nyquist standards to stick with the most minimal bit that we have, a 16 bits. This means that we will have to deal with Most significant and Least significant bit. The differences between them, the voltage crossing at a certain gated threshold can cause significant distortions and errors. Therefore, technically speaking, the conventional design is Non Over Sampling, with a whole lot of distortions, floor noises, errors....etc... you name it. This is where people also love conventional R2R converter. The same as people who love tubes and it distorions
.
My argument is that, music in itself is just noises and harmonic distortions, right ? LOL. I love conventional R2R conversion, and also love Tubes
Now, because of this, the engineers found out that if they were to have feedback loops implemented during the conversions, it would improve the resolutions, but in trade off for more components and spaces needed. This is where OverSampling topology came in.
2/ The modern Solution of R2R topology: This is no longer a conventional R2R, or following the NOS topology, it is OS topology. Because having the whole array of resistors of 16 bits together with OverSampling in discrete lay out will need a lot of spaces, and components, together with the tolerances in between them. This never came to light until recently where FPGA and programmable chip was a thing. FPGA solves many problems for the engineers, from having to fabricate their own chips, to just written algorithms with Oversampling factors and specially order it to be programmed with FPGA to solve the problems. Since it is programmable, engineers have the options to whether or not to compiling the whole conversion on a chip, or splitting it out. One of the Example of a whole conversion would be Chord as a brand, they are touted to known with their FPGA technology.
Beside using FPGA, of course you can use other meaning to convert digital signals as well, by using computational power and a written algorithm, then stored it into a file format of DSD. We call this Offline Conversion. This leaves all of the DAC systems to be as an Live conversion, because it takes in multibit PCM and convert it......you guessed it, toward to 1 bit DSD. Are you confused yet ? simply put, all of the Digital coding, before becoming analog signals, will have to be a 1 bit signals, and then passing by Low pass filter networks, before becoming Analog.
Then there is DXD to add into the confusion, It is just glorified PCM multibit and isnt directly related to 1 bit DSD
3/ Why Cayin, Ibasso is claiming 1 bit DAC as a title ? Isnt all DAC converting multibit into 1 bit before passing to LPF (Low pass filter) ? That is right, and they claimed it so, because They are implementing a network of Resistor ladder for the filtering processing, instead of only be using an opamps with feedbacks for example.
Is it R2R still ? Well, it is R2R alright ? but it isnt the conversion itself. Rather it is the filtering or the aftermath of the conversion
So what is really a conversion here ? well, it is the SRC or Sample Rate converter, or an FPGA if they used it instead.
So then, it means people who seeks for FPGA can rejoy with this ? Basically, Yes, it is similar to Sony/Chord topology, but with a tweak, and of course, the algorithm and firmware is really all that matters
4/ Finally, is it R2R ? is it Sigma Delta ? is it Over Sampling ? is it Non Oversampling ?
Again, there are only 2 topologies, NOS and OS. Because NOS in a typical/original Resistors ladder design cant be adequate for high resolution, the new innovation solutions is to adopt Over Sampling but hybridizing it with R2R analog filtering . It is Safe to assume that all of the modern R2R solutions are playing it safe by incorporating OverSampling. Because it is OS, it is the same as Sigma Delta
Can it be NOS as well as an option ? Good question, but it depends on the point of engineering. FPGA/SRC chips have it own limitations. If it was originally designed for a NOS as an option, then it could be incorporated, otherwise it is not going to be an option. Some FPGA solution can go for using an Oversampling with 1X factor instead, which make it an Oversampling yet without Oversampling....we may think of it as a NOS, or more precisely a +NOS feature.
I am not sure if the D16 will incorporate NOS as a feature, or what exactly is the rate of SRC for OS ? it would be very interesting to find out. Also, the measurements and it specifications can tell for a story by itself, and technically as a Converter, it is a primary goals. Then how it sound ? the main goal and objective ? to be subjective ? only one way to find out
For all that said, I am extremely interested in D16. Something to compete against the like of Sony/Chord ? why not ? or we can trim down the herd and .... selectively be saying, Sony only has Walkman with Class D output and no true line out, while Chord is an all in one solution of FPGA together with a lot of IC-Opamps design rather than resistive ladder for LPF....this really puts Cayin/Ibasso into the spot lights. Before I forgot it, why is R2R LPF a point of interest ? Because with this, the analog tuning can be stretched further
. Because, technically, and honestly, There can only be so much our ears can hear, whether it is floor noises or distortions, even when we say the better the measurements is the more desirable, but the tuning of the signature across the board is actually an impactful factor. Therefore, having a better way to tune your own analog signature, is absolutely desirable.
Why am I more gravitated toward the D16 ? well, because it is a dedicated solution toward high-end system with dedication, and not just aiming toward compact solutions like the Ru7.
Last and not Least, will Cayin be using the same Technicalities as Ibasso ? I personally Dont think that they are similar. There is zero way to tell exactly, and I don't think either of them want to disclose it either, as said above, having their own Discrete Low Pass Filter is having their own impact into their own Canvas and Arts which will yield unique results. The possibilities are endless, they could be using different factor of feedbacks, different set of values...etc....So, they are similar but also very Uniquely Different. Asking this question is like asking if both Picasso and Davinci were both using paints/canvas/brushes, would they be having the same arts