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[size=medium]Review: Schiit Asgard & Avenson Audio Headphone Amp[/size]
[size=small]dynamic solid-state headphone amps[/size]
[size=small]www.schiit.com[/size]
[size=small]www.avensonaudio.com[/size]
[size=small]USA retail prices at press time:[/size]
[size=small]Asgard: $249[/size]
[size=small]Avenson HPA: $750[/size]
[size=small]published on: December 31, 2010[/size]
- download a printable 7-page PDF version of this review (right-click the link & save target)
- download a printable 5-page PDF version of the notes that were written for this review (right-click the link & save target). The notes contain much more detailed info broken down by individual CD tracks and will probably be worth reading for those seeking even more info to assist with a buying decision (or for those who merely want some insight into my reviewing process). The notes should be considered a supplement and not a replacement for this review (as the review is not straight from the notes) - I recommend reading this review first and then reading the notes.
Note: I will revisit this thread for only up to the next 14 days to answer any questions that might be posted and will not answer any questions past 14 days. Please do not send PMs at anytime as I will not respond.
Intro
As a fan of solid-state amps in general, American-made ones especially, Schiit Audio's Asgard caught my interest immediately when it came out earlier this year. As did the Avenson Audio Headphone Amp, which has been out since 2009 but I didn't discover it until just a couple of months ago. It always piques my interest even more when a manufacturer's Web site doesn't contain marketing-speak of vague & subjective sound-quality descriptions, but instead merely lists only specs, functions, and physical attributes. So inevitably I bought both of these amps - and what better way to check them out than to compare them to my personal benchmark amp, yet another American-made solid-state amp - the venerable HeadAmp Gilmore Lite? And incidentally enough, all three amps are high-current designs for low-impedance headphones - making for an interesting comparison indeed...
Reviewer Biases & Info
My view of a headphone system is "source first" followed by headphones and then amp. In other words, a source of highest quality possible (assuming recordings of high quality also) should be paired with the most preferential-sounding headphone(s), to be driven by the most technically optimal amp. In my view, the most technically optimal amp is the one that provides sufficient power for all headphones being used without inflecting its own sonic signature, or minimally at least.
Equipment Setup
- Source component: Plinius CD-101 (CD player) (power cord: Signal Cable Silver Resolution Reference - directly into wall)
- RCA interconnects: Analysis Plus Silver Oval
- Comparison headphone amp: HeadAmp Gilmore Lite (v2) w/ Elpac power supply
- Headphones: Audeze LCD-2, Audio-Technica AD2000 (re-cabled with APS V3), Beyerdynamic T1, Grado HP1000/HP2 (re-cabled with APS V3), Sennheiser HD800, Sony Qualia 010 (re-cabled with Moon Audio Black Dragon)
Evaluation Music
- Alison Krauss - Forget About It - "Ghost In This House", "It Don't Matter Now"
- Alison Krauss & Union Station - New Favorite - "Bright Sunny South"
- Alison Krauss & Union Station - Lonely Runs Both Ways - "This Sad Song"
- Dave Brubeck - Time Out [Legacy Edition] - "Blue Rondo a la Turk"
- Eva Cassidy - Live at Blues Alley - "Autumn Leaves"
- Global Communication - 76:14 - "9:39"
- Helloween - 7 Sinners - "Where The Sinners Go", "Who is Mr. Madman?"
- In Flames - The Jester Race - "Moonshield", "Artifacts of the Black Rain"
- Julia Fischer - Bach Concertos - "Concerto for two violins in D minor: Vivace (1st movement), Allegro (3rd movement)", "Violin Concerto in A minor: Allegro assai (3rd movement)"
- Katie Melua - Piece by Piece - "Shy Boy"
- Medeski Martin & Wood - Uninvisible - "Ten Dollar High"
- Megadeth - Countdown to Extinction [MFSL] - "Sweating Bullets", "This Was My Life"
- Nightwish - Once - "Wish I Had An Angel"
- Orbital - Snivilisation - "I Wish I Had Duck Feet", "Are We Here?"
- Pierre Boulez & Vienna Philharmonic Orchestra - Mahler Symphony #6 - "I. Allegro energico"
- Steve Kuhn - Mostly Coltrane - "Song of Praise"
- Symphony X - Paradise Lost - "Set the World on Fire", "Domination"
- The Crystal Method - Tweekend - "Murder", "Ten Miles Back"
- The Prodigy - The Fat of the Land - "Smack My Bitch Up", "Mindfields", "Narayan", "Fuel My Fire"
- Trifonic - Emergence - "Emergence", "Transgenic", "Sooner or Later"
- Weather Report - Heavy Weather - "A Remark You Made"
Customer Service
It'd be only fair to start with the subject of customer service for Schiit Audio, Avenson Audio, & HeadAmp Audio Electronics - these are businesses after all, and customer service is something that every business has to deal with.
