I will make this brief.
I have listened to the amp now for about a day or so; during that time I have noticed little or no change of sonic characteristics from break-in except perhaps a slight increase in dynamic headroom.
The associated equipment: I have a computer setup and an all-in-one player attached to the MOH right now. Also an airhead. I know, it's unfair comparing this baby to the airhead, but I need to establish a point of reference. This is my first great venture into the super high end world of headphone amplification.
The computer is one I built myself from scratch, 2.4ghz 533fsb, 512MB GeIL DDR350, and so on and so forth. It has a turtle beach santa cruz soundcard. I connect this to the amp with a Kimber 1/8" to RCA 6 foot cable.
The player is a Sony DVP-NS500V which is hooked up with Dimarzio M-Path 1 meter interconnects.
I have done 90% of my listening through my SACD/DVD/CD player. The computer setup is mainly used for gaming and casual previewing of songs before purchasing a CD.
I have done 95% of my listening with crossfeed on. I don't listen to headphones without crossfeed because the image is messed up and the resulting layering of voices results imho in a loss of realism and even detail.
The characteristics of this amp are as follows:
1. It is VERY fast and articulate. As a result, it reveals much detail that I never heard before. The HD-600 literally sound like a different headphone. Due to the increased signal quality the amp produces, the HD-600s have slightly deeper bass which is MUCH tighter, a much more neutral lower midrange without any of the nasal bloom that occured with other amps, a really extended high end, and pure effortlessness. The headphones sound like they are breathing a sigh of relief instead of sounding strained. All traces of harshness are completely gone.
To sum it up, WOW. The more I listen to recordings through my player and this amp, the more details I pick up that were just not present prior to this date. Voices that I never even noticed come out cleanly and clearly. Articulation and intonation is pure and effortless.
2. It has EXCELLENT imaging, if a good recording is played, its imaging is much tighter than the airhead, a musical voice such as a guitar or drum or cymbal is like a pinpoint on the soundstage. I am not used to this. Other equipment that I have heard sounds smeared, blurry, or lacks decent imaging altogether (my PDCP for example). In contrast, with a good analog recording imaging is really great and realistic. It's really sharp and so on and so forth.
3. Realistic, neutral soundstage and air. The amp really focuses the soundstage, and this can be good or bad depending on the recording. With bad recordings, I hear just how overproduced a recording is becuase the amp points out just where reverb is coming from. Good recordings simply sound more realistic with a sense of spaciousness through my HD-600s that beats out a lot of speaker setups I have heard.
The first few seconds that I heard this amp, I was wondering what happened to the soundstage on one of my versions of the Bruch concerto. I finally realized that it was presented over and slightly around the symphony, as opposed to being smeared all over the place as with my other equipment (airhead, pdcp). This is just plain cool: My new amp does classical recordings with a much greater degree of realism.
4. A very convincing crossfeed processor. It uses the same design principles as all of headroom's filters, but does a significantly better job than the one on my airhead. On the airhead I noticed a slight difference between the filter being off and on. On the MOH it's totally obvious. The processor attempts to coherently place audio images in a realistic soundstage. It works for everything and makes stuff more listenable. I do hear a slight increase in bass, but that's due to bass focus: Without the processor, I can't tell where the bass guitar or double basses are. With it on, it becomes much more focused.
5. Good flexibility and overall design. This is the least important of all qualities of an amp imho, because for me sound quality and realism comes first. However, it is very worthy of mention here. The MOH is a versatile, well-built amp with some very useful features. A three-step gain switch is provided, as well as the brightness filter and of course the crossfeed switch.
Toggling the gain from low to medium to high results in a doubling of relative volume for each step up.
I did almost all of my listening on low gain with the volume knob between 9 o 'clock and 3 o' clock.
I experimented with gain, though. On Santana's "Supernatural," I listened at medium gain at about 10 o'clock.
The variability of volume levels allows the listener a great amount of headroom. The same recording can be listened to at a whisper or blaring so loud that permanent hearing damage would result quickly.
The stepped attenuator is included in my version of the MOH. I think it is a definite improvement in sound in that when the knob is turned near zero there is absolutely no channel imbalance, whereas with my other amp I had almost total channel imbalance at lower volume levels.
Brightness is a neato feature, and I will experiment with it later on to try and create the ultimate gaming setting for my amplifier (pinpoint location of whispers and footsteps regardless of fatigue). However, I think that I like the sound best with brightness in the OFF position. Sounds most realistic to me.
I would like to wrap this review up by saying that I am satisfied with my purchase and deem this audio product definitely worth the money. However, I think that it's only suitable for driving extremely good headphones or it's not being used to its fullest potential. My DT770s sounded much better but the HD600s were the clear winner.
Also, I am clearly aware of the fact that my $140 budget CDP is not an acceptable compliment for the MOH. I omitted various sonic flaws and artifacts which were a result of the NS500V on redbook mode, because these flaws disappeared almost entirely when listening to SACD.
This amp is a great value for the money and attempts to maximize sound quality. A great buy.
[edit] I didn't make it so brief. Oh, well.
Cheers,
Geek
