[JoeWhip]

Trained on punch cards in college. Loved those infinite do loops and the phone modems!

 

[W S L]

2020, Chapter 1:
The Weldenheim Chronicles

“Weldenheim?” you might ask. “What the heck is that?”

Patience. All will be revealed. Sit back, relax, and enjoy a read about one of the most interesting projects I’ve had in a long while—the world’s first and only ribbon headphone amplifier, Jotunheim R.

What’s most fun, perhaps, is that this story starts long before I was aware of the Raal/Requisite headphone. You could almost say the Jotunheim R is a summation of my entire career in audio.

The story starts back in the Sumo days, now almost three decades past.

Sumo was my first real job. Yeah, I had a job working for a government contractor doing communications system stuff, but that’s not a job. It’s a placeholder, a thing that dispenses enough money for you to swerve away from asking the hard questions: why am I here, will this ever mean anything, am I ever going to have any fun?

And Sumo made power amplifiers. Big honkin power amplifiers, amps that could deliver 200 amps of current per channel (on a short term basis, of course). Sumo’s amps used a error correction scheme that allowed us to turn up output current to 11. Really neat stuff. I’ve referred you before to Hawksford and Cordell if you want the theory behind it.

It’s funny how ideas have a way of coming around, a few years or decades later. “Error correction” is now known as “feedforward” and is the pimp du jour.

I may have even been King Pimp of Feedforward Mountain if I’d decided to include it on the original Jotunheim, when I started playing around with it back in 2014 or so. The first prototypes included the Hawksford/Cordell/Sumo error correction scheme. I pulled it out of the final design at least in part because it could deliver enough current to weld the TRS jack to the plug if you got it into your head to yank the headphones out at the wrong time when it was playing loudly. I could have detuned it a bit to keep the jack and plugs from becoming one, but the complexity, and my own concerns about compensation, kept it out of the final design.

“So what does this all mean, Stoddard?” someone shouts from the audience.

Well, if by “this all,” you mean “all this blathering about old amps and current,” it’s to set the stage. To provide the ambience. To hint at where this is all going.

Because, if you’re talking ribbon headphones, you’re basically talking about driving a near-zero-ohm load. A dead short. A screwdriver.

And if you want to drive something like that, you need a ton of current.


A Bit of Foreshadowing

Now, here’s the thing: long before the Raal/Requisite ribbon headphone was a reality—think, just a couple of years after Schiit started up—I had a meeting with another headphone company, and they mentioned they were working on a ribbon headphone.

“But of course there are a lot of technical challenges,” they told me. “The main one being that the ribbon is almost a dead short.”

I knew ribbon tweeters frequently used transformers to bring their impedance in-line with that of a typical speaker driver. “I expect transformers are too heavy for headphones.”

They nodded. “So we’d have to develop an amplifier specifically for driving these headphones.”

“Which makes it like an electrostatic,” I said.

“Yeah, so now it’s a system. So we’d have to sell a headphone and an amp. And the amp design itself is a challenge.”

I frowned. “Not really, I’ve done some really, really high current amps in the past. I don’t think it’d be too hard.”

They looked at me doubtfully. “It’s nearly a dead short.”

“And Sumo amps used to do 50-200A into 0.1 ohms on a burst basis.”

Now I had their attention. But from all the side-glances and sighs, I quickly figured this was something they were just playing with, maybe to keep the interest of a fickle designer-type in their company. Still, I let them know that if they wanted to do a wacky high-current amp, I was up for it.

Because, after all, it was a great challenge. It’s not often you get an audio engineering job that’s so far outside the norm…and so different than anything else. Electrostats were outside the norm, sure, but there were plenty of stat amps out there. Super hard-to-drive headphones like the HE-6 were outside the norm, too, but there were a growing number of super-stout headphone amps at the time, and plenty of speaker amps to use. Doing something for a wacky ribbon headphone would be a ton of fun.

But, after we parted, the weeks rolled past, and nobody contacted me about a ribbon amp. I wasn’t particularly surprised.

Ah well, no worries, plenty of other stuff to do…


Enter Someone Crazy Enough to Do It

I first became aware of the Raal/Requisite headphones the way I find out about many new things these days—I read about them on a forum.

At first, I didn’t really know what they were. They appeared about the same time the MySphere products showed up, so I remembered thinking, “Ah yeah, more K1000 type stuff,” lumping them together, and forgetting about them.

