Valhalla is a fully discrete, Class A, single-ended triode headphone amplifier with no overall feedback and noninverting circuit topology. It provides classic tube sound and can drive headphones with impedances as low as 32 ohms.
Pros - Buttery smooth unfatiguing tube sound; built like a tank.
Cons - Farts tube noise and possibly DC offset when 1st turned on...
I've owned an EarMax and Sennheiser HD 580's for 20 years, so I'm already familiar with tubed OTL headphone amps. The linestage of my old Quicksilver started developing some noise, and I didn't want to send it back, so I started using my EarMax as a simple linestage. This worked amazingly well, but made headphone listening inconvenient. When I saw that AudioAdvisor had one of these original Valhallas for $199.00, clearance, I couldn't resist.
My original plan was to use this unit for my yeoman line stage, and retire the EarMax back to headphone amp duty. Once I fired it up, it took all of 20 seconds to realize this was NOT a good plan.
This particular unit farts loud clicking as the tubes warm up. That's not so bad, but it seemed to be passing some DC offset, because the protection circuit of my Odyssey Kismet monoblocs kept engaging; the 1st this had ever happened. So, I turned the Valhalla off, replaced the EarMax as my linestage (which is always impeccably behaved), and made the Valhalla my headphone amp, as that's what it is designed for!
It took another 30 seconds of listening to find that this was a VERY good plan! Cut to the chase...buttery smooth, unfatigueing, but revealing triode sound at its best! With my 300 ohm HD 580's, this amp is even a better match than my EarMax. Highs are rolled off in absolute terms, but not so badly that you feel you're missing out on anything. Unbelievably smooth mids, powerful and quite tuneful bass. Buttloads of gain, very quiet for an all tube design. Probably not the best amp to pair with low impedance headphones; it is clear these tubes like being a voltage rather than a current source. Pair this amp with a 300 ohm or higher set of cans, you will NOT be disappointed. Tube farts aside, this amp STAYS! Whether you do classical, or grunge, this amp serves this music RIGHT. And as an aside, I have to note that the build quality of this amp is like a four figure headphone amp, not an entry level one. Unbelievable! Highly recommended. ONE CAVEAT:This amp does indeed pass DC when it is first turned on. So to save the drivers in your headphone, it is better to power it up 1st, then WAIT a MINUTE before you connect your cable. Same goes with powering down. Disconnect your headphone cable 1st, THEN power it down. You'll have no problems that way. FWIW, this amp does need some warm up time to sound its best. Don't even THINK about listening until the volume knob gets warm...that's when you can start. But the longer you leave it on, the better it sounds. That said, I'd not leave it on ALL the time, because you'll go thru your tubes too fast, that way.
Pros - releaxed yet capable treble, not overly warm/lush, timbre and neutrality, price, build quality,
Cons - excessive heat, diminishing returns,
After upgrading to the Valhalla, I thought I'd give it a review while comparing the lower end Magni that I upgraded from. Keep in mind these are all subjective thoughts, what may be a con for me may be a pro for you based on your preferences.
Non sound impressions: Build quality, as always, is excellent with Schiit. I can't find a single thing wrong with how it was constructed, it's solid, and even though it has a pretty compact size, it weighs a lot more than you would think. Compared to the Magni, it runs much, much hotter, but that is expected from a class A tube amplifier. The potentiometer works better on the Valhalla, it has less channel imbalance at lower volumes and is more precise than the Magni's potentiometer. The Magni's high gain seems to make the potentiometer almost useless, especially with low impedance headphones.
Bass: I can't notice any difference in the bass, they are both equal in impact and extension.
Midrange: The Valhalla adds a little more "meat" to the music and harshness is smoothed over. For example, Electric Guitars sound fuller, more laid back, and richer. The Magni sounds a bit thinner and brighter with the Electric guitar.
Treble: The Valhalla has less emphasis on sibilance and treble, however, the treble is still well extended and is there when needed, it doesn't sound overly warm or lush like a stereotypical tube amplifier. Cymbals and hi-hats still have a good sense of air and dominance, but the Magni renders them with a sharper, brighter tone. If you have been reading other reviews, the general consensus is that the Valhalla is actually quite bright for a tube amp, I agree. The Magni in comparison is a bit brighter, sharper, and more uncontrolled in the treble. However, the Magni can be much more exciting because of this, the downside is that it is more fatiguing and less forgiving of lower quality sources.
Soundstage: I don't notice much of a difference at all versus the Magni. The Valhalla sounds just a touch wider, deeper, and less in your head.
Song tests: (Source is a Schiit Modi, 320KB MP3s or FLACs, and a Sennheiser HD600)
Avenged Sevenfold, God Hates Us, Rock
Valhalla: Neutral and flatter. The Valhalla has more realistic timbre on the instrumentation versus the Magni. Magni: Brighter and more colored. The Magni has less realistic timbre on the guitars and drums, but, it is much more exciting. The guitars and drums are thinner and have more of a "pop/snap." The vocals, while more sibilant and sharper, are more exciting. Winner: None, tie. Do you prefer accuracy or an exciting sound?
