[JoeWhip]

Speaking of cats, the latest edition to our family.

 

[Jason Stoddard]

2021, Chapter 4
The Second Circle

What is the second circle of Hell? As I write this, I’m away from the internet, so I can’t cheat and look it up. But I’m sure someone knows it. And I’m sure it’s not good. Which is very much unlike our Hel 2. Because this is a heckuva sequel. Definitely Aliens vs Alien, if you know what I mean.

“Already?” someone asks. “Didn’t you just introduce Hel, like, 10 minutes ago or something like that?”

To answer that question, Yes, and no.

Yes, Hel 2 is here already. And, to be precise, we introduced the original Hel something like 17 months ago. Which is a short lifespan, we admit.

Aside: Hel is the shortest-lived product ever at Schiit. ​

But the original Hel’s lifespan wasn’t short because it was a bad product…it was short, because we learned quickly how to make it much, much better. So we did. Simple as that.

Early Grumblings

While the reviews of Hel were mainly positive, most people complained about one of two things:

• No console connectivity—as in, no optical or UAC1 capability. We thought this was fine, because we’d envisioned it as a PC gaming device. And because it found another life in the office—lots of home and remote office workers picked up a Hel. Still, they were right…better to have it and not need it, and all that.
• USB-Micro connectors—as in, these were perceived as old…and, to be frank, a pain in the rear end. Problem was, when we did the original Hel design, USB-C connectors were still painfully expensive. Now, they’ve reached the realm of sanity.

So, Hel 2 is a Hel with optical input, UAC1/2 autoswitching, and USB-C connectors.

But that’s really, really underselling it.

And, it’s not the whole story.


The Transformation

Here’s the deal: even if Hel 2 was only those three changes, that’s a huge thing. It transforms Hel from a neat, great-sounding, PC-only gaming rig (or home office rig) to a neat, great-sounding, one-box, two-way communications system you can use with PCs and Macs and many consoles (PS4, PS5, Switch) and virtually any smart TV and monitors with optical output.

Stop. Go back. Read that again.

Or use this simple bulleted comparison:

• Hel: PCs and Macs (and, yeah, iOS and Android and Linux)
• Hel 2: PCs and Macs and consoles and smart TVs and monitors (and, yeah, iOS and Android and Linux)

Yes.

This is a HUGE deal.

“Well, what about Brutoof and stuff like that,” someone is gonna ask. “I likes my wirelesses!”

That’s cool. We get it. But Bluetooth won’t match the quality of a wired connection. Period.

No. Go back and read that again, too. Bluetooth mangles everything that passes through it. Got Qobuz for its lossless? Well, it’s no longer lossless when it goes through your hyper-convenient Bluetooth connection. Got high-res albums you bought at great expense? Yeah, into the blender they go, never to be the same again.

Yes, the mangling is less these days, what with AptX and AptX HD and LDAC and whatever else is new in the world of proprietary CODECs by the time I write this, which probably gives you a good idea of another reason why we don’t want to get into the Bluetooth morass—between different protocol revision levels and proprietary codecs and intentional-transmitter FCC certification, on top of the compression jiggery-pokery, we decided “we gots better things to do, folks!”

Aside: and yes, I know, this isn’t going to be a decision that’s popular with everyone, or understood by everyone, but it’s what we do. Please excuse us for sticking with our beliefs.​

When Bluetooth can do uncompressed transmission, then we’ll talk again. Until then, we’ll stay on the side of maximum quality.

But, back to Hel 2. Here we are, with a device that works with almost every kind of sound I/O out there (save Microsoft Xbox, yeah, talk to them, Sony does UAC1, why can’t they support this ancient standard too—or, say, UAC2?) and outputs excellent sound and has a near-podcast-quality microphone input.

Now, with Hel 2, you have one device that does pretty much anything you need.

• Just want a great-sounding USB DAC/amp? Sure, no problem. Plug it into any computing device and you’re set. Heck, if it doesn’t support UAC2, you still have UAC1 with automatic switching. So it really does do pretty much anything.
• Want something you can use with your phone or iDevice? Sure, same thing, it won’t trigger the “Draws too much power” error (it uses a separate USB wall supply.)
• Or do you want better game sound and communications? Now you can do many consoles as well as PCs and Macs.
• Or how about for Zoom meetings? Yep, the mic input has you covered.
• Eying that optical output on your smart TV? Hel 2 is just the thing for late-light viewing.

Oh, and by the way, Hel 2 is quieter, higher performance, and has more power than the original, in addition to all of the above.

So yeah. Hel to Hel 2 is a hell of a transformation.


An Inauspicious Beginning

Or, in more blunt terms, development of Hel 2 started on the trash heap.

I mean, yeah, we knew that it would be good to have console connectivity and USB-C connectors, but that wasn’t really enough to get development started. What kicked everything off was a new C-Media USB receiver…one that Dave and Mike started designing into new products, but ultimately decided to make everything Unison USB™.

And that’s how the CM6635 made its way into Hel 2—I found it, lonely and disused, in Dave’s abandoned prototypes. Most prototypes we do are simply scrapped at the end of development (some go to the Schiitr, to sit on shelves and confuse people, but most are shredded), so I was literally getting the part out of the bin.

Now, the CM6635, on the face of it, is a very good part. It does the same thing Unison USB does—and a lot more. It also interfaces with an ADC (analog to digital converter) so you can have a microphone input. And it also does SPDIF input as well (as in, optical digital input). And it’s smaller than the old CM6631 we used to use, it doesn’t require external memory, it uses less power to run, and it costs a bit less.

So, win, win, win, right?

Well yes…but we still think Unison USB is better. Unison USB does one thing, and one thing only: receives PCM digital audio over USB. It throws huge computing power at this task (the 32-bit microprocessor we use is almost laughably overpowered). And that’s it. No microphone input. No SPDIF.