For a while.

I think someone told me more about the Raals at some point, and it sank in that they were ribbon headphones. But this was the middle of a crazy engineering time at Schiit, so, for some reason, it didn’t really register that these were ribbon headphones, and it didn’t occur to me to ask what the heck these guys were doing to drive them.

Until Danny from Requisite visited the Schiitr sometime in early June, 2019.

Danny was looking for an amp to run his headphones—or, more specifically, an amp to run the impedance converter box that ran the Raal/Requisite ribbon headphones. Eddie took care of him, and Danny was impressed by the capabilities of Vidar.

A few days later, Danny sent an introduction email to Mike and I, asking if he could get Vidars, in black finish, possibly to sell with his headphones. At the time, I was in the middle of engineering work beyond imagining (all the normal stuff that goes sideways around a product launch, plus CanJam LA coming up, plus stuff we were still working on and was late…I mean, heck, remember, we introduced 13 products last year), and I sent him an email back that said something like:

Holy crap busy!
Talk to Denise she will help!
Ten thousand too many things!
(But yeah let’s talk when it gets a little less crazy.)

Jason​

Denise got Danny his Vidars for the LA CanJam, so that might have been that. Heck, I could have stepped back and said, “Sure, please buy Vidars,” and call it done. I mean, that’s what Danny wanted, and he would be perfectly happy doing that.

But it had sunk in: this was a ribbon headphone.

And I also remembered: people didn’t ask for cars, they asked for faster horses.

As in, until the automobile all they could imagine was a faster horse. Before the personal computer, all they could imagine was a larger TV. Before the iPhone, all they could imagine was a better phone keyboard.

So I made it a point to go to the LA CanJam, and to stop by the Raal/Requisite booth. Danny was there, with a Vidar, as well as a couple of other amps that sell for much more than a Vidar. He was playing the headphones, and allowing people to A/B the amps.

He was also telling people how much he liked the Vidar, and what a great value it was. He may even have mentioned it sounded better than at least one of the other, more expensive amps (or maybe I hallucinated that…we’ll never know).

But…he clearly liked the amp, and he was happily telling people how good it was. At that moment, I turned to Denise and said, “Get him as many Vidars as he wants.”

But I still hadn’t heard the headphones.

Now, I’ve heard a ton of headphones. Tons. Dynamics and planars and stats and open and closed and semi open and high efficiency and low efficiency and high impedance and low impedance and bright and dark and brash and slow…no, I’m not bragging, this is my job. The point is, I’d heard so many headphones that I thought I had a pretty good grasp of the breadth and depth of how they could sound.

When Danny handed me the Raal/Requisite headphones, I looked at them a bit skeptically. The ribbons are protected by sharp post-modern crescents of stainless steel, and the whole assembly is bolted to angular, articulating carbon fiber wings that look like pieces of Darth Vader’s TIE fighter. I was kinda-sorta afraid I was going to deli-slice my ears when I put them on.

Danny saw my hesitation. “They’re actually really comfortable. Just put the pads near your ears, and adjust the flaps in for more bass, out for less. Leaving them open about like they are is the most natural sound.”

Well, heck, it couldn’t hurt too much, could it?

I put them on. They didn’t fit very tight, but, as Danny said, they were comfortable. I pushed them back on my head as instructed and Danny lit up some tunes.

Ho.

Lee.

Schiit.

Seriously, this was completely unlike anything I’d ever heard before, and completely different than what I expected. Even on the loud-ass show floor, the Raal/Requisite headphones were the most dynamic, transparent headphones I’d ever heard. Furthermore, they didn’t sound anemic or thin, like I’d expected from the open-baffle design. They had bass. Maybe not a ton of sub-bass, but it sounded, well…shockingly realistic.

Danny saw the look on my face and grinned. “So…yeah?”

“Yeah,” I said.

Eventually I took them off. “We need a pair of these.”

“Can do,” Danny said. “In fact, can I come back to the Schiitr and have a listen to some other gear when I drop them off? I want to try some DACs and preamps to go with the Vidar.”

Oh you want even more gear? I almost laughed.

“Of course. I’ll see you there.

And that’s what started it all. Just one email, a quick listen, and an agreement to meet at the Schiitr. I still wasn’t thinking about direct-drive amps. I was just happy to hear a great new headphone, and that the guy behind them liked our gear. Win-win.


The Dumb Protagonist

I could have made it easy.