I don't have any personal experience with Schiit Audio's customer service, but Jason Stoddard - who's a registered Member of the Trade (MOT) here on Head-Fi - seems to be prepared to cover this angle with the solid presence that he's quickly established on Head-Fi in the past months. He's been reliably answering questions that have been posted on the forums, handling any customer issues that have been reported, and providing product updates as well. I met him in person at Rocky Mountain Audio Fest 2010 and found him to be a really cool & easygoing guy, who clearly enjoys what he's doing. I'd say I'd have no qualms with dealing with Schiit Audio if I ever had to in the future.
Avenson Audio is another stand-up operation, and the main man behind it, Brad Avenson, also looks to be a solid type of guy - because I needed some service on the Headphone Amp when I first bought it, and he delivered at every step of the way. I won't provide details on what exactly needed service with the amp because it's not necessary - it was a minor thing and I don't think Mr. Avenson will likely be doing it again. His communication via e-mail was always quick and polite, and the entire process of the amp servicing was done flawlessly. Based on this experience, I wouldn't hesitate to deal with Avenson Audio again.
HeadAmp Audio Electronics' Justin Wilson isn't quite the same story as either Schiit or Avenson. Because I personally know Justin now and have met him many times at Head-Fi meets, I give him a lot of slack, mostly because I know how he operates and patience is usually key. I've bought from HeadAmp more than any other vendor on Head-Fi and if there's one thing that's always guaranteed from him, it's a high-quality final product - he has high standards when it comes to attention to detail, and I personally wouldn't have it any other way. But customer service is his weakest area, specifically accessibility, reliable communication, and timeliness, as has been reported time and again by many people on Head-Fi (and I've personally run into these issues too).
Operation, Handling, etc
Heat has been one of the most reported "issues" with the Schiit Asgard on Head-Fi, but during actual use the amp didn't get excessively hot. At full operating temperature, it's what I'd call toasty, primarily on the bottom and the sides. I found this heat annoying to deal with when inserting and removing RCA interconnects (which I often did for the purposes of this review to compare to the other amps), as inserting/removing interconnects invariably meant I had to hold the amp in place. Hence, I would recommend setting up the amp when it's powered off.
The Avenson HPA ran considerably cooler without any venting either, but on the other hand, it has obvious heatsinking on its sides. There were two quirks I ran into with the Avenson: (1) The RCA jacks are actually flipped from normal convention - most audio gear has the red Right channel input left-ward from the white (or black) Left channel input. On the Avenson, the red Right channel input is right-ward from the black Left channel input. Essentially this means you only have to swap the position of the Right and Left RCA interconnects when coupling to a digital source. (2) The Avenson HPA also has a mirror-polished aluminum chassis that catches fingerprints easily. The improved aesthetic makes it look very nice though.
Amp Recommendations Advice
As I routinely see people on Head-Fi eternally asking the question of which amp to buy - for their headphones, or music, or source, or whatever - I thought I'd add a short section here for my advice for folks who might be asking the same thing about the Asgard or Avenson HPA.
My opinion on the subject is that it doesn't really matter what you buy, and most people asking this question are vastly overthinking their buying decision. The three amps covered in this review are all designed for low-impedance, efficient headphones - and that info alone should be enough to guide your decision. If you don't own a headphone of that type, I would recommend looking at other amps (possibly a different type, like a tube or hybrid). It's true that most amps can drive a variety of headphone loads, and you can use a headphone on an amp it's not really optimal for anyway, but if you're seeking out optimal amp-headphone synergy, it makes the most amount of sense to match electrical characteristics. Low-impedance, efficient headphones typically demand high-current amps, and the Asgard, Avenson HPA, and Gilmore Lite are all prime examples of this type.
Moreover, there's really no need to spend too much time to think about which amp to buy when Schiit Audio has a 15-day return policy and Avenson Audio's dealers offer their own return policies (you can also buy direct but I'm not sure what sort of policy is offered). My recommendation is to just buy something and try it out. If you don't like something, either return it or sell it as used in the FS classifieds area on Head-Fi. Or you can buy used from the FS forums to save on cost.