Valhalla: Even though I was able to download this in a lossy format, this song isn't mastered too well, the Valhalla has less sibilance and everything is more laid back and lightly smoothed over with less peaks in the treble. Magni: Sibilance is more present, the Magni is not forgiving of the recording. The guitar at the end is a bit sharper with quicker decay, the tennis balls and respirator in the background are more prominent. Treble gets a bit peaky. Winner: Valhalla, much more smoother and forgiving.
Miles Davis, So What, Jazz
Valhalla: Towards the start, the drums on the right had less air and weren't as prominent on the Valhalla. When the trumpet abruptly starts at 1:29, the Valhalla sounded less sharp and didn't have as much glare. Good timbre on all the instruments as well. Once the trumpet goes crazy again at 3:25 on the left, the Valhalla once again sounds smoother, less sharp, and easier on the ears. Magni: Towards the start, the drums on the right had a bit more air and sounded a bit more dominant and in your face. When the trumpet abruptly starts at 1:29, the Magni
initially renders it with a sharper tone. Timbre is alright, but the Valhalla is ahead by a hair. Once the trumpet starts up at 3:25, the Magni again rendered it with a sharper than natural tone. Winner:Valhalla, better timbre and more controlled.
Snnop Dogg and The Doors, Riders on the Storm, Hip-hop/rap
Valhalla: The clapping in the beat is less prominent and has a slower decay (Fades away slower). Less sibilance and sharpness, sounds less in your head, but not by much. Magni: The clapping in the beat is more prominent and has a quicker decay (Faded away quicker). The Magni has slightly more sibilance and sounds more in your head, but again, not by much. Winner: Valhalla, more resolving in the soundstage and smoother.
A quick breakdown.
Bass impact/extension: Valhalla=Magni Mids: Valhalla>Magni Treble quantity: Valhalla<Magni Soundstage Depth/Width: Valhalla>Magni Timbre: Valhalla>Magni Detail:Valhalla=Magni (It can be argued that the Magni's treble exaggeration leads to fake detail perception, so I'm marking this as a tie.)
That about sums up my thoughts between the two amps. I must emphasize that the difference between the two is minimal, most of the differences I noticed was with critical listening and A/B testing. The reason why I only have four songs in the comparison is because in most songs, I really couldn't pinpoint much of a significant difference, other than "it sounds slightly less bright." The Valhalla is a diminishing return and it is not that much better than the Magni, in fact, on some songs it sounds even worse. I enjoyed the Magni with metal and rock, it had a more exciting and involving presentation, but, for the most part, the extra treble was unwelcome in most of my music. When I listened to lower quality music, I appreciated the Valhallas more forgiving nature. I also preferred the Valhalla for jazz, classical, and instrumentals for its more realistic timbre and pleasant tonality.
Pros - Tons of juice, good punch and control, beautiful midrange, dead quiet, good looks.
Cons - Nature of tubes, heat.
I used this amp mainly with a pair of HD 650 and it does what it is supposed to do: it has way more power than I need, it's quiet and it makes everything sound in its place. I have never heard other tube amps before, but I didn't get the "lushness" or the "tubey" thing , at all. It may be there, but it's just to tell you that if it is there, well, it's subtle. To my ear, this is neutral. I have no idea why exactly or how to explain it, but it has a "better" sound to me, more control, than my previous Fiio E10 and Aune T1 for what it's worth. Overall, a really good sounding product from my experience and I'm still enjoying it as much as the first day I got it.
Now for the bads... Well, if you ever thought about buying this amp, you are probably already aware of its "downsides". They don't lie on their website: this thing gets toasty. After a few hours, the volume knob gets really hot to the touch, but I don't care really. It takes arround 10 seconds for the amp to work when you power it on, and it takes like 10 minutes to completely power off. Tubes makes sounds (clicks) when they change temperature, but again, I couldn't care less.
If you read the previous paragraph correctly, you will understand that there is no real cons to this amp. In my book, this thing is a winner. It has the looks, it has the sound, it's made in USA, its 350$ and it has a killer warranty/customer support.
To be honest, if you asked me why I bought this amp over let say the Asgard 2 (or any other amp really), well I had a good price on my unit at the time as it was opened-box and the Asgard 2 wasn't available (and it ain't still) in a Canadian retailer. Would I buy the same amp today? Maybe yes, maybe no, but I would probably get a SS like the Asgard or a Violectric because they are more versatile. But do I regret my purchase? Absolutely not. For it's intended purpose, to power my HD650 on my desk at home, this thing gets the job done with flying colors.