I could have shut up.

But no. When I have an idea, and it’s the right idea, I’m pretty damn stubborn.

But I’m getting ahead of myself. Let’s rewind to the day when I met Danny at the Schiitr, and he delivered our Raal/Requisite headphones. I figured it was just another meet and greet, but Danny actually had a specific goal in mind: putting together a complete Schiit system for his headphones—not just an amp, but the DAC and preamp needed to drive it.

Danny had been using a different DAC with volume control. I told him that if he wanted the same functionality from our products, he needed a DAC and a preamp, or we needed to go to a modular headphone amp like Jotunheim, with an internal DAC card and preamp outs.

Danny tried the DAC-and-preamp route, and thought it was OK, but that it was a lot of boxes.

“What I really want,” he told me, “Is something convenient for recording engineers doing mobile mastering. They won’t want to mess with a lot of boxes. One box for D/A and volume, plus one speaker amp, especially a small one like Vidar, is ideal.”

“Let’s try the Jotunheim,” I suggested.

We had one with a Multibit DAC card in it, so it was easy enough to swap out. One Jotunheim, one Vidar, done.

Danny listened for a while and seemed very pleased. “This sounds really good! And this can run two Vidars as well?” Danny asked.

“If you want, yes, it has balanced outputs.”

“Then that’s the way I’d want to go,” Danny said. “Jotunheim and Vidar.”

And that was it. That should have been it. That would have been it, if it wasn’t for me. If it wasn’t for me thinking that a Jotunheim R, a Vidar, and the Raal/Requisite resistor box was still a heck of a lot of boxes. If it wasn’t for the idea that came crashing down on me like an oxcart of sledgehammers: what if we just made a direct-drive amp instead?

“You know, we could probably do a direct-drive amp for your headphones,” I told Danny.

Danny blinked at me, as if I’d just asked him if he wanted to join Amway or start a Popeyes franchise together. You know, like I was a bit nuts. Or had Tourettes. Or was just prone to blurting stupid ideas at people I'd just met.

Eventually he found his voice. “I don’t think it would be that easy,” he said, speaking very slowly, as if to someone very stupid.

“I’ve done a lot of high-current amps.”

“It’s a 0.2 ohm load,” Danny continued.

“I know.”

“It would have to deliver seven amps of current,” Danny tried again.

But there was no dissuading me. In the grips of engineering frenzy...catching a glimpse of a new, weird, totally bizarre, completely different, and awesomely fun project, I had no doubt in my mind that this was totally doable. Some mental math gave me the rough idea…it was basically a question of super low rails and super high current, which meant huge efficiency…but nothing insurmountable!

“In fact, I think I can probably hack up a Jotunheim for proof of concept,” I told him. “It shouldn’t have to be any larger physically. We could just try it out with a lab supply and see how it goes.”

Danny laughed and gave me a doubtful smile that said, do whatever you want…but I think you’re a little nuts.

Eddie had been there, watching this whole exchange in silence.

Finally he piped up. “You’ll see,” he told Danny. “This guy’s a genius.”


A Different Opinion

“Genius?” Tyler said, when I told him what happened. “More like idiot. Someone wants to buy stuff you have, stuff you make…stuff we have in stock, and you say, ‘Nah bro, here let me do this pie-in-the-sky thing instead.’”

“Yeah, what he said,” David added. David is our JPL-by-day, hangs-out-at-Schiit-too-much guy who will someday figure out the JPL job is still a time-marking, day-wasting thing to get out of, but yeah, I get it, hanging your ass over the abyss and doing your own company isn’t for everyone.

I laughed. When they said it like that, yeah, it sounded stupid, but this was a really neat engineering challenge, it was something completely different, it was New Idea Day, and they weren’t gonna bring me down.

Heck, I could probably get a proof of concept high-current amp running that afternoon, if I really wanted to.

I had an old Jotunheim board that I could sacrifice. I had a lab supply to run the outputs off of. I could kludge in the 4-pin male connector somehow and get it hooked up, if it looked like it wasn’t gonna blow up or thermally run away.

So what’s holding you back? I asked myself.

Tons of things. There was still an overload of engineering work for real, actual products, products that were already slated for production. This was a silly lark, a distraction, a vanity project for driving exactly one headphone.

But it was a great headphone.

And sometimes you have to follow your whims.

I found the Jotunheim and got to hacking.