Aside: could we add those functions to Unison USB? I wish I could attach an audio file of Dave and Mikes’ laughter when I asked them that exact question. In short, yes we could, but they have more interesting things to do…and they don’t want to take away from Unison USB’s performance in its singleminded task.​

But for a device like Hel 2, the CM6635 was perfect. When we started development of Hel 2, one of the key things was to add an optical input for consoles (this is before Sony started disappearing them). The integrated SPDIF receiver was perfect for that. The fact that it used less power and less real estate was helpful in optimizing the new layout, and the integrated ADC functionality was something we were used to implementing from C-Media in the CM6631A for Hel.

So out went the CM6631, in went the CM6635. We swapped the analog input for an optical, and USB-micro connectors for USB-C.

“Wait a sec,” some of you are yelling. “No analog input? How do we listen to our phones/tablets/etc now?”

Well, to be blunt, you use USB (or optical, if you have an astoundingly weird phone).

Hel 2 is now a digital-only device. We think this makes sense, with so many devices losing the 1/8” analog output anyway; it seems like they are really going by the wayside. In talking to our Hel owners, to, we found the vast majority of them didn’t use the “just an amp” function. So the analog input went bye-bye.

At the time we did the first prototype, that was it: new USB interface, new connectors, new optical. We figured that was enough. What could we expect from a brand-new interface?

It turns out, things were pretty seamless. We worked with C-Media to produce firmware specific to our device, and things worked fairly well from the get-go. There were only a couple of glitches, with the main one being that the device reset wasn’t working reliably. You could turn the Hel 2 off and on, and sometimes it wouldn’t be recognized by the computer. This was solved with some additional oversight logic, and then everything was solid.

Well, except for our changes.

The first thing we did was increase the bit depth and sample rate Hel 2 would accept. While we limit Unison USB to 32/192, Hel 2 goes all the way up to 32/384. And, like Hel before it (and like all of our products), Hel 2 has two crystal oscillators, one for each sample rate multiple, for higher performance. And yes, you read that correctly: Hel 2 will accept higher sample rates than our Unison USB products.

Aside: This is what you might call “thumbing our nose at the establishment.” We’re having a bit of fun; please excuse this silliness. It’s not like we added DSD or MQA.​

Aside to the aside: Also, please don’t take this as an imminent increase in Unison USB sample rates. Mike and Dave are pretty much set on Unison USB—it is stable, it is what it is. If you want to lobby them, bring good arguments. I’m just the analog guy.​

Then, just for fun, I wondered if we could increase performance by using the newer OPA1656 op-amps for output (rather than the OPA1688s we had been using). I was stunned when output increased almost 50% (we rate it 20% higher, because we are conservative.) I was further stunned by how much better it sounded when we also used the OPA1656 for the voltage gain stage. So Hel 2 is 100% OPA1656, one of the most advanced ICs in TI’s arsenal, instead of OPA1662/OPA1688 like Hel.

Yet another aside: a happy consequence of using the OPA1656 for the voltage gain stage is that it has much lower input bias current, which means noise when turning the volume knob is eliminated, without having to go to capacitor-coupling. Hel 2, like Hel, is DC-coupled, no capacitors in the signal path.​

And that, as they say, appeared to be that.

I did one other prototype to optimize the grounds, then got ready to send it to production.

But that’s right around the time Sony kervorked the optical input on the PS5. So the optical input we added started looking pretty silly. For a while, I really worried about it, until Tyler commented, “Well, all smart TVs have optical outputs.”

Huh!

He was totally right! Now we had a device you could plug into a smart TV…which might be a conduit to a game console that didn’t work with optical.

But I realized that was only half the equation. Even if you plugged into your smart TV via optical, you still couldn’t use a microphone input. So that wasn’t perfect.

But…I remembered that the CM6635 could be set as a UAC1 or UAC2 device. As in, you could tell it to be UAC1 for compatibility with older computers and consoles, or you could tell it to be UAC2 for higher bit rates and depths on modern devices.

Could it be set up to detect UAC1/2 capability and autoswitch?

Oh boy, if it could do that, we’d really be set. That would give us PS4 and Switch (and, it was rumored, PS5). We’d just have to look into Microsoft’s requirements and maybe we could get everything…

Long story short, yes, autoswitching UAC1/2 was fairly easy (well, there were some firmware revs after the first candidate, and yes, we had to get a PS5 to confirm it worked on the console, but we got through it. Soon we had a Hel 2 that could be plugged into consoles, TVs, PCs, tablets, and phones…a very big deal, as I mentioned.

So were we done?

Uh, not so fast.


The Big Oops

So, here’s a fun fact: USB-C is complicated.

As in, there are many more levels of complexity to the connector—even if you’re only using it as a connector. I mean, you can go crazy with USB-C.

I mean, to start with, it’s designed to deliver up to 100 watts of power—5 amps at 20 volts. Of course, that’s only with negotiation and testing. You actually need a USB-C interface IC to do the negotiation—“Hey mr power supply, how much power can you safely deliver,” stuff like that. Which is comforting when you’re thinking about passing that much power over a really small wire. Especially one with up to 24 active connections at the plug end.

And it gets weirder, because the superspeed differential pairs are only used when you’re running USB 3.0 protocols and above…the old data connections used for USB 2.0 and below are completely disregarded. Of course, that will take a specific receiver, with its own negotiation, to make that happen as well.

Aside: there is no USB Audio 3.0 or USB Audio Class 3. Period. USB Audio Classes stop at 2. As in, UAC2 is the standard for “fast” audio transmission. And fast is relative. Audio doesn’t need USB 3.0+ speeds. It’s perfectly fine with USB 2.0 speeds. Yes, even stuff like 16x DSD. ​

And USB-C gets even more weirder, because, you know, those 24 connections I mentioned? There are actually 12 pairs, so you can flip over the USB-C cable and use it in either orientation. The pairs mean that one of the connections is always correct. But adding to the confusion is that you can also buy USB-C jacks that don’t have the superspeed connections, or didn’t have data at all and are intended for charging.