Schiit Asgard
Most of my headphones were driven reasonably well by the Asgard but notable exceptions were the AKG K701 and Beyerdynamic T1. With the K701, it struggled to deliver clear-sounding music at very loud volume - not that high volume performance is necessarily an indicator of an amp's capability, but the K701 is unique in that it requires both high voltage and current levels to maintain clarity and low-frequency energy. I've found that the K701's relationship to effective amplification is how it sounds at a very loud volume - and the Asgard is just one of many amps that I've heard become "blurry"-sounding at high volume with the K701. The T1 responded differently but it was clear it wasn't adequately driven either, with a loss in musical dynamics (contrasting soft vs loud) and low-frequency energy.
It was only after extended swapping out between all three amps that I started "getting" the Asgard's sound, which was initially tricky to figure out. There were a variety of deficiencies I noticed. Versus the Gilmore Lite, it lacked razor-like treble and a properly fast "speed". It's not that it blurred over very fast sequences (well it did, but just a tiny bit), it felt more like it was playing a game of catch-up. On very fast runs in metal music, like the speedruns in both Helloween's "Who is Mr. Madman?" and Megadeth's "Sweating Bullets", the Asgard just didn't maintain the same pacing as the GL, as it sounded like the speed of the drumming was too fast for it to track. In the aspect of treble, the Asgard certainly had a good quantity, but compared to the GL it just wasn't as clean/clear, one of the best examples being the duck feet-raindrops-warbling transition of Orbital's "I Wish I Had Duck Feet". The GL made this transition sound so clean and clear, it was obvious where one was phasing out and the next one was starting, but on the Asgard it was less obvious and less clean around the edges. I guess it could be said that the Asgard was simply a "slower" amp than the GL overall - not only did it tend to lose pacing of extremely fast note sequences, it also sounded a bit plodgy on percussion-like effects and bass notes.
If there was one headphone that benefitted the most from the Asgard sonically, it was my Grado HP1000. As it turned out, the Asgard had the most laterally wide soundstage of the three amps with the most amount of air & space between instruments, which particularly helped out the HP1000 because of its intrinsically compressed soundstage (in terms of both width & depth). The added z-axis depth of the Asgard also improved the "shallowness" of the HP1K's soundstage for both classical- and jazz-type music so that the virtual musicians didn't sound too close or forward (as tends to happen on the HP1K). The Asgard definitely did some "displacement" that was an appreciated added quality on the HP1K.
I can't say that the Asgard really worked sonically for my other headphones though - it just didn't seem like the ideal sonic match for the AD2K, HD800, or Qualia. The "slow" quality subtracted from the AD2K's impulse response and it didn't exactly help to fill in any mid-range or offset any of the treble on the HD800 or Qualia either. For example, it didn't add any fullness or body to vocals or instruments like piano, sax, trumpets, or acoustic/electric guitars and it certainly didn't contribute any added "thrash" to the electric guitars in metal music, in either frequency direction (towards the mid-bass or the treble). More than anything this made the amp sound "boring" and even almost "dead" - the lack of mid-range body seemed to take away a degree of life/presence, and there wasn't enough upper treble quantity to highlight the "electricity" of electric guitars enough either. I think the lack of emphasis at any one part of the frequency spectrum (be it the bass, mid-range, or treble) was what made the Asgard sound flat/boring to me, and this quality came across regardless of which headphones were used. I guess one could say that the Asgard has a good balanced sound, but to me it came off as generic, unspectacular, & boring, and I'd sooner recommend one of the other amps for something more exciting with a definite frequency skew - like the Avenson (which skewed towards the bass) or the Gilmore Lite (treble). (I'd place the Asgard somewhere in between.)
Avenson Headphone Amp
One of the first conclusions I came to with the Avenson was that it was definitely the better amp for the Audeze LCD-2 over both the Asgard and Gilmore Lite. The Asgard's "dead/boring" sound did no favors for the LCD-2, and the GL seemed to just lack something (most likely sufficient power output, but this is just a guess). The Avenson was the only amp that drove the LCD-2 to loud volumes without sounding strained. It delivered a solid bass foundation into the LCD-2 with a good amount of "assertiveness" in the mid-bass & mid-range that made it the most direct- and "fun"-sounding for metal music. The Avenson also capably drove the T1 where the Asgard couldn't, with moderate dynamics and strong mid-bass impact. The T1 sounded surprisingly good on this amp, about on level with the Rockhopper M3 that I also own with a similar type of direct sound that closed up the soundstage a bit, which worked well for rock/metal-type music. More than that, the Avenson helped the T1 engage bass/mid-bass forcefully with a visceral sense of power and drive.
