Hello, I just joined, primarily for the audiophile products. Looking at purchasing the NHT C3 speakers for our new living room. Space is about 15 feet wide by 33 long and they will fire long ways. Space is just for general listening, music room with all equipment is downstairs, so hoping they will fill it with sound nicely. Cheers.
Mar 18, 2024
There have been a lot questions posted here and elsewhere looking for more information on the development of the RDAC. It makes sense, this is a surprising product, and I’m glad to share : )
In the earliest development stages of our R-2R DAC, we were inspired by existing high quality implementations such as the MSB and TotalDAC products. These were some of the most beloved DACs in the audiophile community, and we wanted to achieve similarly excellent sound but at a more affordable price. The first DAC that let us believe this was even possible was the Soekris, which remains one of the best sounding DACs I’ve heard.
So we eventually started working on our own R-2R implementation with our partners at Massdrop, and as with most development processes, that meant studying the existing implementations to understand why they’re great and draw inspiration. One common thread between all of the great R-2R DACs is using sign-magnitude. By nature of how digital circuits work, the typical representation of binary numbers (called 2’s complement) leads to a large number of bits switching at the same time whenever you go from a positive to a negative number. This is called zero crossing distortion. Using sign-magnitude avoids this type of distortion, but doubles the number of precision resistors required per channel. This significantly increases the cost to produce, but we decided that we could not compromise here. The input also has to be converted from the native 2’s complement representation to sign-magnitude, which is done by the control logic in the PLD.
The rest of the basic R-2R circuit comes from this decision to use sign-magnitude. The output from each of the four ladders is rather weak, so we had to give it a bit more current before joining the two halves of the waveform back together and applying a reconstruction (low-pass) filter. These are the four op amps per channel on the output of the RDAC top board. The separation of the input into positive and negative halves requires the ladders to operate from a stable reference voltage, which we achieve with linear series regulator circuits, which are located next to the PLD.
The circuit elements in place, we had to put everything together on a board. R-2R DACs can be sensitive to noise, so it’s important for the component layout to have short paths. We worked with a consulting engineer for this and he looked at a number of existing boards for a baseline, including the MSB, Soekris, and several more that he researched. This included an early version of the Hibiki that he came across on the Chinese audio forums, as well as various open source boards. From there, he laid out our board with a ground layer to further manage noise in the circuit. This 4-layer PCB eventually became the top board of the RDAC.
And then, as it usually goes, we started showing it to some people and not everyone was a fan. We paired the prototype board of our R-2R DAC and some basic off the shelf input modules, and it didn’t sound anything like a great R-2R DAC. There was none of the gentleness or detail we were hoping for. We adjusted the filters, tightened the precision of the voltage regulators, and used better components for some minor improvement. The basic R-2R structure was a start, but it wasn’t enough yet. It was quite a while before we turned to digital signal processing, and that finally unlocked the full potential of the RDAC for us.
The DSP in the bottom board uses carefully designed FIR filters and upsampling to give the R-2R converter a smoother digital input, which then gives us a smoother analog output. It also let us relax the reconstruction filters, which gave us back the details we were missing. Now it was coming together, and the final touches were getting the right set of inputs, fine tuning the DSP, and getting everything production ready and at the price point we needed. And now, with all of that done, the RDAC is ready for your enjoyment.
Thanks for reading and reply below with your questions!
Why cant Tse just say: "Yes, we saw a great way to do it and copied what we could see in the photos, and made the other layers ourselves. It took a lot of work to get it to sound like we wanted, but thanks to Hibiki for saving a few hours of development"
Tigerman's points echo why this is the first drop that I want to back out of, and this would have matched the AAA amplifier in a stack so well.
There is more to the top board of the RDAC than the arrangement of components; there’s also the trace routing and internal layers of the PCB. As I explained, our engineer did refer to the Hibiki when working on the top board, hence the similar placement of components. The visible arrangement of components is close, but the underlying designs are different and were developed independently. Examples of those underlying differences:
1 Ground design - part of the inner layers used to reduce RF noise 2 Output buffer and filter configurations - designed to work together with the filtering on the digital input 3 Routing and component choices - determined by the needs and cost structure of production
I hope this helps clarify for you!
Besides, he has already acknowledged (after initially denying awareness of @sosolar's work) the obvious fact that the boards are topologically similar. Not sure what else you'd expect to him do, given the rest of his claim that the R-2R DAC is the handiwork of Airist Audio and/or a third-party contracted for design consultation.
Stick to your guns and carry on. People will make up their own minds.
Acknowledging to be a moron doesn't comport to Trump's version of events.
And if I ask Charles Mansion he'll say Jeffrey Dahmer's a good man too.
Mr. Tse: Explanation of how the engineer(s) did take the Hibiki's design into account, but the actual internals are self-derived.
Enraged Masses: You a thief and a liar!
Isn't it neat how preconceived guilt works?
Statement #1: "We've been prototyping and building this bad boy since 2015. @sosolar GTFO"
**Ensuing shitstorm because we have eyes**
Statement #2: "Oh, I'm not familiar with this design. The guy in charge of designing our entire PCB "referenced" it (and made an identical copy). So I'm not a lying douchebag, just an uninformed head of a company."But guess what @WilliamTse, it doesn't matter that you're uninformed because as the head of a company, you're responsible for all the actions of all your employees that are conducted within the scope of their employment, and any torts they commit!
Isn't it neat how vicarious liability works?
So what you copied it. It was free anyways... wasn't it?
The only issue is not stating and giving credit due for that top board layout... Very lazy to copy, but probably saved a few months of board layout design...
Could have saved you even more time if you just consulted with the guy too!..
Which is exactly like Hibiki so it just obvious that you should just admit that you used his layout,
So then people can then focus on your evolved circuitry and departure from old design with your extra DSP & overclock & 4layer board tuning...
Which was probably a difficult task, especially the DSP...
The main thing being OVERLOOKED, IS that Your Dac "should now" be better(?), than the Hibiki anyways...
If so, then all massdrop buyers beninfit...
Everybody here is overlooking the result ...is it better..??..
I thinking this Dac should be great, Regardless the drama.
MD can choose to do business with dishonest companies, and it speaks volumes about their ethics, which I for one would assume carries over into the way they treat their customers. And just like MD can choose who to do business with, we fortunately also get to speak with our wallets.
And as many people on these comments have pointed out, this dac is not "better" than many similarly-priced DACs, and they're mostly selling snake oil with their 1. subpar power delivery method (no ground and a freaking power brick due to "lack of space"? Seriously? My Teac DAC and power amp both have enough room with more features despite being the same size) 2. subpar data delivery method (micro USB on a desktop grade device, again due to the aforementioned "lack of space, complete BS when the cost difference would have been pennies) 3. subpar signal delivery method (no balanced outs, when once again similarly priced DAC's with balanced outs are a dime a dozen). They had to compromise on price and then offer faulty excuses to try to pull the wool over our eyes, they compromised their integrity, and ultimately to me this is a subpar product that's dishonest to boot.
But by all means, go ahead and speak with your own wallet. I for one will stick to "better" cheaper DACs. Caveat emptor :D