But when we started on Hel 2, I figured we didn’t really need to mess with the deep weirdness of USB-C. As in, we didn’t need any power negotiation, because we didn’t need more than the 2A or so a USB-A charger provides. We didn’t need speed negotiation, because we weren’t using the superspeed stuff. We didn’t need to worry about weird connectors, because we were using a standard 24-connection model. And, mechanically we were fine, because everything was paired and it would always be the right connection on one side.

Wellllllllllll…except USB-C got even weirder than we thought, and also requires some resistors so that the interface can tell which way the cable is oriented.

Which didn’t get put on.

Aside: nor did they get put on the Urd prototypes, a fact that I delivered to Dave’s chagrin.​

And…we didn’t catch this until very late in the game. As in, first article late. Nor did any of our early testers catch this. Why? Because when you’re coming from USB-A, orientation doesn’t matter. When you’re doing USB-C to C, though, you need the resistors.

So, when we found that our new Macbook Airs only worked with Hel when the connectors were oriented in one direction, that was an oh schiit moment.

And that’s why Hel 2 is a little late. We needed to add the resistors and check that everything worked fine.

And it does.

Oh, and Urd is fixed as well.

Yeah, do USB-C, they said. It would be easy, I thought.

Well, not so much.

But here we are! I really hope you enjoy the second circle…Hel 2!


Coda: The Other Big Oops

Okay, so I’ve told you before that I write these chapters in advance…sometimes far in advance. The reality was that Hel 2 was supposed to be 2020 product. So I got this knocked out early. (Really early, it turned out, after you take into account adding the UAC1/2 thing and the USB-C big oops.)

And then, just as I get this done, there’s the AKM fire.

“So what?” you might ask. “What does this have to do with Hel 2?”

Well, other than the fact that Hel 2 uses an AKM DAC…and an AKM ADC…and that the programming of the CM6635 is absolutely critical to making those chips run right…and that that programming needs to be different for any other brand of DAC and ADC…

You get the picture. We just designed a product specifically for ICs that had a very, very uncertain future.

Aside: as of this writing, AKM has not confirmed if they will continue making the ADC we use, and there is no date scheduled for the availability of the AK4490 DAC.​

So what do we do?

Two things:

1. Proceed with Hel 2 as designed, leaning on our (large) stock of AKM parts.
2. Get ready for a transition to another DAC and ADC in the future.

As of today, #1 is off and running, and we’re ready for #2. There is a Hel 2 running with a different ADC and DAC, ready to take over when our AKM stock runs out. When exactly that will be, I don’t know. Heck, I don’t even know if we should make a big deal about it (name it “Hel 2x,” where the “x” stands for “oh schiit never eXpected this!”) or if we should just roll it in as a running change. I know people hate running changes, so I figure we’ll call it out, but we’ll see.

In the meantime, as above, we have Hel 2 with AKM right now. Until we’re short on AKM. And that’s all I know right now. I really hope you enjoy it!

 

[golfbravobravo]

I realize it's an old phrase. I was concerned you were self-censoring for fear of offending someone with coarse language L3000. As long as you spell it properly, it's OK to post Schiit on this thread.

I am renowned both for my self-censorship and for my political correctness

Thanks as well!

 

[Pietro Cozzi Tinin]

A highly unreliable source tells me that the 2022 Ford Ecosport is getting and an automotive version of Klipsch KHorn speakers and Pass First Watt amp.

You're right.
It also has the optional caravan like hanger with a nuclear power source to feed it.

 

[golfbravobravo]

I don't plan on replacing mine until post 2030 but I doubt the Golf platform will be electric for the next 6-7 years, they just went to Mark 8 in 2020 model year, so fair few years left in the model series.

The Golf has been electric for some years. You just can't get it in most places......

 

[Pietro Cozzi Tinin]

I use Propane becuase there is no reticulated natural gas where I live, so have 2 x 45kg tanks out the back of the house feeding the stovetop. Not owned, pay an annual "rental" fee that includes delivery of replacement tanks, and then the cost of the gas.

Big pro for this is the higher burning temp of that gas.
Cooking gets better with it.

 

[KoshNaranek]

2021, Chapter 4
The Second Circle

What is the second circle of Hell? As I write this, I’m away from the internet, so I can’t cheat and look it up. But I’m sure someone knows it. And I’m sure it’s not good. Which is very much unlike our Hel 2. Because this is a heckuva sequel. Definitely Aliens vs Alien, if you know what I mean.

“Already?” someone asks. “Didn’t you just introduce Hel, like, 10 minutes ago or something like that?”

To answer that question, Yes, and no.

Yes, Hel 2 is here already. And, to be precise, we introduced the original Hel something like 17 months ago. Which is a short lifespan, we admit.

Aside: Hel is the shortest-lived product ever at Schiit. ​

But the original Hel’s lifespan wasn’t short because it was a bad product…it was short, because we learned quickly how to make it much, much better. So we did. Simple as that.



Early Grumblings

While the reviews of Hel were mainly positive, most people complained about one of two things:

• No console connectivity—as in, no optical or UAC1 capability. We thought this was fine, because we’d envisioned it as a PC gaming device. And because it found another life in the office—lots of home and remote office workers picked up a Hel. Still, they were right…better to have it and not need it, and all that.
• USB-Micro connectors—as in, these were perceived as old…and, to be frank, a pain in the rear end. Problem was, when we did the original Hel design, USB-C connectors were still painfully expensive. Now, they’ve reached the realm of sanity.

So, Hel 2 is a Hel with optical input, UAC1/2 autoswitching, and USB-C connectors.

But that’s really, really underselling it.

And, it’s not the whole story.


The Transformation

Here’s the deal: even if Hel 2 was only those three changes, that’s a huge thing. It transforms Hel from a neat, great-sounding, PC-only gaming rig (or home office rig) to a neat, great-sounding, one-box, two-way communications system you can use with PCs and Macs and many consoles (PS4, PS5, Switch) and virtually any smart TV and monitors with optical output.

