This is a review and detailed measurements of the Schiit Valhalla 2 headphone amplifier. It is on kind loan from a member. The Valhalla 2 costs US $349 from Schiit itself.I recently measured the older and discontinued Schiit Valhalla . This is what Schiit says about the improvements:As you can imagine, the look and feel of the Valhalla 2 is almost identical to other Schiit units:The volume control is large and feels good.I am not going to bother showing you the back as it is just a input and RCA outs mirroring the headphone out. And built-in mains power supply.The Valhalla had the worse distortion metric of any headphone amplifier I have tested. Has the Valhalla improved? Let's find out.I set the unit to low gain, fed it 2 volt and matched the volume to produce the same:We have a nice step up in performance. SINAD (signal over noise and distortion) is up to nearly 80 dB in good channel versus just 44 dB with the original Valhalla. Second harmonic dominates as it did there.Mains hum and buzz introduces but is not dominant enough to impact the measurements of SINAD. Playing with grounding made no difference. And oh, I checked and the chassis is properly grounded to mains earth/safety terminal.We have channel mismatch of about 0.5 dB which seems to be typical of a lot of these tube products.The improved SINAD lifts the status of Schiit Valhalla tube amp to nearly that of Lyr 2:Frequency response is flat in audible band which is good:Signal to noise ratio is good at full volume but drops precipitously at 50 millivolt output:So likely the Valhalla 2 will be a buzz and hum factory with high efficiency IEMs.Digging further into distortion using intermodulation signal pairs of 60 Hz and 7 kHz we get:Dominant impairment is distortion and it rises at less than 1 millivolt and climbs from there.32-tone version produces this:We have decent gap between distortion and signal peak of 85 dB. That is quite a bit better than 70 dB we got with the Little Dot MK II headphone amplifier THD+N vs frequency shows constant level of distortion or noise:Most important data is the amount of power relative to distortion so let's go there with 300 ohm load:Depending on where you stop on the rising distortion curve, there is fair amount of power as is typically the case with tube amplifiers.Switching to 33 ohm load though, shows dismal output power ratings and distortion:Channel imbalance with respect to volume control position is good:Since there is no output transformer, Schiit must be using an output capacitor and hence, its output impedance is frequency dependent:As noted, there is also dependency on gain setting. In low gain, there is half as much output impedance. With high gain, you are likely to get some frequency response variations depending on the frequency dependent impedance of your headphone.Using my Hifiman HE-400i with its low impedance immediately showed the weakness of such tube designs with inability to drive much current. While you could get reasonable sound at lower volume levels, as you got close to maximum volume the bass got heavily distorted. So definitely avoid this amplifier if you have a low impedance headphone.With the much higher impedance Sennheiser HD-650 headphones, the situation changes as well as it did with the original Schiit Valhalla. There was plenty of power here. I could detect some rise in distortion though above about 2:00 o'clock on the volume control with the highs getting exaggerated. But that was pretty loud and would not be normal listening level.I detected no fidelity improvements in my listening tests over solid state amplifiers.The clean up of the design in Schiit Valhalla 2 over the original is quite obvious in measurements. Alas, at the end of the day it is still a tube product with ability to drive high output impedance headphone. Lower impedance headphones are just not suitable to it and Schiit stating otherwise is misleading.Subjectively, the sound is fine with high impedance headphones. But why bother when you can get a solid state headphone amplifier that drives high and low impedance headphones equally well?If you are itching to have a tube headphone amplifier, the Schiit Valhalla 2 at $350 seems like a good option. It won't get my recommendation with this type of performance but you have already ignored my advice in wanting a tube amp anyway.-------As always, questions, comments, recommendations, etc. are welcome.Please support reviews like this by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/