Magni 3+ vs Magni Heresy vs Asgard 2
I tested the three units informally using a few well-known-to-me Classical and mostly acoustic selections. (source was re-purposed dvd player with coax s/pdif -> Bifrost MB (original gen) -> test amp (in high-gain mode) -> AKG K702 -> my ears). All three amps were left on 24 hours prior, and kept on, except powered down briefly to change cabling, then powered back up for 2 mins before resuming listening, typically by listening to a few tracks, then changing to another amp. I listen at lower levels than most.
The 3 Schiit HP Amps were also compared with a late-80's vintage Aragon 18K pre-amp (external PSU re-capped using Panasonic TSU / FC / FM series low-impedance caps, remainder of Aragon is stock) and generic dual RCA to TRS adapter cable to drive the same AKGs.
K702's are rated around 62 ohms and good efficiency for dynamic over-the-ear phones, so easy to drive for all 3 Schiit amps.
To my ears, the Asgard 2 was the winner amongst the Schiit Amps (no surprise, as it has the highest MSRP and therefore a bigger parts budget, including the larger transformer at 30VA, more filter capacitance, the Alps RK27 "blue velvet" pot, and beefy output transistors)
soundstage: Aragon 18K > Asgard 2 > Magni 3+ >= Magni Heresy.
Bass extension and slam: Magni 3+ = Magni Heresy >= Asgard 2 > Aragon 18K
Power: Magni 3+ = Magni Heresy > Asgard 2 ~ Aragon 18K (but any of them have enough power into the K702 to drive above rated max SPL)
Smoothness: Magni Heresy is smoother sounding than Magni 3+, but also a bit less detailed.
Bottom Line recommendations: for a budget amp that can drive low-impedance inefficient headphones (e.g. Audeze LCD1, some Hifi-Man) the Magni 3 series seems like a good fit. If you can afford the additional cost, and soundstage and imaging are important to YOU, then I recommend stepping up to the Asgard 2 (currently on closeout) or Asgard 3 (which I have not heard yet). For the low impedance planars (10~25 ohms) the Asgard 2 will not play as loud as the Magni 3's or the Asgard 3.
disclosures: I don't work for Schiit, but have an electronics engineering background. I believe that specifications (at least those measurements currently specified with audio equipment) don't always correlate with perceived sound quality. Bifrost MB and Asgard 2 were purchased in 2019 (BEFORE they were available at special Classic-Stack pricing
The Magni 3+ and Magni Heresy were provided by
@Jason Stoddard free (as a courtesy for answering the "engineer's quiz", as another HF member also did, who also received a free set of these amps too).
Jason, thanks again for the Magni 3's. I was most surprised at the performance of the Heresy, given that it's output stage uses multiple parallel-connected op-amps (designed for small signal use, but have reasonably low open-loop output impedance). Looking forward to a next gen solid state amp that can drive planars (aka medium-high standing bias + continuity) but imaging and soundstage as good as the Aragon 18K.