Stop. Go back. Read that again.

Or use this simple bulleted comparison:

• Hel: PCs and Macs (and, yeah, iOS and Android and Linux)
• Hel 2: PCs and Macs and consoles and smart TVs and monitors (and, yeah, iOS and Android and Linux)

Yes.

This is a HUGE deal.

“Well, what about Brutoof and stuff like that,” someone is gonna ask. “I likes my wirelesses!”

That’s cool. We get it. But Bluetooth won’t match the quality of a wired connection. Period.

No. Go back and read that again, too. Bluetooth mangles everything that passes through it. Got Qobuz for its lossless? Well, it’s no longer lossless when it goes through your hyper-convenient Bluetooth connection. Got high-res albums you bought at great expense? Yeah, into the blender they go, never to be the same again.

Yes, the mangling is less these days, what with AptX and AptX HD and LDAC and whatever else is new in the world of proprietary CODECs by the time I write this, which probably gives you a good idea of another reason why we don’t want to get into the Bluetooth morass—between different protocol revision levels and proprietary codecs and intentional-transmitter FCC certification, on top of the compression jiggery-pokery, we decided “we gots better things to do, folks!”

Aside: and yes, I know, this isn’t going to be a decision that’s popular with everyone, or understood by everyone, but it’s what we do. Please excuse us for sticking with our beliefs.​

When Bluetooth can do uncompressed transmission, then we’ll talk again. Until then, we’ll stay on the side of maximum quality.

But, back to Hel 2. Here we are, with a device that works with almost every kind of sound I/O out there (save Microsoft Xbox, yeah, talk to them, Sony does UAC1, why can’t they support this ancient standard too—or, say, UAC2?) and outputs excellent sound and has a near-podcast-quality microphone input.

Now, with Hel 2, you have one device that does pretty much anything you need.

• Just want a great-sounding USB DAC/amp? Sure, no problem. Plug it into any computing device and you’re set. Heck, if it doesn’t support UAC2, you still have UAC1 with automatic switching. So it really does do pretty much anything.
• Want something you can use with your phone or iDevice? Sure, same thing, it won’t trigger the “Draws too much power” error (it uses a separate USB wall supply.)
• Or do you want better game sound and communications? Now you can do many consoles as well as PCs and Macs.
• Or how about for Zoom meetings? Yep, the mic input has you covered.
• Eying that optical output on your smart TV? Hel 2 is just the thing for late-light viewing.

Oh, and by the way, Hel 2 is quieter, higher performance, and has more power than the original, in addition to all of the above.

So yeah. Hel to Hel 2 is a hell of a transformation.


An Inauspicious Beginning

Or, in more blunt terms, development of Hel 2 started on the trash heap.

I mean, yeah, we knew that it would be good to have console connectivity and USB-C connectors, but that wasn’t really enough to get development started. What kicked everything off was a new C-Media USB receiver…one that Dave and Mike started designing into new products, but ultimately decided to make everything Unison USB™.

And that’s how the CM6635 made its way into Hel 2—I found it, lonely and disused, in Dave’s abandoned prototypes. Most prototypes we do are simply scrapped at the end of development (some go to the Schiitr, to sit on shelves and confuse people, but most are shredded), so I was literally getting the part out of the bin.

Now, the CM6635, on the face of it, is a very good part. It does the same thing Unison USB does—and a lot more. It also interfaces with an ADC (analog to digital converter) so you can have a microphone input. And it also does SPDIF input as well (as in, optical digital input). And it’s smaller than the old CM6631 we used to use, it doesn’t require external memory, it uses less power to run, and it costs a bit less.

So, win, win, win, right?

Well yes…but we still think Unison USB is better. Unison USB does one thing, and one thing only: receives PCM digital audio over USB. It throws huge computing power at this task (the 32-bit microprocessor we use is almost laughably overpowered). And that’s it. No microphone input. No SPDIF.

Aside: could we add those functions to Unison USB? I wish I could attach an audio file of Dave and Mikes’ laughter when I asked them that exact question. In short, yes we could, but they have more interesting things to do…and they don’t want to take away from Unison USB’s performance in its singleminded task.

But for a device like Hel 2, the CM6635 was perfect. When we started development of Hel 2, one of the key things was to add an optical input for consoles (this is before Sony started disappearing them). The integrated SPDIF receiver was perfect for that. The fact that it used less power and less real estate was helpful in optimizing the new layout, and the integrated ADC functionality was something we were used to implementing from C-Media in the CM6631A for Hel.

So out went the CM6631, in went the CM6635. We swapped the analog input for an optical, and USB-micro connectors for USB-C.

“Wait a sec,” some of you are yelling. “No optical input? How do we listen to our phones/tablets/etc now?”

Well, to be blunt, you use USB (or optical, if you have an astoundingly weird phone).

Hel 2 is now a digital-only device. We think this makes sense, with so many devices losing the 1/8” analog output anyway; it seems like they are really going by the wayside. In talking to our Hel owners, to, we found the vast majority of them didn’t use the “just an amp” function. So the analog input went bye-bye.

At the time we did the first prototype, that was it: new USB interface, new connectors, new optical. We figured that was enough. What could we expect from a brand-new interface?

It turns out, things were pretty seamless. We worked with C-Media to produce firmware specific to our device, and things worked fairly well from the get-go. There were only a couple of glitches, with the main one being that the device reset wasn’t working reliably. You could turn the Hel 2 off and on, and sometimes it wouldn’t be recognized by the computer. This was solved with some additional oversight logic, and then everything was solid.

Well, except for our changes.

The first thing we did was increase the bit depth and sample rate Hel 2 would accept. While we limit Unison USB to 32/192, Hel 2 goes all the way up to 32/384. And, like Hel before it (and like all of our products), Hel 2 has two crystal oscillators, one for each sample rate multiple, for higher performance. And yes, you read that correctly: Hel 2 will accept higher sample rates than our Unison USB products.