Big aside: the engineering behind what I was doing was pretty straightforward. Basically, what I had to do was dramatically increase the Jotunheim’s current transfer efficiency. Jotunheim, as it is, has:

1. Fairly large emitter resistors
2. Dropping resistors in the power supply
3. A transformer with a decent amount of DC resistance in its output (because it was designed for higher voltage rails
4. Output devices designed more for linearity at low output current, rather than brute force.

And there’s nothing wrong with all of this. When used with its target design loads—namely, headphones in the 16-600 ohm region—it works perfectly fine, resulting in a solid, reliable, powerful headphone amp.

But when loaded with a 0.2 ohm headphone, well, it goes to its knees. It’s like running a 16 ohm headphone on Valhalla 2. It just can’t do very much.

So, to maximize current output, I needed to kill as much internal resistance as possible. At the same time, the output voltage rails would have to get a lot smaller, to ensure the amp didn’t go into thermal runaway when the emitter resistors got smaller.

Which really opens a can of worms. Would I need a Vbe multiplier, rather than diode bias? Would it still go into thermal runaway if it got too hot? Would the output devices be a limiting factor?

But that’s engineering. You can obsess about what-ifs, or you can build something and see if it catches on fire. With Jotunheim R, I chose the latter approach.​

So that’s what I did. I got hacking. 4.7 ohm emitter resistors got 50 times smaller. Dropping resistors in the power supply got dropped. I didn’t have a transformer designed for lower rails, so I started with a lab power supply, which would deliver up to 5 amps at any voltage I wanted to set it at, under 30V or so.

In under an hour, I had a Jotunheim R “first hack” version running on a lab supply with +/-4V rails on the output stage. It seemed thermally stable, and it passed signal.

“This is too easy,” I said.

“Except the Raals don’t plug into the female 4-pin output,” David reminded me.

“Crap.” I’d hoped to get it running that afternoon. I would have to order some male 4-pin XLRs and wait for them.

“I can make an adapter,” David said.

He took apart a couple of male XLRs and shorted the internal pins together, making a quick-and-dirty way to connect to the prototype amp.

“Give it a try,” he said.

Gingerly, I plugged in the Raals. Gingerly, because an amp that’s stable without a load might not be stable with a load.

Nothing caught on fire. There was no noise.

That was a good sign!

I turned up the volume a bit. And we had music! Holy schiit!

I mean, boom, there it was, working.

Or so I thought.

I did notice the readouts on the power supply, though. When we started cranking up the music, the output power supply quickly reached readings of 1.5-2A. That’s 1500-2000mA. And. That. Is. A. Ton. Of Current. And it still wasn’t that loud. Danny’s comment about needing 7A to run them suddenly was a lot more credible.

Aside: for example, if I wanted to do Jotunheim R with op-amps, it would take something like 100+ OPA1688 output stages to equal it…and maybe not even then, since the OPA1688 is not so hot at low voltage. That’s a TON of current.​

But it played music!

I put the headphones on and had a quick listen. They sounded…a bit different than I was used to. Bright, and with less bass. But heck, the amp might be oscillating. It might have other problems. The main thing was that it was working—and on the same afternoon!

I took a quick video of it playing and sent it to Danny, with a short note saying, “Hey, this actually works, pretty cool huh?”

A still from the original video:



Danny didn’t reply immediately. Which was probably for the best. Because “working,” is one thing. “Right” is a whole ‘nother thing entirely.


Details, Details

I won’t bore you with the ten thousand design details of Jotunheim R, because, unless you’re an engineer, you probably think I’m a bit nuts anyway.

But there was plenty of hilarity in the design process, starting with Danny’s response to the original video.

Where he asked something like, “That’s cool, did you get the right pinout, and how did you do the baffle compensation?”

Pinout?

Baffle compensation?​

LOL. It turns out that one reason the prototype sounded like ass was that it was out of phase. Running pin-to-pin like David did with the adapters wasn’t correct—Raal uses a different pinout than other 4-pin headphones. So it was out of phase.

Bright? No bass? Check and check.

Aside: but it worked! Clutching real hard to my engineering win!​

Oh, and bright? Yeah, the Raal resistor box isn’t just full of resistors, it also has a couple of big chokes in it for frequency shaping. Since the Raal/Requisite headphones are open baffle, they use the resistor box to compensate for the bass fall-off.

Say it with me: durrrrrrrrrrrrrrrrrr….