In fact, probably the best quality of the Avenson was its overall mid-range/mid-bass-skewed sound and its inflection on the mid-range in particular. If there was one thing that consistently stood out about the Avenson, it was the full-bodied (almost thick, even) mid-range that really added a lot to a variety of music genres. It was particularly good at displaying an authoritative power into the mid-bass in general with strong depth and force that was actually sort of addictive on the metal music by In Flames and Helloween. Drums in particular sounded physical, low, and powerful. The Avenson also "ripped" guitars really well towards the mid-bass direction so that they sounded especially low and full. Essentially, this amp never failed to provide a sense that it was practically setting up the band almost right in-your-face with the guitars especially sounding close-up and assaulting.
The Avenson wasn't just a one-trick pony with metal music though (as awesome as that was), as it also worked nicely on classical and jazz - well, depending on headphone of course. The Avenson had a bold, rich tone on sweeping violins that ended up sounding more realistic than the competing Asgard, which made them sound wispy more than anything else. It was also more dynamic with more intensity & volume modulation than the Asgard and better conveyed a sense that violin bows were actually sweeping across the strings. And with jazz, the Avenson's fuller mid-range had the expected effect of really bringing out instruments like trumpet and sax - for example doing an excellent job with the sax on Steve Kuhn's "Song of Praise," bringing it close into the jazz group and enhancing the "soul" of the instrument. Piano also sounded appropriately heavy on the Avenson - like an instrument of large size, which it is.
It's a testament to the capability of the Avenson when I say that it drove every headphone I own effectively (including the LCD-2, HD800, and T1), and never sounding like it was straining, even at high volumes. But of course no amp is perfect in all aspects and the Avenson had a few weak spots. The one most noticeable to me was a general lack of clarity - multi-layer music was never truly clear-sounding and there was always a sense of a bit of murkiness & indistinction. It didn't have a whole lot of treble quantity either, definitely going towards the "smooth treble" direction as opposed to edgy & sharp (like the Gilmore Lite). And its soundstage was unusually compacted in width and depth. On headphones like the LCD-2 and HP1000, this made the music sound especially small-scale. It was a better effect on the HD800 and T1 though, as the forced reduction in size made them both sound more realistic. Finally, the Avenson didn't have a completely fast impulse response and trailed behind the GL a bit, but only by a little. This only affected minor timing cues on percussion instruments that was most noticeable with the AD2K.
Gilmore Lite
As this amp is the most known of the three on Head-Fi, it made sense to use it as a baseline against the Asgard and Avenson HPA. This amp is my personal benchmark for a variety of reasons. It has the fastest impulse response I've ever heard from a budget-oriented amp: it can track extremely fast notes (or events otherwise) running throughout the music, ranging from events like fast drumming (the GL will "hit" every single drum impact and will do it with controlled power) to blink-and-you-miss-it impacts/outbursts of any type (kettle drums, popping, cracking, etc). The GL can also "power through" heavy bass like it's Superman and nothing could possibly block its way or slow it down. It's also the clearest-, cleanest-sounding amp I've heard - nothing hazy, murky, blurry, undefined, or indistinct about it, it just exposes everything in the mix - and how much of the mix is heard is affected by only the source component & headphones. And its treble isn't smoothed over like on so many other amps - it's just pure & pristine, and it won't sound like anything less than that unless either the source component or headphones smoothens it over.
That's my opinion of the Gilmore Lite - but it's not perfect either. It's not really able to drive a wide variety of headphone loads and tends to wimp out with high-impedance, inefficient headphones (cases in point, HD800 and T1). Its soundstage translation isn't ideal either - it can convey proper width, but it has a lack of depth that tends to make music sound 2D instead of 3D. And a lot of people would probably think it's recessed in the mid-range, mid-bass, & bass - the mid-range is more on the "thin" side of things and the bass/mid-bass area gravitates more towards a bass "extension" quality more than bass "force/weight/power".
Summary
If I came across as too harsh on the Schiit Asgard, that was on purpose. I just wasn't very impressed by it sonically, at least with my headphones. It's possible it'd be better paired with other headphones - I suspect the Senn HD6x0 models for starters.
I was more impressed by the Avenson Headphone Amp despite its weaknesses, and I think it's a prime solution for most people looking for an amp that can drive both low-impedance and high-impedance headphones. It performed fairly well and its price isn't too bad either.