Aside: This is what you might call “thumbing our nose at the establishment.” We’re having a bit of fun; please excuse this silliness. It’s not like we added DSD or MQA.​

Aside to the aside: Also, please don’t take this as an imminent increase in Unison USB sample rates. Mike and Dave are pretty much set on Unison USB—it is stable, it is what it is. If you want to lobby them, bring good arguments. I’m just the analog guy.​

Then, just for fun, I wondered if we could increase performance by using the newer OPA1656 op-amps for output (rather than the OPA1688s we had been using). I was stunned when output increased almost 50% (we rate it 20% higher, because we are conservative.) I was further stunned by how much better it sounded when we also used the OPA1656 for the voltage gain stage. So Hel 2 is 100% OPA1656, one of the most advanced ICs in TI’s arsenal, instead of OPA1662/OPA1688 like Hel.

Yet another aside: a happy consequence of using the OPA1656 for the voltage gain stage is that it has much lower input bias current, which means noise when turning the volume knob is eliminated, without having to go to capacitor-coupling. Hel 2, like Hel, is DC-coupled, no capacitors in the signal path.

And that, as they say, appeared to be that.

I did one other prototype to optimize the grounds, then got ready to send it to production.

But that’s right around the time Sony kervorked the optical input on the PS5. So the optical input we added started looking pretty silly. For a while, I really worried about it, until Tyler commented, “Well, all smart TVs have optical outputs.”

Huh!

He was totally right! Now we had a device you could plug into a smart TV…which might be a conduit to a game console that didn’t work with optical.

But I realized that was only half the equation. Even if you plugged into your smart TV via optical, you still couldn’t use a microphone input. So that wasn’t perfect.

But…I remembered that the CM6635 could be set as a UAC1 or UAC2 device. As in, you could tell it to be UAC1 for compatibility with older computers and consoles, or you could tell it to be UAC2 for higher bit rates and depths on modern devices.

Could it be set up to detect UAC1/2 capability and autoswitch?

Oh boy, if it could do that, we’d really be set. That would give us PS4 and Switch (and, it was rumored, PS5). We’d just have to look into Microsoft’s requirements and maybe we could get everything…

Long story short, yes, autoswitching UAC1/2 was fairly easy (well, there were some firmware revs after the first candidate, and yes, we had to get a PS5 to confirm it worked on the console, but we got through it. Soon we had a Hel 2 that could be plugged into consoles, TVs, PCs, tablets, and phones…a very big deal, as I mentioned.

So were we done?

Uh, not so fast.


The Big Oops

So, here’s a fun fact: USB-C is complicated.

As in, there are many more levels of complexity to the connector—even if you’re only using it as a connector. I mean, you can go crazy with USB-C.

I mean, to start with, it’s designed to deliver up to 100 watts of power—5 amps at 20 volts. Of course, that’s only with negotiation and testing. You actually need a USB-C interface IC to do the negotiation—“Hey mr power supply, how much power can you safely deliver,” stuff like that. Which is comforting when you’re thinking about passing that much power over a really small wire. Especially one with up to 24 active connections at the plug end.

And it gets weirder, because the superspeed differential pairs are only used when you’re running USB 3.0 protocols and above…the old data connections used for USB 2.0 and below are completely disregarded. Of course, that will take a specific receiver, with its own negotiation, to make that happen as well.

Aside: there is no USB Audio 3.0 or USB Audio Class 3. Period. USB Audio Classes stop at 2. As in, UAC2 is the standard for “fast” audio transmission. And fast is relative. Audio doesn’t need USB 3.0+ speeds. It’s perfectly fine with USB 2.0 speeds. Yes, even stuff like 16x DSD. ​

And USB-C gets even more weirder, because, you know, those 24 connections I mentioned? There are actually 12 pairs, so you can flip over the USB-C cable and use it in either orientation. The pairs mean that one of the connections is always correct. But adding to the confusion is that you can also buy USB-C jacks that don’t have the superspeed connections, or didn’t have data at all and are intended for charging.

But when we started on Hel 2, I figured we didn’t really need to mess with the deep weirdness of USB-C. As in, we didn’t need any power negotiation, because we didn’t need more than the 2A or so a USB-A charger provides. We didn’t need speed negotiation, because we weren’t using the superspeed stuff. We didn’t need to worry about weird connectors, because we were using a standard 24-connection model. And, mechanically we were fine, because everything was paired and it would always be the right connection on one side.

Wellllllllllll…except USB-C got even weirder than we thought, and also requires some resistors so that the interface can tell which way the cable is oriented.
Which didn’t get put on.

Aside: nor did they get put on the Urd prototypes, a fact that I delivered to Dave’s chagrin.​

And…we didn’t catch this until very late in the game. As in, first article late. Nor did any of our early testers catch this. Why? Because when you’re coming from USB-A, orientation doesn’t matter. When you’re doing USB-C to C, though, you need the resistors.

So, when we found that our new Macbook Airs only worked with Hel when the connectors were oriented in one direction, that was an oh schiit moment.

And that’s why Hel 2 is a little late. We needed to add the resistors and check that everything worked fine.

And it does.

Oh, and Urd is fixed as well.

Yeah, do USB-C, they said. It would be easy, I thought.

Well, not so much.

But here we are! I really hope you enjoy the second circle…Hel 2!


Coda: The Other Big Oops

Okay, so I’ve told you before that I write these chapters in advance…sometimes far in advance. The reality was that Hel 2 was supposed to be 2020 product. So I got this knocked out early. (Really early, it turned out, after you take into account adding the UAC1/2 thing and the USB-C big oops.)

And then, just as I get this done, there’s the AKM fire.

“So what?” you might ask. “What does this have to do with Hel 2?”

