I just received this in the mail and had a chance to compare it last night to a Gilmore Lite MK2 and a Violectric V280. My initial impressions, feeding it with the Modi Mutibit and using the Focal Clear and MrSpeakers Aeon Closed are as follows, keeping in mind that this is not a full review, which @TORQ is much more capable of delivering.
So, without getting into a full blown review and comparison, I will just say that all three amps are technically very proficient and deliver what is expected of a competent amp, but sound differently, with the Gilmore sounding the closest to the 789, which is the least expensive of the three and as such, probably the best value. The 789 sells for $350, the Gilmore for $500, and the Violectric $1800.
Again, without getting into a detailed comparison, my immediate impression after a quick A/B/C is that compared to the other two amps, I find the Massdrop THX AAA 789 to be rather polite sounding in that it lacks slam and authority, especially when listening to very dynamic tracks like Florence and the Machine’s, Dog Days Are Over or Max Richter’s interpretation of Vivaldi’s The Four Seasons, Summer 3. Although I had level matched the volume of all three amps, with the 789 I always wanted to turn the volume up in order to feel the excitement those pieces convey but it never quite got me there. I should also add, that in comparison, the 789 is somewhat lean sounding and gives the impression of having a tad amount of brittleness or sharper edge on the higher notes and as such, while being polite sounding, can probably get fatiguing compared to the other amps. Although, perhaps it is the thinness of the notes that makes them seem a tad brittle. I am not sure. I should stress here however, that this is only in comparison to the other 2 amps, which others have said exhibit “tube like” characteristics. But I don’t want to go there.
While the 789 is less expensive, I prefer the Gilmore as it is not only more exciting to listen to but more fulfilling, in that it is more full sounding with thicker, rounder notes but it is just as fast, just as detailed and with a stage that is similar in size. The 789 is perhaps a bit more nimble sounding or lighter on its feet but at the expense of weight and punch.
Of the three, I think I prefer the Violectric because while it has more authority, weight and slam than the other two, it also has a creamy quality to it, and while this gives the impression of slowing things down, in the long run it is less fatiguing to listen to. The notes have more body and weight than the other two amps. They are also rounder which makes female vocals sound luscious. And it does this while maintaining a semblance of air and separation between the notes. Ideally, I would prefer a hybrid of the Gilmore and Violectric - the speed and excitement of the Gilmore mixed with the creamy, round and powerful sound of the Violectric.
If I did not have the other amps to compare to, for $350 the Massdrop THX AAA 789 would be a keeper and is I think a fantastic entry level amp but for a bit more money, I prefer the Gilmore Lite MK2.