I have the Bifrost before this and plugged this into my Valhalla before my Mjolnir arrived.  Even though it uses the same D/A chip as the Bifrost, I found it to be a significant upgrade that I could even hear with the Valhalla and my Beyerdynamic DT990 (600 ohm).  If I could only choose between the Gungnir or Mjolnir for upgrading my headphone system, and my headphones didn't require the extra power, I would probably go with the Gungnir, it was a more noticeable upgrade.  The Mjolnir was noticeable but unless your gear really requires that power, it probably will be less noticeable for you.  Even with the single-ended connections I was using with the Valhalla, it was noticeable.  I am using it at work.  I connect my macbook to a M2Tech Hiface to the Gungnir coax port.  If you get the USB version you shouldn't require the Hiface.  I am using a Pure i20 for my old iPod to stream lossless to the optical port.  This lets me use either the computer or the iPod with my Gungnir, and they both sound great.  I have since upgraded from the Valhalla to the Mjolnir.  My headphones have been upgraded to the Hifiman HE-4.  I have recalbled all of my headphones to balanced and am not looking back.
 
Not sure if I feel hard-pressed to upgrade at this point either.  The statement DAC supposedly includes a lot more power, but I think I could even upgrade to the HE-6 and still use what I have just fine.  Bottom line, the Gungnir has really made me feel like I have taken it as far as I needed to take it.  My headphone system sounds better than my home system now.  So obviously the money needs to go towards upgrading the home system now lol...

I'll start off by saying I prefer solid state to tube. I always found tube to be rather limiting and muddy, and I'm sure its just because I haven't listened to or owned really good tube gear.

I started off my Schitt journey with the Asgard, then got the Bifrost, and then decided to try the Valhalla. I found the Asgard/Bifrost combination to be a bit dry and clinical for my tastes. I wanted something a bit (as the marketing went) red dress in a smoky room... hehe. So after some hemming and hawing and saving, I splurged for the Valhalla. I figured I could sell my Asgard to make up some of the money....

Well I was impressed. But not how I expected to be. The sound was more dynamic, more full, but I really didn't pick up any of the red dress and smoky room "life/lushness/organic/etc" I was hoping for. I still find the sound to be a bit on the clinical side for my tastes. I can't argue - this Valhalla sounds better than the Asgard, I am hearing more in my music than I did with the Asgard, but it wasn't a huge upgrade. If I was to do it again, I would get the Asgard and be happy with it. But Valhalla is a BIT better, so of course I have to keep the Valhalla after listening to it. haha.

The Valhalla chassis gets every bit as warm as the Asgard, but the Asgard is warm on the bottom and the Valhalla is warm on the top. I have to be a bit more cautious about leaving it on, as it will burn out the tubes quicker of course. So at lunchtime, I turn it off, where with the Asgard I left it on without worry.

Headphone-wise I used it with a variety of cheaper units:
Panasonic RP-HTTF600, Monoprice 8323, Beyerdynamic (DT770 250 ohm, DT880 250 ohm, DT990 600 ohm), Grado SR80i, AKG271 MKII, Bowers & Wilkins P5, Sennheiser HD-280. The Valhalla handled all of them well, even the 600 ohm. I never felt like I was pushing the amplifier very hard with any of these. I also have some JH Audio JH-5 IEMs but I didn't test those because they are not supported on this amp.

I listen primarily to 24/96 vinyl rips that I make on my home system (Clearaudio TT, Grado Reference cart, E-mu 1212m ADC, after a thorough vacuum clean of the vinyl - i am pretty anal about it). I listen to a variety of genres, and find myself enjoying this amp for rock/pop type of music. Like most of the Schiit offerings, it doesn't have qualities that (to me) favor certain types of music - very neutral sounding.

In conclusion, the tubes adding something to the sound, but not quite what I was looking for. I wish I could have some more Red Dress and less Lab Coat, but honestly overall its a very capable unit for the price and regularly brings smiles to my face. The more I turn the volume knob, the better it sounds - and isn't that what its all about?

Before getting this DAC, I ran my Asgard thru a Pacific Valve NOS DAC. I also compared this in my main home system to a Audio-GD Reference 1 DAC.

When I first received it, it went into my home system for the comparison against my Audio-GD. Its not really a fair competition, but I found the Bifrost held up a lot better to rock/metal fast type of music. It was very clinical and detailed compared to my Audio-GD. I didn't find myself wanting for anything, but when I plugged in my Audio-GD I found that the music gained more life, thickness, and personality. So that let me to believe that this was a highly capable, if boring, DAC.