Well, other than the fact that Hel 2 uses an AKM DAC…and an AKM ADC…and that the programming of the CM6635 is absolutely critical to making those chips run right…and that that programming needs to be different for any other brand of DAC and ADC…

You get the picture. We just designed a product specifically for ICs that had a very, very uncertain future.

Aside: as of this writing, AKM has not confirmed if they will continue making the ADC we use, and there is no date scheduled for the availability of the AK4490 DAC.​

So what do we do?

Two things:

1. Proceed with Hel 2 as designed, leaning on our (large) stock of AKM parts.
2. Get ready for a transition to another DAC and ADC in the future.

As of today, #1 is off and running, and we’re ready for #2. There is a Hel 2 running with a different ADC and DAC, ready to take over when our AKM stock runs out. When exactly that will be, I don’t know. Heck, I don’t even know if we should make a big deal about it (name it “Hel 2x,” where the “x” stands for “oh schiit never eXpected this!”) or if we should just roll it in as a running change. I know people hate running changes, so I figure we’ll call it out, but we’ll see.

In the meantime, as above, we have Hel 2 with AKM right now. Until we’re short on AKM. And that’s all I know right now. I really hope you enjoy it!

Thank you for another enjoyable read Jason.

Thank you also for calling Bluetooth audio for what it is: Carp

 

[Balthazar B]

2021, Chapter 4
The Second Circle

What is the second circle of Hell? As I write this, I’m away from the internet, so I can’t cheat and look it up. But I’m sure someone knows it. And I’m sure it’s not good. Which is very much unlike our Hel 2. Because this is a heckuva sequel. Definitely Aliens vs Alien, if you know what I mean.

For your edification, dear sir.



As Woody Allen said, "Sex without love is a meaningless experience. But as far as meaningless experiences go, it's pretty damn good."

 

[dieslemat]

2021, Chapter 4
The Second Circle

What is the second circle of Hell? As I write this, I’m away from the internet, so I can’t cheat and look it up. But I’m sure someone knows it. And I’m sure it’s not good. Which is very much unlike our Hel 2. Because this is a heckuva sequel. Definitely Aliens vs Alien, if you know what I mean.

“Already?” someone asks. “Didn’t you just introduce Hel, like, 10 minutes ago or something like that?”

To answer that question, Yes, and no.

Yes, Hel 2 is here already. And, to be precise, we introduced the original Hel something like 17 months ago. Which is a short lifespan, we admit.

Aside: Hel is the shortest-lived product ever at Schiit. ​

But the original Hel’s lifespan wasn’t short because it was a bad product…it was short, because we learned quickly how to make it much, much better. So we did. Simple as that.



Early Grumblings

While the reviews of Hel were mainly positive, most people complained about one of two things:

• No console connectivity—as in, no optical or UAC1 capability. We thought this was fine, because we’d envisioned it as a PC gaming device. And because it found another life in the office—lots of home and remote office workers picked up a Hel. Still, they were right…better to have it and not need it, and all that.
• USB-Micro connectors—as in, these were perceived as old…and, to be frank, a pain in the rear end. Problem was, when we did the original Hel design, USB-C connectors were still painfully expensive. Now, they’ve reached the realm of sanity.

So, Hel 2 is a Hel with optical input, UAC1/2 autoswitching, and USB-C connectors.

But that’s really, really underselling it.

And, it’s not the whole story.


The Transformation

Here’s the deal: even if Hel 2 was only those three changes, that’s a huge thing. It transforms Hel from a neat, great-sounding, PC-only gaming rig (or home office rig) to a neat, great-sounding, one-box, two-way communications system you can use with PCs and Macs and many consoles (PS4, PS5, Switch) and virtually any smart TV and monitors with optical output.

Stop. Go back. Read that again.

Or use this simple bulleted comparison:

• Hel: PCs and Macs (and, yeah, iOS and Android and Linux)
• Hel 2: PCs and Macs and consoles and smart TVs and monitors (and, yeah, iOS and Android and Linux)

Yes.

This is a HUGE deal.

“Well, what about Brutoof and stuff like that,” someone is gonna ask. “I likes my wirelesses!”

That’s cool. We get it. But Bluetooth won’t match the quality of a wired connection. Period.

No. Go back and read that again, too. Bluetooth mangles everything that passes through it. Got Qobuz for its lossless? Well, it’s no longer lossless when it goes through your hyper-convenient Bluetooth connection. Got high-res albums you bought at great expense? Yeah, into the blender they go, never to be the same again.

Yes, the mangling is less these days, what with AptX and AptX HD and LDAC and whatever else is new in the world of proprietary CODECs by the time I write this, which probably gives you a good idea of another reason why we don’t want to get into the Bluetooth morass—between different protocol revision levels and proprietary codecs and intentional-transmitter FCC certification, on top of the compression jiggery-pokery, we decided “we gots better things to do, folks!”

Aside: and yes, I know, this isn’t going to be a decision that’s popular with everyone, or understood by everyone, but it’s what we do. Please excuse us for sticking with our beliefs.​

When Bluetooth can do uncompressed transmission, then we’ll talk again. Until then, we’ll stay on the side of maximum quality.

But, back to Hel 2. Here we are, with a device that works with almost every kind of sound I/O out there (save Microsoft Xbox, yeah, talk to them, Sony does UAC1, why can’t they support this ancient standard too—or, say, UAC2?) and outputs excellent sound and has a near-podcast-quality microphone input.

Now, with Hel 2, you have one device that does pretty much anything you need.

• Just want a great-sounding USB DAC/amp? Sure, no problem. Plug it into any computing device and you’re set. Heck, if it doesn’t support UAC2, you still have UAC1 with automatic switching. So it really does do pretty much anything.
• Want something you can use with your phone or iDevice? Sure, same thing, it won’t trigger the “Draws too much power” error (it uses a separate USB wall supply.)
• Or do you want better game sound and communications? Now you can do many consoles as well as PCs and Macs.
• Or how about for Zoom meetings? Yep, the mic input has you covered.
• Eying that optical output on your smart TV? Hel 2 is just the thing for late-light viewing.