[size=small]dynamic solid-state headphone amps[/size]
[size=small]www.schiit.com[/size]
[size=small]www.avensonaudio.com[/size]
[size=small]USA retail prices at press time:[/size]
[size=small]Asgard: $249[/size]
[size=small]Avenson HPA: $750[/size]
[size=small]published on: December 31, 2010[/size]
- download a printable 7-page PDF version of this review (right-click the link & save target)
- download a printable 5-page PDF version of the notes that were written for this review (right-click the link & save target). The notes contain much more detailed info broken down by individual CD tracks and will probably be worth reading for those seeking even more info to assist with a buying decision (or for those who merely want some insight into my reviewing process). The notes should be considered a supplement and not a replacement for this review (as the review is not straight from the notes) - I recommend reading this review first and then reading the notes.
Note: I will revisit this thread for only up to the next 14 days to answer any questions that might be posted and will not answer any questions past 14 days. Please do not send PMs at anytime as I will not respond.
Intro
As a fan of solid-state amps in general, American-made ones especially, Schiit Audio's Asgard caught my interest immediately when it came out earlier this year. As did the Avenson Audio Headphone Amp, which has been out since 2009 but I didn't discover it until just a couple of months ago. It always piques my interest even more when a manufacturer's Web site doesn't contain marketing-speak of vague & subjective sound-quality descriptions, but instead merely lists only specs, functions, and physical attributes. So inevitably I bought both of these amps - and what better way to check them out than to compare them to my personal benchmark amp, yet another American-made solid-state amp - the venerable HeadAmp Gilmore Lite? And incidentally enough, all three amps are high-current designs for low-impedance headphones - making for an interesting comparison indeed...
Reviewer Biases & Info
My view of a headphone system is "source first" followed by headphones and then amp. In other words, a source of highest quality possible (assuming recordings of high quality also) should be paired with the most preferential-sounding headphone(s), to be driven by the most technically optimal amp. In my view, the most technically optimal amp is the one that provides sufficient power for all headphones being used without inflecting its own sonic signature, or minimally at least.
Equipment Setup
- Source component: Plinius CD-101 (CD player) (power cord: Signal Cable Silver Resolution Reference - directly into wall)
- RCA interconnects: Analysis Plus Silver Oval
- Comparison headphone amp: HeadAmp Gilmore Lite (v2) w/ Elpac power supply
- Headphones: Audeze LCD-2, Audio-Technica AD2000 (re-cabled with APS V3), Beyerdynamic T1, Grado HP1000/HP2 (re-cabled with APS V3), Sennheiser HD800, Sony Qualia 010 (re-cabled with Moon Audio Black Dragon)
Evaluation Music
- Alison Krauss - Forget About It - "Ghost In This House", "It Don't Matter Now"
- Alison Krauss & Union Station - New Favorite - "Bright Sunny South"
- Alison Krauss & Union Station - Lonely Runs Both Ways - "This Sad Song"
- Dave Brubeck - Time Out [Legacy Edition] - "Blue Rondo a la Turk"
- Eva Cassidy - Live at Blues Alley - "Autumn Leaves"
- Global Communication - 76:14 - "9:39"
- Helloween - 7 Sinners - "Where The Sinners Go", "Who is Mr. Madman?"
- In Flames - The Jester Race - "Moonshield", "Artifacts of the Black Rain"
- Julia Fischer - Bach Concertos - "Concerto for two violins in D minor: Vivace (1st movement), Allegro (3rd movement)", "Violin Concerto in A minor: Allegro assai (3rd movement)"
- Katie Melua - Piece by Piece - "Shy Boy"
- Medeski Martin & Wood - Uninvisible - "Ten Dollar High"
- Megadeth - Countdown to Extinction [MFSL] - "Sweating Bullets", "This Was My Life"
- Nightwish - Once - "Wish I Had An Angel"
- Orbital - Snivilisation - "I Wish I Had Duck Feet", "Are We Here?"
- Pierre Boulez & Vienna Philharmonic Orchestra - Mahler Symphony #6 - "I. Allegro energico"
- Steve Kuhn - Mostly Coltrane - "Song of Praise"
- Symphony X - Paradise Lost - "Set the World on Fire", "Domination"
- The Crystal Method - Tweekend - "Murder", "Ten Miles Back"
- The Prodigy - The Fat of the Land - "Smack My Bitch Up", "Mindfields", "Narayan", "Fuel My Fire"
- Trifonic - Emergence - "Emergence", "Transgenic", "Sooner or Later"
- Weather Report - Heavy Weather - "A Remark You Made"
Customer Service
It'd be only fair to start with the subject of customer service for Schiit Audio, Avenson Audio, & HeadAmp Audio Electronics - these are businesses after all, and customer service is something that every business has to deal with.