I then brought it into work and replaced my PV NOS DAC and found myself thinking the same thing. Compared to the Pacific Valve, it was a lot more detailed and "cleaner" sounding. I am still using the Bifrost and I don't think its bad at all, but I am glad i have other DACs I can listen to to gain new insights as well. The Bifrost is like the Nerd who gets everything pretty much right and makes few (if any) mistakes, but sometimes you need to experience something a bit more personable

I'm not particularly high end, but I like to try things and compare.

Headphone-wise I used it with a variety of cheaper units:
Panasonic RP-HTTF600, Monoprice 8323, Beyerdynamic (DT770 250 ohm, DT880 250 ohm, DT990 600 ohm), Grado SR80i, AKG271 MKII, Bowers & Wilkins P5, Sennheiser HD-280.

I also plugged in my JH Audio JH-5 IEMs, and it also sounded good, in fact these pulled the most detail out of everything I tried.

I listen primarily to 24/96 vinyl rips that I make on my home system (Clearaudio TT, Grado Reference cart, E-mu 1212m ADC, after a thorough vacuum clean of the vinyl - i am pretty anal about it). I listen to a variety of genres, and find myself enjoying this amp for rock/pop type of music. Like most of the Schiit offerings, it doesn't have qualities that (to me) favor certain types of music - very neutral sounding.

After living with the Asgard amp for awhile, I swapped it out for the Valhalla, and felt the Bifrost held its own with that amp as well. I was hoping the Valhalla would warm up the sound more and breathe some personality into the Bifrost, but I found it really did not. (not that I am disappointed - just something to keep in mind).

Hate to sound like my review is hating on the DAC because I actually like it a lot. I use it over my Pacific Valve DAC exclusively now. Makes the NOS sound a bit muddy when doing direct comparison. Just wish I could have Bifrost clarity with a bit more thickness and lushness. I will have to look into the Gungnir

One annoying thing for those that use it hooked up to a computer. It has a relay that clicks on/off after a little pause. So if you are leaving the DAC turned on while you are doing doing computer stuff with no music playing... you will get an annoying click. i.e.: if you empty the trash on your computer you get CLICK! -empty trash sound- CLICK! as the DAC "turns on" and then "turns off" - and there's no way to get around this except to leave music playing all the time. It took me awhile (longer than I hoped) to get past this, but I now ignore it.

I used it exclusively with the TOSLINK optical port. I may eventually get a M2TECH HiFace for my computer and go coaxial. If I notice any difference I will update this review again.

This was my first dedicated headphone amp. Before this, I ran a couple of component stereo receivers on my desk at work. I enjoy listening to my higher end home stereo system, and listening on my daily walk with my IEMs (in ear monitors)

Initial impression of the chassis is very nice. It looks solid, feels solid, but can get very warm, so position it accordingly.

I used it with my NOS Pacific Valve Fathom DAC, as well as straight from the computer. With a dedicated DAC, it obviously sounded better. After upgrading from my Pacific Valve NOS DAC to the Bifrost, I found it sounded even better. The two devices were better matched. The darker sound of the NOS seemed a bit fuller and brighter with the Bifrost.

Headphone-wise I used it with a variety of cheaper units:
Panasonic RP-HTTF600, Monoprice 8323, Beyerdynamic (DT770 250 ohm, DT880 250 ohm, DT990 600 ohm), Grado SR80i, AKG271 MKII, Bowers & Wilkins P5, Sennheiser HD-280. The Asgard handled all of them well, even the 600 ohm. I never felt like I was pushing the amplifier very hard with any of these.

I also plugged in my JH Audio JH-5 IEMs, and it also sounded good, but there was a very slight hum. I suspect the hum is also present in the other headphones, but the very sensitive IEMs could detect it more. I tried putting on a different circuit than my computer, tried using a non grounded plug adapter, and it just didn't go away.

This hum wasn't annoying enough to dissuade me from this amp, but I wanted to try their tube Valhalla, so I sold this one and upgraded. But to be honest, if I was doing it all again, I would just stick with the Asgard. The upgrade really wasn't significant enough with my headphones to be able to tell much. Surprisingly, the Valhalla was a bit brighter and had more bass, but it was very slight. I think this Asgard is that much of a good deal.

I listen primarily to 24/96 vinyl rips that I make on my home system (Clearaudio TT, Grado Reference cart, E-mu 1212m ADC, after a thorough vacuum clean of the vinyl - i am pretty anal about it). I listen to a variety of genres, and find myself enjoying this amp for rock/pop type of music. Like most of the Schiit offerings, it doesn't have qualities that (to me) favor certain types of music - very neutral sounding.

I'll post reviews of the Bifrost and Valhalla next. And if Schiit wants to send me some evaluation gear, I am happy to try their higher end offerings too, but for now, I'll keep saving up- The Gungnir and Mjolnir reviews will have to wait