Oh, and by the way, Hel 2 is quieter, higher performance, and has more power than the original, in addition to all of the above.

So yeah. Hel to Hel 2 is a hell of a transformation.


An Inauspicious Beginning

Or, in more blunt terms, development of Hel 2 started on the trash heap.

I mean, yeah, we knew that it would be good to have console connectivity and USB-C connectors, but that wasn’t really enough to get development started. What kicked everything off was a new C-Media USB receiver…one that Dave and Mike started designing into new products, but ultimately decided to make everything Unison USB™.

And that’s how the CM6635 made its way into Hel 2—I found it, lonely and disused, in Dave’s abandoned prototypes. Most prototypes we do are simply scrapped at the end of development (some go to the Schiitr, to sit on shelves and confuse people, but most are shredded), so I was literally getting the part out of the bin.

Now, the CM6635, on the face of it, is a very good part. It does the same thing Unison USB does—and a lot more. It also interfaces with an ADC (analog to digital converter) so you can have a microphone input. And it also does SPDIF input as well (as in, optical digital input). And it’s smaller than the old CM6631 we used to use, it doesn’t require external memory, it uses less power to run, and it costs a bit less.

So, win, win, win, right?

Well yes…but we still think Unison USB is better. Unison USB does one thing, and one thing only: receives PCM digital audio over USB. It throws huge computing power at this task (the 32-bit microprocessor we use is almost laughably overpowered). And that’s it. No microphone input. No SPDIF.

Aside: could we add those functions to Unison USB? I wish I could attach an audio file of Dave and Mikes’ laughter when I asked them that exact question. In short, yes we could, but they have more interesting things to do…and they don’t want to take away from Unison USB’s performance in its singleminded task.

But for a device like Hel 2, the CM6635 was perfect. When we started development of Hel 2, one of the key things was to add an optical input for consoles (this is before Sony started disappearing them). The integrated SPDIF receiver was perfect for that. The fact that it used less power and less real estate was helpful in optimizing the new layout, and the integrated ADC functionality was something we were used to implementing from C-Media in the CM6631A for Hel.

So out went the CM6631, in went the CM6635. We swapped the analog input for an optical, and USB-micro connectors for USB-C.

“Wait a sec,” some of you are yelling. “No optical input? How do we listen to our phones/tablets/etc now?”

Well, to be blunt, you use USB (or optical, if you have an astoundingly weird phone).

Hel 2 is now a digital-only device. We think this makes sense, with so many devices losing the 1/8” analog output anyway; it seems like they are really going by the wayside. In talking to our Hel owners, to, we found the vast majority of them didn’t use the “just an amp” function. So the analog input went bye-bye.

At the time we did the first prototype, that was it: new USB interface, new connectors, new optical. We figured that was enough. What could we expect from a brand-new interface?

It turns out, things were pretty seamless. We worked with C-Media to produce firmware specific to our device, and things worked fairly well from the get-go. There were only a couple of glitches, with the main one being that the device reset wasn’t working reliably. You could turn the Hel 2 off and on, and sometimes it wouldn’t be recognized by the computer. This was solved with some additional oversight logic, and then everything was solid.

Well, except for our changes.

The first thing we did was increase the bit depth and sample rate Hel 2 would accept. While we limit Unison USB to 32/192, Hel 2 goes all the way up to 32/384. And, like Hel before it (and like all of our products), Hel 2 has two crystal oscillators, one for each sample rate multiple, for higher performance. And yes, you read that correctly: Hel 2 will accept higher sample rates than our Unison USB products.

Aside: This is what you might call “thumbing our nose at the establishment.” We’re having a bit of fun; please excuse this silliness. It’s not like we added DSD or MQA.​

Aside to the aside: Also, please don’t take this as an imminent increase in Unison USB sample rates. Mike and Dave are pretty much set on Unison USB—it is stable, it is what it is. If you want to lobby them, bring good arguments. I’m just the analog guy.​

Then, just for fun, I wondered if we could increase performance by using the newer OPA1656 op-amps for output (rather than the OPA1688s we had been using). I was stunned when output increased almost 50% (we rate it 20% higher, because we are conservative.) I was further stunned by how much better it sounded when we also used the OPA1656 for the voltage gain stage. So Hel 2 is 100% OPA1656, one of the most advanced ICs in TI’s arsenal, instead of OPA1662/OPA1688 like Hel.

Yet another aside: a happy consequence of using the OPA1656 for the voltage gain stage is that it has much lower input bias current, which means noise when turning the volume knob is eliminated, without having to go to capacitor-coupling. Hel 2, like Hel, is DC-coupled, no capacitors in the signal path.

And that, as they say, appeared to be that.

I did one other prototype to optimize the grounds, then got ready to send it to production.

But that’s right around the time Sony kervorked the optical input on the PS5. So the optical input we added started looking pretty silly. For a while, I really worried about it, until Tyler commented, “Well, all smart TVs have optical outputs.”

Huh!

He was totally right! Now we had a device you could plug into a smart TV…which might be a conduit to a game console that didn’t work with optical.

But I realized that was only half the equation. Even if you plugged into your smart TV via optical, you still couldn’t use a microphone input. So that wasn’t perfect.

But…I remembered that the CM6635 could be set as a UAC1 or UAC2 device. As in, you could tell it to be UAC1 for compatibility with older computers and consoles, or you could tell it to be UAC2 for higher bit rates and depths on modern devices.

Could it be set up to detect UAC1/2 capability and autoswitch?

Oh boy, if it could do that, we’d really be set. That would give us PS4 and Switch (and, it was rumored, PS5). We’d just have to look into Microsoft’s requirements and maybe we could get everything…

Long story short, yes, autoswitching UAC1/2 was fairly easy (well, there were some firmware revs after the first candidate, and yes, we had to get a PS5 to confirm it worked on the console, but we got through it. Soon we had a Hel 2 that could be plugged into consoles, TVs, PCs, tablets, and phones…a very big deal, as I mentioned.