I don't have any personal experience with Schiit Audio's customer service, but Jason Stoddard - who's a registered Member of the Trade (MOT) here on Head-Fi - seems to be prepared to cover this angle with the solid presence that he's quickly established on Head-Fi in the past months. He's been reliably answering questions that have been posted on the forums, handling any customer issues that have been reported, and providing product updates as well. I met him in person at Rocky Mountain Audio Fest 2010 and found him to be a really cool & easygoing guy, who clearly enjoys what he's doing. I'd say I'd have no qualms with dealing with Schiit Audio if I ever had to in the future.
Avenson Audio is another stand-up operation, and the main man behind it, Brad Avenson, also looks to be a solid type of guy - because I needed some service on the Headphone Amp when I first bought it, and he delivered at every step of the way. I won't provide details on what exactly needed service with the amp because it's not necessary - it was a minor thing and I don't think Mr. Avenson will likely be doing it again. His communication via e-mail was always quick and polite, and the entire process of the amp servicing was done flawlessly. Based on this experience, I wouldn't hesitate to deal with Avenson Audio again.
HeadAmp Audio Electronics' Justin Wilson isn't quite the same story as either Schiit or Avenson. Because I personally know Justin now and have met him many times at Head-Fi meets, I give him a lot of slack, mostly because I know how he operates and patience is usually key. I've bought from HeadAmp more than any other vendor on Head-Fi and if there's one thing that's always guaranteed from him, it's a high-quality final product - he has high standards when it comes to attention to detail, and I personally wouldn't have it any other way. But customer service is his weakest area, specifically accessibility, reliable communication, and timeliness, as has been reported time and again by many people on Head-Fi (and I've personally run into these issues too).
Operation, Handling, etc
Heat has been one of the most reported "issues" with the Schiit Asgard on Head-Fi, but during actual use the amp didn't get excessively hot. At full operating temperature, it's what I'd call toasty, primarily on the bottom and the sides. I found this heat annoying to deal with when inserting and removing RCA interconnects (which I often did for the purposes of this review to compare to the other amps), as inserting/removing interconnects invariably meant I had to hold the amp in place. Hence, I would recommend setting up the amp when it's powered off.
The Avenson HPA ran considerably cooler without any venting either, but on the other hand, it has obvious heatsinking on its sides. There were two quirks I ran into with the Avenson: (1) The RCA jacks are actually flipped from normal convention - most audio gear has the red Right channel input left-ward from the white (or black) Left channel input. On the Avenson, the red Right channel input is right-ward from the black Left channel input. Essentially this means you only have to swap the position of the Right and Left RCA interconnects when coupling to a digital source. (2) The Avenson HPA also has a mirror-polished aluminum chassis that catches fingerprints easily. The improved aesthetic makes it look very nice though.
Amp Recommendations Advice
As I routinely see people on Head-Fi eternally asking the question of which amp to buy - for their headphones, or music, or source, or whatever - I thought I'd add a short section here for my advice for folks who might be asking the same thing about the Asgard or Avenson HPA.
My opinion on the subject is that it doesn't really matter what you buy, and most people asking this question are vastly overthinking their buying decision. The three amps covered in this review are all designed for low-impedance, efficient headphones - and that info alone should be enough to guide your decision. If you don't own a headphone of that type, I would recommend looking at other amps (possibly a different type, like a tube or hybrid). It's true that most amps can drive a variety of headphone loads, and you can use a headphone on an amp it's not really optimal for anyway, but if you're seeking out optimal amp-headphone synergy, it makes the most amount of sense to match electrical characteristics. Low-impedance, efficient headphones typically demand high-current amps, and the Asgard, Avenson HPA, and Gilmore Lite are all prime examples of this type.
Moreover, there's really no need to spend too much time to think about which amp to buy when Schiit Audio has a 15-day return policy and Avenson Audio's dealers offer their own return policies (you can also buy direct but I'm not sure what sort of policy is offered). My recommendation is to just buy something and try it out. If you don't like something, either return it or sell it as used in the FS classifieds area on Head-Fi. Or you can buy used from the FS forums to save on cost.
