Showing 1 of 315 conversations about:
WilliamTse
103
Founder, Airist Audio
Jun 6, 2018
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Hey Folks,
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!
Jun 6, 2018
elira
199
Jun 6, 2018
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I just see a total lack of integrity from you and your company. Somehow you ended up with a board identical to the Hibiki and somehow you want to trick people to think it was just a coincidence. That's sad man.
Jun 6, 2018
bunkbail
177
Jun 6, 2018
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It goes beyond pathetic. He went about DSP and filters to give him back some designing credibility but without actually addressing the main issue.
Jun 6, 2018
Huxleigh
83
Jun 6, 2018
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Jun 6, 2018
Inorbit
79
Jun 6, 2018
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Not trust worthy!
Jun 6, 2018
WilliamTse
103
Founder, Airist Audio
Jun 6, 2018
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As I mentioned above, our engineer found several existing boards during his research, including the Hibiki, and drew on them for the basic layout of the top board. Although the component positions are similar, this is a 4-layer PCB with trace routing and ground plane design that is not visible in the photos.
Jun 6, 2018
WilliamTse
103
Founder, Airist Audio
Jun 6, 2018
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I shared the story of our development process, from the inspiration of the Soekris to finalizing the design for this launch. During that process, our engineer looked at numerous R-2R implementations when drafting the top board, including the Hibiki, to establish a starting point. The top board on its own did not give us the sound we were looking for from a R-2R. The DSP and filter adjustments, along with reclocking and other enhancements in the bottom board, are key to the sound of the RDAC as a whole.
Jun 6, 2018
bunkbail
177
Jun 6, 2018
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Yeah yeah keep on spewing BS. Based on what you've just said, you don't even need R2R to begin with. You can reach the sound you wanted using delta sigma chips, just tune the DSP and filter and reclocking or whatever to your liking, and be 100% legit and trustworthy rather than do things the way you're doing right now.
Jun 6, 2018
WilliamTse
103
Founder, Airist Audio
Jun 6, 2018
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R-2R and delta-sigma converters have different requirements and characteristics, so the DSP and filtering is tuned to supplement and enhance the particular topology. The same filters that make an R-2R sound great may not work as well with a delta-sigma, and vice versa.
Jun 6, 2018
jdeoxys
205
Jun 6, 2018
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OI YOU GOT A LOICENSE FOR THAT PEPE?
Jun 6, 2018
bunkbail
177
Jun 6, 2018
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i give credits when its due. creative commons thingy, yeah. PepeHands
Jun 6, 2018
Tigerman
402
Jun 6, 2018
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I get your points, that the top board in question is not the whole DAC, and overall I think you are trying to help people see that designing any audio product takes a lot of work and passion even though of course nothing is designed entirely from scratch using only first principles. BUT why can't you see that's not enough?? Your R-2R board looks identical to the Hibiki board, but you haven't acknowledged that, so people see your explanations as evasive. "numerous R-2R implementations ... including the Hibiki, to establish a starting point " "several existing boards ... including the Hibiki, and drew on them for the basic layout" We are all thinking "BULLSHIT! Cmon, they look identical!" I can only imagine that you or your engineer did copy the Hibiki layout, but thought that you'd done enough enhancements to call it your own design overall. What else can it be? How can you insult everyone here by thinking that your evasive answers will be enough? Even more, how can you let down your own hard work by letting this issue overshadow everything else?
Jun 6, 2018
killerwingnut
24
Jun 6, 2018
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I'm not an electrical engineer, but it looks like all they did was leave off the HIBIKI silkscreen on the top board...
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.
Jun 6, 2018
WilliamTse
103
Founder, Airist Audio
Jun 7, 2018
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Hey Tigerman,
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!
Jun 7, 2018
Tigerman
402
Jun 7, 2018
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I'm not saying you're wrong about all the extra design work you've done. But are you saying everyone else here is wrong? Until you acknowledge our side, you'll have a hard time getting people to see your side. (Have you noticed a lot of comments along the line of "good luck to you"?)
Jun 7, 2018
Huxleigh
83
Jun 7, 2018
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In fairness to @WilliamTse, there's no reason for him to "acknowledge" something that doesn't comport with his version of events. It's patently absurd for someone to admit fault on their part when (according to them) none has been done. Doing so unnecessarily is just a easy way for people arguing in bad faith to hang you with your own ham-fisted attempt at reconciliation. Don't do it.
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.
Jun 7, 2018
Inorbit
79
Jun 7, 2018
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Acknowledging to be a serial killer doesn't comport to Jeffrey Dahmer's version of events.
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.
Jun 7, 2018
Mael
37
Jun 8, 2018
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Enraged Masses: You a thief!
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?
Jun 8, 2018
ben.park
39
Jun 14, 2018
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@elira bad artists copy, good artists steal, amirite? Guess they don't teach integrity at those Ivy League schools... ;) too busy becoming "whiz kids"
Jun 14, 2018
ben.park
39
Jun 14, 2018
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No, that's not preconceived guilt. That's called prior inconsistent statements according to the law. Or, you know, lying.
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?
Jun 14, 2018
AdviceGuy
20
Jun 22, 2018
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The bottom line is, that is really doesn't matter if you copied the top board to the Hibiki layout...
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.
Jun 22, 2018
ben.park
39
Jun 22, 2018
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No, this is about more than just laziness and profit. This is about integrity and supporting (or not supporting) companies that, were they individuals, we'd choose not to associate ourselves with. If all you care about is better performance, then by all means, continue supporting MD as they facilitate thievery.
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
Jun 22, 2018
Tezz
9
Jun 29, 2018
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You should listen to WAVEDREAM DAC from Rockna-Audio.com and work with Mr. Jitariu.
Jun 29, 2018
ben.park
39
Jun 29, 2018
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LOL "listen to"
Jun 29, 2018
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