So were we done?

Uh, not so fast.


The Big Oops

So, here’s a fun fact: USB-C is complicated.

As in, there are many more levels of complexity to the connector—even if you’re only using it as a connector. I mean, you can go crazy with USB-C.

I mean, to start with, it’s designed to deliver up to 100 watts of power—5 amps at 20 volts. Of course, that’s only with negotiation and testing. You actually need a USB-C interface IC to do the negotiation—“Hey mr power supply, how much power can you safely deliver,” stuff like that. Which is comforting when you’re thinking about passing that much power over a really small wire. Especially one with up to 24 active connections at the plug end.

And it gets weirder, because the superspeed differential pairs are only used when you’re running USB 3.0 protocols and above…the old data connections used for USB 2.0 and below are completely disregarded. Of course, that will take a specific receiver, with its own negotiation, to make that happen as well.

Aside: there is no USB Audio 3.0 or USB Audio Class 3. Period. USB Audio Classes stop at 2. As in, UAC2 is the standard for “fast” audio transmission. And fast is relative. Audio doesn’t need USB 3.0+ speeds. It’s perfectly fine with USB 2.0 speeds. Yes, even stuff like 16x DSD. ​

And USB-C gets even more weirder, because, you know, those 24 connections I mentioned? There are actually 12 pairs, so you can flip over the USB-C cable and use it in either orientation. The pairs mean that one of the connections is always correct. But adding to the confusion is that you can also buy USB-C jacks that don’t have the superspeed connections, or didn’t have data at all and are intended for charging.

But when we started on Hel 2, I figured we didn’t really need to mess with the deep weirdness of USB-C. As in, we didn’t need any power negotiation, because we didn’t need more than the 2A or so a USB-A charger provides. We didn’t need speed negotiation, because we weren’t using the superspeed stuff. We didn’t need to worry about weird connectors, because we were using a standard 24-connection model. And, mechanically we were fine, because everything was paired and it would always be the right connection on one side.

Wellllllllllll…except USB-C got even weirder than we thought, and also requires some resistors so that the interface can tell which way the cable is oriented.
Which didn’t get put on.

Aside: nor did they get put on the Urd prototypes, a fact that I delivered to Dave’s chagrin.​

And…we didn’t catch this until very late in the game. As in, first article late. Nor did any of our early testers catch this. Why? Because when you’re coming from USB-A, orientation doesn’t matter. When you’re doing USB-C to C, though, you need the resistors.

So, when we found that our new Macbook Airs only worked with Hel when the connectors were oriented in one direction, that was an oh schiit moment.

And that’s why Hel 2 is a little late. We needed to add the resistors and check that everything worked fine.

And it does.

Oh, and Urd is fixed as well.

Yeah, do USB-C, they said. It would be easy, I thought.

Well, not so much.

But here we are! I really hope you enjoy the second circle…Hel 2!


Coda: The Other Big Oops

Okay, so I’ve told you before that I write these chapters in advance…sometimes far in advance. The reality was that Hel 2 was supposed to be 2020 product. So I got this knocked out early. (Really early, it turned out, after you take into account adding the UAC1/2 thing and the USB-C big oops.)

And then, just as I get this done, there’s the AKM fire.

“So what?” you might ask. “What does this have to do with Hel 2?”

Well, other than the fact that Hel 2 uses an AKM DAC…and an AKM ADC…and that the programming of the CM6635 is absolutely critical to making those chips run right…and that that programming needs to be different for any other brand of DAC and ADC…

You get the picture. We just designed a product specifically for ICs that had a very, very uncertain future.

Aside: as of this writing, AKM has not confirmed if they will continue making the ADC we use, and there is no date scheduled for the availability of the AK4490 DAC.​

So what do we do?

Two things:

1. Proceed with Hel 2 as designed, leaning on our (large) stock of AKM parts.
2. Get ready for a transition to another DAC and ADC in the future.

As of today, #1 is off and running, and we’re ready for #2. There is a Hel 2 running with a different ADC and DAC, ready to take over when our AKM stock runs out. When exactly that will be, I don’t know. Heck, I don’t even know if we should make a big deal about it (name it “Hel 2x,” where the “x” stands for “oh schiit never eXpected this!”) or if we should just roll it in as a running change. I know people hate running changes, so I figure we’ll call it out, but we’ll see.

In the meantime, as above, we have Hel 2 with AKM right now. Until we’re short on AKM. And that’s all I know right now. I really hope you enjoy it!

I hope you have plans to update your photo to a PS4 or PS5

 

[oryan_dunn]

I hope you have plans to update your photo to a PS4 or PS5

Actually, with the addition of Toslink, Hel2 would work with a PS2...

 

[strider1007]

To Hell two it is....

 

[ev666il]

Interesting chapter. It also confirms Urd will come with USB-C, which I didn’t know.

Does that mean we’ll get USB-C Unison boards in future? My expensive aftermarket USB cable hopes not, though I could always ask to have it factory re-terminated...

 

[JoeWhip]

Great article Jason. As for Unison, no need to increase to DXD resolutions until DACs like The Yggy can decode it natively. At least the 8x light is ready,

 

[Randolf711]

Interesting chapter. It also confirms Urd will come with USB-C, which I didn’t know.

Does that mean we’ll get USB-C Unison boards in future? My expensive aftermarket USB cable hopes not, though I could always ask to have it factory re-terminated...

Yeah, I knew it was going accept USB-C (because all new Mac's only have USB-C now) but what I'm not 100% sure about is if the output to DAC will include USB-C. I would assume it will remain USB-A for compatibility with Schiit DACs. So you don't need to throw those cables away yet. The Urd could be the most fascinating Schiit product ever released. It is quite the endeavor considering all it offers.

 

[yonson]

Holy Hel2 I've got to upgrade my Hel...