Pros: Build quality, very transparent, sounds good with nearly everything, tons of power, detail, US built
Cons: may be slightly expensive to some
My first desktop amp I got was the Schiit Asgard. Can't believe I went so long with just weak portable amps. I bought the Asgard for the HD-600. Found it drove that perfectly, but made my K702 and K601 sound like poop. ATH-AD2000 also sounded bad too. D2000 however was pretty impressive on it. Went with the E9 and found I preferred the K702 on that, but still liked the Asgard for the HD-650.
My goal was to find an amp that sounds equally good with BOTH the HD-650 and the K702. I remember one night comparing all my amps for the HD-650 and it actually sounded the best out of my cheap Total Airhead. How the heck does that happen?! This was for gaming and music. This made me want to give the Micro Amp a try.
Pre-purchase impressions were that it's probably overpriced and can't possible be any better than what I already had. I always thought it was plastic, but it's definitely not. It's metal and rubber. You could throw it around the house and I bet it'd survive.
When I got the amp I was shocked at how small it was. It's tiny! It's about as long and wide as my wallet. Probably the height of two decks of cards. Without hearing it I thought I had maybe wasted my money on such a thing that couldn't possibly sound good. After spending a whole day with it that impression changed fast.
I was actually planning to take advantage of their 30 day trial. If it didn't get the pass I'd send it back immediately. Within the first day I found it to be a keeper.
The first impression upon listening is how much more powerful it seemed compared to the Asgard and my E9. This thing has zero problems driving the K400, K501, K601, Q701 or even any 600 ohm headphones that i've tried. I know this doesn't always mean much, but no headphone has ever been past 50% on the volume dial. K400 had to go the highest. My Sextett LP (600 ohm) only needs 30% on the volume dial. Q701 maybe around 40%.
I've found the signature very neutral. It won't radically change a headphones signature. I've found it to be very very slightly warm (comparable in warmth to my MSII perhaps). The bass is very accurate and doesn't magically add any bass, but does seem to improve it. I first noticed this with my Q701, KRK KNS-8400 and HD-600.
I've spent a year trying to figure out it's signature and it's tough because it doesn't seem like it has one. One reason I feel this way is that nearly everything sounds good from it. It won't suddenly make a headphone with forward upper mids sound even more aggressive in the mids than it already is. I had this idea once that it might have very slightly forward mids (maybe upper mids). So little that it's barely able to register with my ears. I'll have to test this further to see if it's my DAC or amp.
Bass heavy headphones also don't sound any more bassy. If anything, their bass is more controlled and less bloated sounding.
The treble on this amp is fairly smooth sounding. However It doesn't suddenly make any treble happy headphone easier on the ears. No treble roll off that i've heard. It doesn't take the edge off the K702 at all. I haven't heard a SS amp yet that can.
When I had the K702 for this, it seemed to kind of fill in the sound. Made them slightly more enjoyable to listen to and not quite as thin sounding. Slightly fuller sounding mids, but not like the Q701 has. The Micro Amp didn't make me keep the K702, but that'd be virtually impossible with any amp I think. I do think between the Airhead, Fiio E9 and Asgard, I liked the K702 from the Micro Amp the most.
I'm not a fan of the HD-650 at all, but it does many things very well. The Micro Amp was enough to push it further into the like category for me. I don't know if there's any amp that could make me love it. I think i'm just one of those who prefer the HD-598 or the HD-600. I generally hate headphones that are too warm. HD-650 is too warm (for me). I also don't like a laid back sound.
The build quality on this thing is excellent. It's built like a tank. It's metal and has rubber bumpers around the front and back. I'm sorry to say that i've dropped this thing no less than 4 times from a a height of around 4 feet. It's still working. It also does not function as an extra space heater like the Asgard!
Obviously I don't like the 3.55mm only jack, but it's not a big deal. I don't even know if it's possible for them to cram a 1/4" jack on this tiny thing.
I've also noticed this thing has a ton of detail. Combine it with a good DAC (HRT MSII is a nice pairing) and it seems to extract every bit of detail out of your songs. I've also found that every little change between cables (yes, i've said it) and DACs to be heard quite easily.
When switching between the E9 to the Micro Amp, the sound on the E9 from any headphone is a bit leaner and not as full sounding. Definitely a lot less detail. Supposedly they have the same op-amps (but Micro Amp has 7..no idea why), but they couldn't sound any more different. I don't know why, but my E9 seems to give every headphone an abnormally large sounstage. I don't know how or even if this is possible. On the Asgard, the K702's soundstage was so massive it made all background detail way too hard to hear. Almost like it went missing.