Schiit Asgard
Most of my headphones were driven reasonably well by the Asgard but notable exceptions were the AKG K701 and Beyerdynamic T1. With the K701, it struggled to deliver clear-sounding music at very loud volume - not that high volume performance is necessarily an indicator of an amp's capability, but the K701 is unique in that it requires both high voltage and current levels to maintain clarity and low-frequency energy. I've found that the K701's relationship to effective amplification is how it sounds at a very loud volume - and the Asgard is just one of many amps that I've heard become "blurry"-sounding at high volume with the K701. The T1 responded differently but it was clear it wasn't adequately driven either, with a loss in musical dynamics (contrasting soft vs loud) and low-frequency energy.
It was only after extended swapping out between all three amps that I started "getting" the Asgard's sound, which was initially tricky to figure out. There were a variety of deficiencies I noticed. Versus the Gilmore Lite, it lacked razor-like treble and a properly fast "speed". It's not that it blurred over very fast sequences (well it did, but just a tiny bit), it felt more like it was playing a game of catch-up. On very fast runs in metal music, like the speedruns in both Helloween's "Who is Mr. Madman?" and Megadeth's "Sweating Bullets", the Asgard just didn't maintain the same pacing as the GL, as it sounded like the speed of the drumming was too fast for it to track. In the aspect of treble, the Asgard certainly had a good quantity, but compared to the GL it just wasn't as clean/clear, one of the best examples being the duck feet-raindrops-warbling transition of Orbital's "I Wish I Had Duck Feet". The GL made this transition sound so clean and clear, it was obvious where one was phasing out and the next one was starting, but on the Asgard it was less obvious and less clean around the edges. I guess it could be said that the Asgard was simply a "slower" amp than the GL overall - not only did it tend to lose pacing of extremely fast note sequences, it also sounded a bit plodgy on percussion-like effects and bass notes.
If there was one headphone that benefitted the most from the Asgard sonically, it was my Grado HP1000. As it turned out, the Asgard had the most laterally wide soundstage of the three amps with the most amount of air & space between instruments, which particularly helped out the HP1000 because of its intrinsically compressed soundstage (in terms of both width & depth). The added z-axis depth of the Asgard also improved the "shallowness" of the HP1K's soundstage for both classical- and jazz-type music so that the virtual musicians didn't sound too close or forward (as tends to happen on the HP1K). The Asgard definitely did some "displacement" that was an appreciated added quality on the HP1K.
I can't say that the Asgard really worked sonically for my other headphones though - it just didn't seem like the ideal sonic match for the AD2K, HD800, or Qualia. The "slow" quality subtracted from the AD2K's impulse response and it didn't exactly help to fill in any mid-range or offset any of the treble on the HD800 or Qualia either. For example, it didn't add any fullness or body to vocals or instruments like piano, sax, trumpets, or acoustic/electric guitars and it certainly didn't contribute any added "thrash" to the electric guitars in metal music, in either frequency direction (towards the mid-bass or the treble). More than anything this made the amp sound "boring" and even almost "dead" - the lack of mid-range body seemed to take away a degree of life/presence, and there wasn't enough upper treble quantity to highlight the "electricity" of electric guitars enough either. I think the lack of emphasis at any one part of the frequency spectrum (be it the bass, mid-range, or treble) was what made the Asgard sound flat/boring to me, and this quality came across regardless of which headphones were used. I guess one could say that the Asgard has a good balanced sound, but to me it came off as generic, unspectacular, & boring, and I'd sooner recommend one of the other amps for something more exciting with a definite frequency skew - like the Avenson (which skewed towards the bass) or the Gilmore Lite (treble). (I'd place the Asgard somewhere in between.)
Avenson Headphone Amp
One of the first conclusions I came to with the Avenson was that it was definitely the better amp for the Audeze LCD-2 over both the Asgard and Gilmore Lite. The Asgard's "dead/boring" sound did no favors for the LCD-2, and the GL seemed to just lack something (most likely sufficient power output, but this is just a guess). The Avenson was the only amp that drove the LCD-2 to loud volumes without sounding strained. It delivered a solid bass foundation into the LCD-2 with a good amount of "assertiveness" in the mid-bass & mid-range that made it the most direct- and "fun"-sounding for metal music. The Avenson also capably drove the T1 where the Asgard couldn't, with moderate dynamics and strong mid-bass impact. The T1 sounded surprisingly good on this amp, about on level with the Rockhopper M3 that I also own with a similar type of direct sound that closed up the soundstage a bit, which worked well for rock/metal-type music. More than that, the Avenson helped the T1 engage bass/mid-bass forcefully with a visceral sense of power and drive.
