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Class A Headphone Amp & Preamp

Voltage (?)
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Ships 1-3 days





Tired of compromise? Kinda crazy when it comes to sound? Then maybe you’re in the mood for Mjolnir 3, a real-deal, 100% Class-A, no-feedback, dual-mono, choke-input, fully-discrete, balanced-differential headphone amp and preamp. It’s by far the most extreme desktop product we’ve ever done.

Class A. No Kidding.
By real Class A, this is what we mean: pure single-ended Class A, as in, the Class A that defined Class A, the Class A that can’t go out of Class A, the Class A everyone wants you to think about when they’re talking Class A. We wrote a chapter on it here. And, just to prove we aren’t totally crazy, we also gave you the option to switch to push-pull Class A, for more power.
No Feedback. Or Not.
As in, Mjolnir 3 is also a no-feedback amplifier. Or, if you’re in the mood, you can switch in feedback. Because audio is about choice. 
Dual Mono. Choke Input.
Dual mono means that the left and right channels on the Mjolnir 3 share nothing, except the same circuit board. Each channel has its own power supply, including discrete regulation, separate choke, and separate transformer. And the choke input itself is a super old-skool way of power supply smoothing and energy storage, unlike anything else out there.

Fully Discrete. Balanced Differential.
Mjolnir 3 employs a super-simple, complementary-pair, discrete balanced differential topology we call Equipoise™. And we mean discrete, right down to the power supply—no IC regulators here. And by balanced, we mean balanced, for real, from input to 4-gang pot to output—no conversion. 
Completely Overengineered. Totally Convenient.
Mjolnir 3 is so utterly overengineered that it uses two Gjallarhorn heatsinks (as in, heatsinks usually used in a speaker amp capable of delivering 30W into 4 ohms) and 32 10A-rated output devices (yes, thirty-two, 10 amp rated devices) to drive your headphones. At the same time, it provides the convenience features you want, like switchable gain (without feedback), balanced and single-ended inputs and outputs, and switchable preamp outputs.
Designed and Built in California
By “designed and built in California" this is what we mean: the vast majority of the total production cost of Mjolnir 3—chassis, boards, transformers, assembly, etc—goes to US companies manufacturing in the US. Our chassis are made minutes from our facility. Our PCBs are done just over the hill from us. Our transformers are made in NorCal. You get the picture. 
5-Year Warranty and Easy Return Policy
Mjolnir 3 is covered by a 5-year limited warranty that covers parts and labor. And if you don’t like your Mjolnir 3, you can send it back for a refund, minus 5% restocking fee, within 15 days of receiving it.

Frequency Response: 20Hz-20Khz, +/-0.01db, 2Hz-700KHz, -3dB

Balanced Headphone Output:
Maximum Power, 32 ohms: 2W RMS per channel 
Maximum Power, 300 ohms: 1W RMS per channel
THD: <0.015%, 20Hz-20KHz, at 4V RMS, 300 ohms
IMD: <0.02%, CCIF, at 4V RMS, 300 ohms
THD: <0.05% 20-20kHz at 1V RMS, 32 ohms
IMD: <0.06%, CCIF, at 1V RMS, 32 ohms
SNR: >110db, A weighted, referenced to 4V RMS
Crosstalk: >-90dB, 20Hz-20kHz
Output Impedance: Less than 0.25 ohms
Single-Ended Headphone Output:
Maximum Power, 32 ohms: 1W RMS per channel
Maximum Power, 300 ohms: 500mW RMS per channel
THD: <0.025%, 20Hz-20KHz, at 2V RMS, 300 ohms
IMD: <0.03%, CCIF, at 4V RMS, 300 ohms
THD: <0.1% 20-20kHz at 1V RMS, 32 ohms
IMD: <0.15%, CCIF, at 2V RMS, 32 ohms
SNR: >98db, A weighted, referenced to 2V RMS
Crosstalk: >-85dB, 20 Hz-20KHz, 300 ohms
Output Impedance: Less than 0.13 ohms
Input Impedance: 50K ohms
Gain (balanced input): 2 (6dB) or 8 (18dB)
Gain (SE input): 1 (0dB) or 4 (12dB)
Inputs: Balanced XLR and Single-Ended RCA, relay switched
Outputs: Balanced headphone (4-pin XLR), single-ended headphone (1/4” TRS), switchable balanced and single-ended line preamp
Gain Stage: Equipoise™ fully discrete, high voltage, differential zero feedback single-ended or push-pull class A, DC in and out; selectable feedback and gain independent from feedback; 16 10A bipolar NPN output devices per channel
Power Supply: Full dual mono, choke input, 2 48VA transformers and 2 chokes, separate 100V front end rail for each channel, 100% discrete regulation with over 20,000uF filter capacitance per channel. 
Power Consumption: 50W typical
Size: 16” x 8” x 2”
Weight: 16 lbs

You know this thing runs really warm?
We know it runs really hot. You may call it only “warm.”