Aside: again, it worked! Kinda.​

So those were my first two engineering challenges.

1. Fix the pinout. This was pretty easy, since the male 4-pin connectors could be bent to give the right connections on the board. It’s not something you would do in production, but for a prototype, it was perfectly fine.
2. Get the baffle compensation in there. This was more interesting, because there were a ton of ways to do it, including just using output inductors like Raal, or using a passive network on the input, or doing active compensation in the feedback.

I decided to use active step baffle compensation to start, and that’s what Jotunheim R ended up with, since it worked so well. After measuring the output of the resistor box, I came up with a network that mimicked its effects.

Aside: well, I mimicked its effects as closely as I could do it with an active versus a passive network. ​

And, since the custom transformer I’d ordered came in, I also spent some time listening to it.

Holy moly. My notes at the time were simple: “Scary scary transparent, but distortion in bass is evident.”

The bass distortion turned out to be oscillation. I cured it with different compensation, but I wasn’t happy—the compensation I was using would effect performance. Still, it was worth measuring current output. And it clipped at 7.1A per channel! That was a ton of current…and right where Danny said it should be!

That’s where it got its first development name: Weldenheim, because “it had enough current you could weld with it.” A bit of hyperbole, yes, but still a very stout amp.



But I was disappointed. I wanted to get well above where Danny wanted the current output. Double it, if possible. And Weldenheim should be able to do it. What was the bottleneck?

A few things, really.

One problem was the bridge rectifier. At low voltages, you can lose a ton through the bridge. I changed it to a Schottky.

Another problem was the filter caps were being drawn down. They were a lot higher voltage than they needed to be, so I upsized them by 3X for something that was more congruent with the rails.

But the big thing was the output devices. They really were meant for like 1-2A output each. So the beta was collapsing at high current. I changed them out for new parts—rated at a massive 15A—and the difference was immediately clear.

With the bridge, caps, and output devices, we were now clipping at 10A!

That was more like it.

But could I do better?

I played with a lot of dumb ideas, including trying to keep the rails solid with ultracapacitors. It sounds like a solid idea, but in reality it’s not very bright. Ultracapacitors have a ton of equivalent resistance. Adding them didn’t change the measurements one bit. Factor in the uncertainty of running ultracapacitors on a supply with significant ripple current, and it was best not to go there.

Around this time, we allowed a few people to listen to the prototype, which was still an old Jotunheim board, with a bunch of parts flying in the air. We had to warn them not to turn it up for long (I knew I would need a heatsink, but I didn’t have one at the time).

And their response?

“Wow, this is cool that it works…but hmm, it is helladangheckadoodle edgy, ain’t it?”

Well, those weren’t their exact words, but I could see it. They were impressed it worked at all, but they weren’t happy with the sound. Dissappointing.

Of course, we could just go back to selling Vidars and Jotunheims, and be done with it.

But. No.

I knew what I really needed to do: I needed to move Jotunheim R over to Nexus™.


Into the Nexus

Why Nexus? Mainly because it sounds better.

And yeah, I know I’m gonna get crucified for this, especially after my comments about how small the differences were on the Magni 3+/Heresy blind listening.

Go ahead. Crucify me. That’s fine. Sometimes things may have a bigger effect. Nexus is a much more tonally rich, “wet”-sounding topology than Pivot Point. It’s also easier to compensate. I suspected it would be much better in the real world.

So I started the hard work: putting Nexus on a Jotunheim-sized board, while also doing the changes necessary for the Raals—adding the baffle step compensation, changing the output connector, etc. The end result was a 4-layer board like Jotunheim, but one that was significantly more complex, with the need for many matched parts. I also added something that I thought many pros would find useful: a way to disable the preamp outputs. It also got a host of other little tech changes like a revised high-voltage supply and proper Vbe multipliers for biasing.

Aside: unlike Jotunheim, Jotunheim R’s preamp outputs are passive. I got a little paranoid about someone maybe shorting a preamp output to ground, so I went this way instead of an active preamp output. Equal numbers will hate me or love me for this decision; it’s the way things work.​

On first start-up, with a slightly tweaked transformer, the Weldenheim, Nexus Edition started up and worked…and it didn’t oscillate like the original. Which meant that compensation was easier.

But, when cranked up, it still oscillated when it hit the rails.

Argh.