I need to compare this thing to the Matrix M-Stage. I bet the Micro Amp would be some serious competition for the M-Stage. My idea is that the M-Stage is more bassy, has a larger sounstage and less treble. Who knows. Has anyone compared both? I bet they sound somewhat similar.
The Micro Amp's soundstage (with proper recordings on the Q701) isn't abnormally large. Sometimes it seems a tiny bit smaller than my E9, but sometimes it's easy to be fooled. I kind of like to think the Soundstage of the Micro Amp is more accurate. When I get the M-Stage, i'll know for sure. When comparing them, it's not that much different in size. On the E9 it's a tiny bit wider. Again, could just be something fooling me. E9 seems to do that with all my headphones. No idea how.
I will say that with the K501, it's like a total out of head experience with the right music. Very impressive, but that's mostly due to the K501 and not just the amp. When I went into Tennpenny Tower in Fallout 3 with the K501, my jaw just about dropped. Felt like I was really there with all that elevator music surrounding me. K501's soundstage is too huge for gaming though.
I've found this to be also OK with most easier to drive headphones. When using my KRK KNS-8400 it doesn't ruin it's signature and just improves everything. The difference between the 8400 between unamped and driven with the Micro Amp + MS2 is quite impressive too. It actually almost sounds like a semi-open headphone. I would say the KRK KNS-8400 with this setup is comparable to the Q701, but maybe even better.
Despite being very slightly warm, it's not enough for some headphones to turn them from a cold and analytical detail monster to something that's very warm and easy on the ears. It can't even really help my Koss A/250 much in this area. I do however think it's enough to help the KRKs and Grados. Grado SR-225i and SRH-940 were quite good from the Micro Amp.
I think the Micro Amp is good for almost everything, but I would say it's slightly better for the AKG headphones than the Sennheisers, but just slightly. I've yet to find a headphone that sounds horrible from the Micro Amp. Even the 600 ohm DT-770 (bass light version) was great with it. I think the super easy to drive headphones or IEMs might be out of the question for this amp. I don't know and it's best to ask Headroom. I don't use it with any of my portables. DJ100 and KRK KNS-8400s seem OK. Same with my AD700/300.
The best headphones for the Micro Amp are the following:
AKG K601 (probably the best), K501, K702, Q701, KRK KNS-8400, HD-600/598/650, SRH-940, D2000, SA3000, SR-225i
On some headphones that benefit less from amping, there wasn't much change. I probably wouldn't buy the Micro Amp for just a K550 or HD-598. Somehow the KRKs and SRH-940 did seem to improve with the Micro Amp, which was a surprise. Even the soundstage got slightly larger. SRH-940 is a little more musical with the Micro Amp too.
So I've had this for quite awhile now. Felt it was 100% worth the $330. If it died, i'd immediately buy another. Basically loved every minute of using this thing. Don't let the looks and tiny size fool you, this thing is quite powerful and can probably drive anything.
BTW the version I have includes a huge brick power supply. Not a big deal for me. No plans on hauling this around.
I've discovered more about this amp in the last month than in an entire year. The reason I didn't like it so much with Sennheiser stuff is due to my DAC. I often would blame the amp, but the amp itself did NOT add ANY coloration that I could hear. Basically it should sound like what's connected to it with slight improvements. If I attach my Clip+ it will sound like a Clip+ with minor improvements. The nice thing is that you will hear what's connected and NOT your amp. I like this idea!
The slightly small soundstage for me was due to the source and not the amp. I only got a clue when I attached a full sized cd player to my Micro and magically got an improved soundstage.
I also have discovered that when connecting this to a Surge protector with filtering, it will bloat the bass and degrade the sound. It requires being connected directly to the wall. I was only able to verify this with my DJ100 closed headphones.
I've upgraded my DAC to an ODAC and now everything seems pretty dead neutral now. The Q701 has never sounded better. Exactly how it should sound, but even better.
I honestly can now not claim the Micro is bassy or has very slightly forward mids. Any coloration from the amp I can't really hear. Not enough for me to care.
Have to admit that out of all the audio gear i've ever bought, this is one of my favorites. I really like it that much. Any complaints i've had about it turned out to be due to an issue with the source!