And you aren’t worried about the longevity? 
No. Because we know how to engineer things that run hot for a very long time. Like the original Asgard, many of which are still in service, 13 years later.
So you’re using all these technical terms like Class A and dual mono and choke input and no feedback and fully discrete and I don’t really want to understand all that, can you sum up?
Sure. Mjolnir 3 is a big, hot, crazy throwback of an amp that’s our all-out shot at the most extreme headphone product we could make, and still fit on a desktop.
But it doesn’t have any screens and blutoof and all that!
Correct. It doesn’t even have a DAC, in fact. 
Seems kinda…old skool.
Right. I think we used those exact words. And we’re fine with it being a big, simple amp. We intended it to be that way. Unlike some of our more advanced products, Mjolnir 3 was intended to be simple and mechanical. It doesn’t have a microprocessor or even motorized pots. It’s a big, blunt instrument…a hammer, so to speak.
Does it sound like a hammer?
We personally think it sounds better than a hammer.
But what does it sound like?
Everything and nothing at once, and all in-between, with unicorns and rainbows and free shrooms; come on, you guys know by now we don’t describe our products with insanely flowery prose, right?
So does it measure good?
For a no-feedback topology, it measures OK. By the standards of the Measurement Uber Alles crowd, no, it doesn’t. We have other amps for that. They cost $109 and $199 and $399, take up much less room on your desk, have higher output power, are quieter, and don’t get as hot. So there you go.
Can I drive difficult headphones with this?
Absolutely. 2W RMS Class A is a lot more than you think. Especially with chokes backing it up.
Can I run IEMs with this?
We wouldn't recommend it. Seriously, you want to run IEMs on a 16-lb desktop amp?
Wait a sec, what is this single-ended Class A? I thought this was a balanced Class A amp?
It is. It allows you to choose two different operational modes. One is single-ended Class A. As in, the output stage is biased by a fixed current source. It’s considered to be the most “pure” form of Class A. However, for higher power, you can switch to push-pull Class A, where the current source is modulated, as in a White cathode follower. But this amp is balanced and differential all the way through, which is separate from Class A.
And I can choose feedback or no feedback?
Yes. You can switch in overall feedback, or leave it off.
Why would I want feedback?
Hey, you tell us. Seriously, though, there may be systems or components where it’s beneficial. Try it. It won’t kill you. You may decide you like what it does. Or you may not like it at all. Both are fine. We’re not here to judge. You can order the Boone’s Farm and we won’t laugh. Well, maybe we will.
There’s also a gain switch. How do you change gain without changing the feedback?
We change the gain by changing the degeneration of the input stage. This isn’t part of the overall feedback.
Wow, that’s a lot of options.
Yep! We wanted to give you a lot of ways to tailor the output of Mjolnir 3 to your system.
How does this amp relate to the previous Mjolnirs?
It’s totally different. The previous Mjolnirs were circlotron-style topology designs, and one had tubes. Neither was dual mono, neither had choke input, neither had giant heatsinks, neither was really Class A. This is a totally different design. It retains some ideas from Mjolnir 1, in that it uses a high-voltage (100V) front end stage to increase linearity without feedback, and is super-simple in overall topology. It borrows some ideas from the Freya+ differential buffer stage as well, which is the first place we used a Equipoise-style topology.
I still don’t understand this choke-input thing?
Choke input power supplies were the old way of smoothing AC power on its way to DC. It was left by the wayside due to economics—a choke is a big, heavy, expensive hunk of iron and copper, whereas capacitors are relatively small and light. We went back to chokes because our experience with Tyr. At the same time, there are plenty of caps in there too. And 100V rails with discrete regulation. And each channel has its own transformer, choke, capacitors, and regulator. Bottom line: the power supply is totally nuts, over the top.
So is it a linear power supply?
100% yes.
Can I get a bigger linear supply?
Yes, if you have an engineering degree or working technical knowledge of power supplies and design a completely different, much large product. Come on, this doesn’t have a wall-wart!

What if I want tubes?
See above. Have fun designing your own stuff. Seriously, more people should DIY. But we understand if you don’t.
You know I have this amp that says it’s Class A but it runs cool?
You know that’s BS, right? Try this chapter here.
What is Mjolnir?
In Norse mythology, Mjolnir is Thor’s hammer. Seems appropriate, doesn’t it?