Then I remembered: wait a sec, this is a super high bandwidth amplifier, running tons of current into a low impedance load. It might need a Zobel network on the output!

Aside: a Zobel network is common to most speaker power amplifiers, and helps ensure that the speaker amp sees a defined load impedance at high frequencies. It’s not typically used in headphone amps…but Weldenheim had grown far beyond most headphone amps!​

I pasted on a Zobel network (just the parallel C+R part, scaled for the Jotunheim R’s expected impedance load)…and BOOM, there you go. Fully working, no oscillation.

And, most importantly, it delivered over 13A, both channels driven, into the Raals. This was when I started worrying about smoking the headphones, they were getting so loud.

Okay. It wasn’t double what Danny said, but it was enough.

It was time that I had Danny and some other listeners back to hear it. And this time, they were all smiles. No comments about the brightness or edge. In fact, Danny thought it was a little rolled. So we tweaked the baffle step compensation a bit until he was happy.



So was I done?

No. Not even.

It wasn’t even a product yet.


Connecting to the Real World

So why wasn’t Weldenheim (er, Jotunheim R) a product yet? If it performed well, and sounded good, you’re done, right?

Ah. No.

The problem with reality is, there is this place called The Real World, where unexpected things can happen.

Unexpected things like someone running Jotunheim R all the way up until it got so hot it cooked itself (we’re talking gross distortion, pure crazytown stuff, things nobody would want to listen to—except someone DOES), or making an adapter to run Jotunheim R with TRS headphones (which would short the outputs, and, in the case of the prototype, would let all the magic smoke out.)

To make it a real product, we would have to add:

1. Over-temperature protection.
2. Over-current protection.

But there were a ton of gotchas here as well. Over-temperature, in our speaker power amps, is monitored by a microprocessor connected to a linear temperature sensor. Over-current, in the speaker power amps, is also overseen by the microprocessor, in conjunction with a complex ground-current-sensing scheme that wouldn’t work with Weldenheim’s transformer.

Aside: the plain-Jane Jotunheim doesn’t need this level of protection—it’s designed to gracefully fade as current output increases, thanks to its internal levels of resistance. When you start going for maximum current transfer, though, you lose this internal protection.​

I really didn’t want to throw a microprocessor in Jotunheim R, because it was already complex and expensive, thanks to the exotic parts and short run sizes. Developing firmware for a short-run product wasn’t all that appealing, either.

It took a while to figure a way around it, but I eventually ended up with Hall-Effect current sensors (which are technically not in the signal path at all, they simply sense the current passing through an internal wire) and a thermostat (rather than linear current sensor). With some simple old-school analog logic, I was able to create a protection system that will mute the output if Jotunheim R tries to source over 31A from both channels, or if it goes over 95 degrees C on the heatsink (plenty safe for devices rated for 175 degrees C continuous.)

Aside: yes, 31A. That’s thirty-one AMPS. And yes, you can trigger this protection on the APx when testing into the Raal headphones and running a signal of more than 2VRMS into the amp. ​

The next prototype included the Hall Effect sensors, the thermostat, screws for a heatsink (custom from AAVID, designed to fit under the True Multibit DAC card), and, most importantly, switching for the baffle step compensation. Because, who knows, maybe Raal/Requisite will come out with ribbon headphones that don’t need baffle compensation, and then it would suck massive donkey balls if you had to buy a whole new amp for that. Or maybe other companies will come out with ribbon headphones. Or maybe you want to run a dozen pair of Magneplanar LRS in parallel off this amp (only partially kidding, more on that later.)

And that was that. I figured we were ready for production. I had our PCB assembly house do a half-dozen prototypes of this version, figuring we’d send them out to various listeners and see how they did.

When the boards came in, they worked…with a couple of hilarious exceptions:

1. The baffle compensation and preamp enable switches worked in reverse. Yes, I am an idiot. Maybe you already knew this.
2. The protection system worked, but thanks to me leaving a couple of key capacitors off, it made a weird whining noise as it came up to operation (this was a physical whine from the chassis itself, not through the transducers.)

Still, it was good enough to put a “Production Qualifier” badge on, and see what people thought. The next rev could clean up the switches and protection oddities.



This is where we could start getting serious. We sent all but one of the production qualifiers out to listeners and reviewers who were familiar with the SR1a headphones, and asked them if they noticed any glitches or operational oddities, as well as what they thought of the sound.

