Power Output:

Stereo, 8 Ohms: 10W RMS per channel
Stereo, 4 Ohms: 15W RMS per channel
Mono, 8 ohms: 30W RMS 

Frequency Response: 20Hz-20Khz, +/-0.01db, 3Hz-500KHz, +/-3dB

THD: <0.004%, 20Hz-20KHz, at 1V RMS into 8 ohms 

IMD: <0.005%, CCIR, at 1V RMS into 8 ohms

SNR: >117dB, unweighted, referenced to full output 

Damping Factor: >100 into 8 ohms, 20-20kHz

Gain: 10 (20dB)

Input Sensitivity: AKA Rated Output (Vrms)/Rated Gain. Or, 9/20. You do the math.

Input Impedance: 20k ohms SE, 40k ohms balanced

Crosstalk: >80dB, 20-20kHz

Inputs: L/R RCA jacks for stereo input, single XLR for mono input

Topology: Continuity S output stage; fully discrete, fully complementary current feedback, no capacitors in the signal path

Oversight: over-current and over-temperature sensors with relay shut-down for faults

Power Supply: 80VA transformer, 30,000uF filter capacitance, plus boosted, CFP-regulated supply to input, voltage gain and driver stages

Power Consumption: 80W maximum 

Size: 9” x 6” x 2.5”

Weight: 8 lbs

Audio Precision APx555 Report for Gjallarhorn

10W? That doesn’t seem like a lot.
In an era where there are options that claim, like, a billion watts, from a box small enough to lose in the couch cushions, yeah, we hear you. This isn’t the amp to do party tricks like seeing if you can get to 115dB output in your stadium-sized living room.

So what’s this amp for?
For everyone who wants a super-high-quality amp for desktop, nearfield, and small room systems.

But will it go loud?
Put Gjallarhorn on your desk, connect it to any normal pair of speakers, and you’ll definitely get to leasebreaking levels, like, pronto. If you share walls, expect to hear the neighbors yelling to “turn it down!”

What do you mean by “normal speakers?”
Pretty much anything from a 2-way 4” bookshelf to refrigerator-sized horn speakers. As in, not planar speakers. Not what Eddie used to call “barking screens.” And not 2 ohm, 79dB efficient DIY jobbies. You know, normal speaker speakers that people buy on Amazon or at more hoity-toity kinda stores.

So this is just a desktop amp?
Nope! It’s perfectly capable for smaller rooms, too, especially if you have some of those refrigerator-sized horn speakers we mentioned previously. Or even smaller horn speakers. Fun fact: 10W out of Gjallarhorn with 95dB efficient speakers is like 100W out of Vidar into 85dB efficient speakers.

Are you saying this could be the only amp I need?
Maybe. For desktop duty, almost certainly. For smaller rooms, depends on your speakers. You’ll want to go with more efficient speakers if you want to get decent volume in a room setup. For more power, you could also double up Gjallarhorns and run them mono, or, if you’re really in doubt, Vidar is gonna be great for pretty much anything you throw at it.

Can I stack this with your desktop headphone amps?
Some of them, yes. It might get a little too hot sitting on top of an old Asgard 1, but Asgard 2 and Jotunheim are usually fine (and the exact same size as Gjallarhorn.) In this case, you’d stack Gjallarhorn on top. It may not work so well in warm rooms (over 25 degrees C).

Can I stack with your preamps?
Saga is exactly the same size, but it has a tube sticking out of it. You can always run them side by side in many equipment racks.

So is this kinda like a mini Vidar 2?
Kinda. Ish. It has a more sophisticated output stage—Continuity S—than Vidar 2. But it uses different output devices. Beyond that, in broad strokes, they are similar. Similar gain stage, similar linear power supply, etc. The protection system on Gjallarhorn is all analog, though—no microprocessor—but still incorporates overcurrent, over-temperature, and DC protection.

No class D?
No.

No switching supplies?
No.

Some of my friends are super into Class D and say it’s the future.
There are plenty of Class D amps out there. Gjallarhorn isn’t one of them.

Let me have a breakdown of the tech, using words of less than 6 syllables.
Okay, here goes:

1. Fully discrete, current feedback topology is amazingly fast (-3dB above 1MHz before input filter) and measures well, especially for such a simple stage.
2. 2 pairs of 10A output transistors per channel, including one pair used for Continuity S stage to provide greater transconductance linearity.
3. 100% DC coupled throughout, no capacitors in the signal path.
4. Fully linear, all-internal power supply with 80VA toroidal transformer and 30,000uF filter capacitance in the main rails, plus 13,200uF for the boost rails.
5. Separate discrete regulated boost rails improve efficiency and are ground-referenced (not stacked) to ensure each channel’s performance is independent from the other.
6. Analog protection system uses a “least invasive methodology”—no active devices in signal path, no current limiting, no crowbars—just current and thermal sensor and DC servo.  
7. 4-layer PC board for optimal layout and current flow.
8. No fan.

You mentioned I could use these in monoblock mode. How does that work?
It’s not a mode. It’s just the natural result of driving each channel with one half of a truly balanced signal. To use Gjallarhorn as a mono amp, you need a preamp with truly balanced outputs. A Jotunheim or Freya will do fine, as will any other source with a real balanced output. 

You don’t rate power for 4 ohms in mono. Why?
Gjallarhorn will run 4 ohm speakers in mono just fine—up to a point. At which point, the over-current or over-thermal protection will kick in and your fun will end. That point is about 30W output, just like into 8 ohms. So not very exciting. If you need a ton more power, there’s always Vidar.

So what’s a Gjallarhorn?
Gjallarhorn, in Norse Mythology, is Heimdall’s “loud sounding horn.” And believe us, this is one loud sounding horn if you have any decent 5” 2-way speaker and neighbors living on the same wall opposite you!

Gjallarhorn Manual