In fact, probably the best quality of the Avenson was its overall mid-range/mid-bass-skewed sound and its inflection on the mid-range in particular. If there was one thing that consistently stood out about the Avenson, it was the full-bodied (almost thick, even) mid-range that really added a lot to a variety of music genres. It was particularly good at displaying an authoritative power into the mid-bass in general with strong depth and force that was actually sort of addictive on the metal music by In Flames and Helloween. Drums in particular sounded physical, low, and powerful. The Avenson also "ripped" guitars really well towards the mid-bass direction so that they sounded especially low and full. Essentially, this amp never failed to provide a sense that it was practically setting up the band almost right in-your-face with the guitars especially sounding close-up and assaulting.
The Avenson wasn't just a one-trick pony with metal music though (as awesome as that was), as it also worked nicely on classical and jazz - well, depending on headphone of course. The Avenson had a bold, rich tone on sweeping violins that ended up sounding more realistic than the competing Asgard, which made them sound wispy more than anything else. It was also more dynamic with more intensity & volume modulation than the Asgard and better conveyed a sense that violin bows were actually sweeping across the strings. And with jazz, the Avenson's fuller mid-range had the expected effect of really bringing out instruments like trumpet and sax - for example doing an excellent job with the sax on Steve Kuhn's "Song of Praise," bringing it close into the jazz group and enhancing the "soul" of the instrument. Piano also sounded appropriately heavy on the Avenson - like an instrument of large size, which it is.
It's a testament to the capability of the Avenson when I say that it drove every headphone I own effectively (including the LCD-2, HD800, and T1), and never sounding like it was straining, even at high volumes. But of course no amp is perfect in all aspects and the Avenson had a few weak spots. The one most noticeable to me was a general lack of clarity - multi-layer music was never truly clear-sounding and there was always a sense of a bit of murkiness & indistinction. It didn't have a whole lot of treble quantity either, definitely going towards the "smooth treble" direction as opposed to edgy & sharp (like the Gilmore Lite). And its soundstage was unusually compacted in width and depth. On headphones like the LCD-2 and HP1000, this made the music sound especially small-scale. It was a better effect on the HD800 and T1 though, as the forced reduction in size made them both sound more realistic. Finally, the Avenson didn't have a completely fast impulse response and trailed behind the GL a bit, but only by a little. This only affected minor timing cues on percussion instruments that was most noticeable with the AD2K.
Gilmore Lite
As this amp is the most known of the three on Head-Fi, it made sense to use it as a baseline against the Asgard and Avenson HPA. This amp is my personal benchmark for a variety of reasons. It has the fastest impulse response I've ever heard from a budget-oriented amp: it can track extremely fast notes (or events otherwise) running throughout the music, ranging from events like fast drumming (the GL will "hit" every single drum impact and will do it with controlled power) to blink-and-you-miss-it impacts/outbursts of any type (kettle drums, popping, cracking, etc). The GL can also "power through" heavy bass like it's Superman and nothing could possibly block its way or slow it down. It's also the clearest-, cleanest-sounding amp I've heard - nothing hazy, murky, blurry, undefined, or indistinct about it, it just exposes everything in the mix - and how much of the mix is heard is affected by only the source component & headphones. And its treble isn't smoothed over like on so many other amps - it's just pure & pristine, and it won't sound like anything less than that unless either the source component or headphones smoothens it over.
That's my opinion of the Gilmore Lite - but it's not perfect either. It's not really able to drive a wide variety of headphone loads and tends to wimp out with high-impedance, inefficient headphones (cases in point, HD800 and T1). Its soundstage translation isn't ideal either - it can convey proper width, but it has a lack of depth that tends to make music sound 2D instead of 3D. And a lot of people would probably think it's recessed in the mid-range, mid-bass, & bass - the mid-range is more on the "thin" side of things and the bass/mid-bass area gravitates more towards a bass "extension" quality more than bass "force/weight/power".
Summary
If I came across as too harsh on the Schiit Asgard, that was on purpose. I just wasn't very impressed by it sonically, at least with my headphones. It's possible it'd be better paired with other headphones - I suspect the Senn HD6x0 models for starters.
I was more impressed by the Avenson Headphone Amp despite its weaknesses, and I think it's a prime solution for most people looking for an amp that can drive both low-impedance and high-impedance headphones. It performed fairly well and its price isn't too bad either.