Everyone was thrilled. Some said it even sounded better than many speaker amps. The amps worked fine, and the protection system worked as expected.

Time to start up production!

I made a couple of board revs, sent the board out, and commenced to speculate about possibly having the Jotunheim R out at the end of 2019.

Aside: I’ve said I’m an idiot, right?

Aside to the aside: but we didn’t miss by that much, right?​

And that’s what we’re launching today: a production Jotunheim R. As of this writing, it is the first and only direct-drive ribbon headphone amp in the world. It substantially simplifies using the Raal/Requisite SR1a headphones, eliminating the need for the resistor box, speaker amp, DAC and volume control. It’s a one-box solution for one of the best headphones in the world, and it’s ready for any future ribbon headphones that don’t need baffle compensation.

“Well, that’s all great, Stoddard,” someone will say sarcastically. “But if you hadn’t been doing your pet project for one single headphone, what else could you have been doing?”

Great question.

Because sometimes you have to look around corners.

Ask the Apollo program guys.


Technological Fallup

Fallup. Not fallout. Because this is a good thing.

As with the Apollo program, which arguably significantly accelerated, or directly birthed, many of the technologies that have us glued to phone screens for 18 hours a day, the Jotunheim R project has had a big impact on us.

How?

Let’s start with this interesting observation: Jotunheim R is more than just a ribbon headphone amp. In fact, it’s a damn nice speaker amp. It laughs off 8 ohm loads like Ragnarok 2 laughs off 32 ohm headphones. Hell, it’s under 0.001% THD at 1W into 8 ohms.

The catch? It also maxes out at like 3.2W into 8 ohms. That’s the low rail voltages working against you. I didn’t test it, but it would probably do almost 6W into 4 ohms and 10W into 2 ohms. Maybe. Don’t quote me. However, here’s the thing: you could wire up an adapter, and run speakers all day off the Jotunheim R.

But there’s more. Remember, it can also drive insanely low impedances.

So, what about hooking up, say, 10 pairs of Magneplanar LRSes in parallel? It should drive that just fine. How would it sound? I don’t know. Just blue-skying here. But Jotunheim R opens up new things we can play with. Which is pretty cool.

“Sounds pretty niche, Stoddard,” someone says. “I don’t want a fleapower amp that I have to make adapters for, and I don’t want to buy a metric asston of Maggies.”

Cool. Because there’s a lot more fallup. It’ll just take a while longer to appear.

In fact, one of the key technologies I mentioned in last year’s wrap-up chapter, OG tech, is a direct result of Jotunheim R development. OG is already working in a proof-of-concept prototype, and, with more refinement, could end up being a foundational technology that leads to whole new classes of products. I really can’t say more, because there may still be something I missed, but this looks like a very, very good thing.

But that’s only one new piece of technology. While developing Jotunheim R, I was excited by the possibilities so much, that I came up with other new ideas. I still have yet to prove some of them, but they are also things we’ll be working on this year.

So yeah, Jotunheim R may have seemed like a distraction…but in reality, it was something that led to entirely new vistas. Sometimes you have to get weird, chase the bizarre, and have some fun. Because you don’t know where it might go.

Hi Jason. I've listened to one of the Jotunheim R preproduction units, and I have one question: can you make a more powerful version? Maybe something equivalent to two vidars in monoblock mode?
I'm asking because just as I got to an enjoyable volume level, the unit I was listening to started clipping.. So a Jotunheim R with more power will offer more peace of mind, at least for me that is.
This was what I was listening to when the clipping hapened by the way. Lots of electronica and bass.

 

[Jason Stoddard]

Hi Jason. I've listened to one of the Jotunheim R preproduction units, and I have one question: can you make a more powerful version? Maybe something equivalent to two vidars in monoblock mode?
I'm asking because just as I got to an enjoyable volume level, the unit I was listening to started clipping.. So a Jotunheim R with more power will offer more peace of mind, at least for me that is.
This was what I was listening to when the clipping hapened by the way. Lots of electronica and bass.

Odd, because I've never had any problem getting to ear-bleeding levels on Jotunheim R with the SR1a, definitely above a Vidar into the resistor box.

With respect to a more powerful box, anything's possible--for several times the price, and in a much larger physical size. There are currently no plans for this.

 

[Tim van der Leeuw]

Use an aquarium as music storage? Nice plan.

