I had the chance to listen to the Abyss and Viva Egoista combination a couple of weeks ago. Being a WA234 owner and hearing the Viva may be rather close competition for it I was very keen to finally have a chance to listen and went in expecting great things. I can now sleep soundly with my choice of the 234's now though, I must admit while as a whole the Viva did sound good, it was no where near the level I had become accustomed to with the right tubes in the 234's. Don't get me wrong, the Viva did sound nice but compared to the 234's it was lacking in a number of key areas.
Firstly was the transparency and texture of the music, the Egoista while having plenty of power sounded far too heavy handed and overpowering of the music. It lacked the finer details that the 234's could convey, the Egoista seemed to put its own veil on the music causing the tracks to start sounding overly similar. The sound had plenty of midrange and warmth, but it was over accentuated to the point of feeling bloated and smeared. Another thing that struck me was that the Viva, while certainly powerful, didn't have the same impact and speed that the 234's had. While the speed and impact is comparable between the Egoista and the 234's using the Cathode Output, when you switch the 234's to Plate Output the impact, speed and sheer energy of the sound takes a massive leap ahead of the Cathode and Egoista. Using the plate output can make the HEK almost as impactful as the Abyss when using the cathode output. Which is no small feat, while I prefer the transparency of the HEK the Abyss is indisputably the most impactful and energetic headphone out there.
Compared to other amplifiers I've heard; Cavalli LAu, Cyper Labs Prautes, Luxman P-700u, Schiit Ragnarok or owned WA5, Headamp GS-X MKII. The Viva Egoista does sound better overall. But when compared to the 234's with stock tubes they're about on par, the 234 being more refined, the Egoista being more powerful. But roll in some good tubes to the 234's; EML 45's or 2A3's, some Elrog's or Takatsuki 300b's and some Takatsuki 274b's or Mullard Metal Base GZ34's, and the 234's are in another league.
Another gripe I had with the Egoista is the heat that it runs at, now I expect tubes to run hot, but on the Egoista even the volume knob and rear terminals heat up to uncomfortable levels. When I had a listen the Egoista had been on for a couple of hours, while the volume knob wasn't painful to hold and use, it did get to the point where it would case a little discomfort when held onto for more than a couple seconds. Kind of like getting into a car that's been parked in the sun for a couple hours and grabbing the gear stick. It's not so hot as to burn you or stop you from changing gears. But it's not pleasant, you certainly wouldn't want to rest your hand there.
Also on a tangent I got to hear the Abyss using the new JPS Labs Super Conductor cable, it was an improvement over the stock cable. Though for my personal tastes I still do prefer the Spore4 cables with the Abyss from when I heard the pairing last. The ones I currently have are terminated to suit the HEK but I wish I had brought in my Abyss adaptors and Spore4 cable to do a proper side by side.