Re: Using an external headphone amp with the DAVE and Abyss Phi Background When I got the DAVE, I was a bit concerned about its capability to drive my Abyss Phi headphones. At the time, I had the Audio GD NOS11 DAC/amp, which has a very powerful amplifier section (about 8W at 50Ohm), so I thought that if I was not satisfied with the DAVE amp I still could use the NOS11. I was very happy when I noticed that the DAVE direct could make the Abyss sing as easily as the NOS11 amp, with much better transparency and speed. I tried some explosive tracks, such as the Tchaikovsky Ouverture 1812 (those cannons!) or the Grieg’s funeral march for Rikard Nordraak (very violent tympani attack at about 1:00 on the Reference Recordings version), and some organ music for the lowest registers, and the DAVE coped well to the much more powerful NOS11 amp in terms of impact and extension, while meeting my usual loudness demands. Based on this, I decided do sell the NOS11 and go straight from DAVE to the Abyss for the next future. That audiophile itch ... I am enjoying the DAVE + Abyss combo very much since several months now, and I could very happily have lived with it as my endgame set-up. But (of course, there was a “but” coming), occasionally I was feeling that I was not getting the very last drop of juice out of my music. I like to listen to classical – actually that’s most of my listening – and other acoustic music to realistic loudness levels (i.e. those I experience at the live event), and, especially when the recording level is low (which happens often on classical recordings to allow headroom for 20-25dB dynamic range) I was a bit let down by some lack of dynamics and a slight flatness of presentation. It was not only a matter of SPL, but also / mostly about the visceral impact of abrupt dynamic changes. Also, bass extension is extremely good with Abyss + DAVE, but the very last octave (40-20Hz) was a tiny bit rolled off in some cases and less physically involving compared to live feeling, while still being the best I heard from a headphone system. Scratching that itch is expensive ... I was not sure this was due to the amp, or to the Abyss or to my hearing sensitivity or tastes, but anyway I decided to try again an external amp with the DAVE, and this time I decided to go with the most synergistic approach I could figure out (and afford) by choosing the Eleven XI Audio Formula S amp + Powerman external power supply, i.e. a combo which was allegedly developed to fully exploit the AB 1266 headphone potential. During my money-back return period, I half hoped that the XI Audio gear did not make a significant difference to save my pennies for something else (non-audio related), but ... well, if you’re a member of the (audiophile) “lunatic fringe” (cit.) you already know how this ended up DAVE direct vs. Formula S + Powerman I started playing high-dynamics classical music, namely the tracks mentioned above, plus some symphonies from Beethoven and Mahler, and a few romantic piano sonatas with challenging dynamics transients. Not only both visceral impact of extreme dynamics transient and sub-bass response improved, but the overall sound presentation acquired more breadth, spaciousness and soundstage size. While no specific coloration has been added, the whole musical spectrum appears slightly warmer / darker and richer of harmonics (especially at medium-to-high volume), musically complex passages played at lifelike levels (think orchestral fortissimos) keep openness, composure, readability and texture, instead of becoming slightly congested / compressed. Organ tracks become literally skull rattling, and I can feel the air displacement from the lower frequencies or from sharp transients (double bass attack) coming from the Abyss drivers at full. Switching to more relaxed and quieter genres like baroque or small jazz combos, or acoustic / vocal tracks changes the scenario to a much more mixed feeling. With the Formula S I get this slightly thicker and more open presentation, and the tonality of the woods is a bit sweeter (less strident) and more fleshed out, but the sheer transparency, depth of field and detail retrieval of the direct DAVE drive is unmatched. Room reverberations, ambience effects, minute background noises, very delicate details like the breathing of a singer or even he/she moving or licking his/her lips are better captured by the DAVE and the shivers I get from these cues are just more intense. The pristine transparency you get from DAVE directly is somewhat veiled with the Formula S, but to notice this I had to do repeated A/B tests on specific tracks, and I still would rate the DAVE + Formula S as utterly transparent as a combo. Double bass attack, physical impact and decay, deeply descending scales of electric bass, drums solos are just amazing with the Formula S in the chain. Classic rock (Dire Straits, Pink Floyd, Springsteen, Led Zeppelin, Police, ...) is also more satisfying via the amp thanks to its slightly more forgiving nature, and the additional fleshy tonality and bass oomph, and so are the occasional pop / EDM tracks I tried (U2, Depeche Mode, Daft Punk, ...) especially when played LOUD. So, was adding that amp to the Abyss worth? There is no 2-letter answer to answer to this question, I am afraid. To me, adding an external amp to the DAVE when driving the Abyss Phi, is most certainly not “necessary” and I can see myself coming back to DAVE alone depending on mood, listening volume, music type. That said, for some music genres like large symphonic works, tumultuous piano pieces and generally explosive dynamic compositions / passages, and in certain areas of the spectrum (e.g. the deepest bass frequency) the uplift of my music enjoyment from the Formula S is really significant. Since I am intoxicated by the physical, emotional and intellectual (?) experience my Abyss headphones are able to provide, I have decided to do what I can in order to make them perform at best in every possible musical context, so I am happy to complement the DAVE with the XI Audio gear. Of course, I feel I am well into the diminishing return here, and you may get much better value for (this kind of) money by upgrading other components of your rig - or spending in a nice vacation in Hawaii, or buying CDs or going to live concerts for the next few years, for that matter. Just as a final word of caution, I have found that you may also make the DAVE sound definitely worse by adding an amp, so not any powerful and / or well-reviewed amp is going to be worth, and synergy and subjective taste are key factors, as usual. Sorry for the lengthy post, hope it is helpful for somebody ... also, I would be very interested in others' experience when pairing the DAVE with an external amp to drive demanding HP’s!