And finally I found the ultimate Snake Oil company website.
See for yourself all those beautiful products you can't do without.
Wear aluminum thongs to protect the nuts to be sure.
https://telos-audio.com.tw/

Not sure they fully understand their target-audience if they've got this product showing on a background-picture on their website...

 

[tincanear]

Gungnir MB-->SYS-->Aegir is my recommendation.

@Brubaca if you had stated that the sys was being used with volume maxxed out (just as a switch box, instead of being used to control the volume), then that changes my recommendation to that @sam6550a just listed. Interconnects should be of the low capacitance type, and kept short (1m max) especially between the Sys output and Aegir input.

 

[W S L]

Odd, because I've never had any problem getting to ear-bleeding levels on Jotunheim R with the SR1a, definitely above a Vidar into the resistor box.

With respect to a more powerful box, anything's possible--for several times the price, and in a much larger physical size. There are currently no plans for this.

Ok, i just talked to my dealer, and apparently i got the baffle compensation switch in the wrong position, because i followed what was written in the online instructions manual. Will try again later.

 

[Roy G. Biv]

Not sure they fully understand their target-audience if they've got this product showing on a background-picture on their website...

Anybody that knows anything about "Quantum Resonation Conditioning" knows that it can lift even the lowliest of earbuds to stratospheric levels. Sheesh....

 

[earnmyturns]

@earnmyturns, were you at Berkeley, by any chance?

No. Got to work with Unix as a graduate student and research assistant in Edinburgh.

 

[Scott Kramer]

Got exposed to HP-UX as a baby-- can zip around/script/c/vi in linux, rasppi, macos cmdline like it's nothing. Funny how windows cmdline's actually the weird one!

 

[Pietro Cozzi Tinin]

Anybody that knows anything about "Quantum Resonation Conditioning" knows that it can lift even the lowliest of earbuds to stratospheric levels. Sheesh....

Oh not only cheap earbuds. Just ask Constanza.

 

[Brubacca]

@Brubaca if you had stated that the sys was being used with volume maxxed out (just as a switch box, instead of being used to control the volume), then that changes my recommendation to that @sam6550a just listed.

I'm sorry, I can be a bit thick.

If I go Gumby, SYS , Aegir then I would be using the volume pot in the sys. Still recommend this?

The Naim UnitiQute is an integrated amp with IC Chip volume control. Right now I only use Sys as switch box.

 

[Roy G. Biv]

Oh not only cheap earbuds. Just ask Constanza.

From your avatar, it appears that Feline Quantum Resonation Conditioning might often be met with some resistance.

 

[sam6550a]

I'm sorry, I can be a bit thick.

If I go Gumby, SYS , Aegir then I would be using the volume pot in the sys. Still recommend this?

The Naim UnitiQute is an integrated amp with IC Chip volume control. Right now I only use Sys as switch box.

The SYS is totally passive. If the SYS volume control is at about 10 o'cloock or greater, you should not experience any sound quality loss, since Gumby has a low [75 ohm] output impedance.

 

[tincanear]

I'm sorry, I can be a bit thick.

If I go Gumby, SYS , Aegir then I would be using the volume pot in the sys. Still recommend this?

The Naim UnitiQute is an integrated amp with IC Chip volume control. Right now I only use Sys as switch box.

Yes, try going Gungnir MB > Sys > Aegir using short ~0.5M interconnects. If bass and dynamics suffer, then add an active preamp (Freya S or Freya +). Either Freya will allow for adding a second Aegir (dual Aegirs in monoblock mode) for more power if needed.

 

[tincanear]

The SYS is totally passive. If the SYS volume control is at about 10 o'cloock or greater, you should not experience any sound quality loss, since Gumby has a low [75 ohm] output impedance.

Actually, I believe with the 75 ohm output impedance of the Gungnir MB, the effective source impedance seen by the amp input is minimized at the extreme ends of the volume control range (and is highest in the middle third of its range, reaching a max of about 5K). The 22K input impedance of the Aegir will result in a loss of a dB or two across the band (not an issue in this situation). The high frequency roll-off will depend on the interconnect capacitance as well as the Aegir's (unspecified) input capacitance. The Aegir is all BJT, so it doesn't have JFET inputs (which can exhibit varying input capacitance with respect to input voltage, which leads to non-linear distortion when used with passive or other high output impedance (some all tube) preamps). Unless someone has this setup and has an Audio Precision or Avermetrics handy, gonna have to try it and see how it sounds...