I've had my Euterpe for a month. I use it primarily with a Meze Empyrean headphone and Chord Qutest DAC. For anyone who has a Meze Empyrean, this amp is highly recommended, as they are a great-sounding match, if you replace the supplied ECC81 tube with a JJ Electronic gold pin ECC82, which provides a more neutral and extended frequency response. With the stock tubes, the highs were a bit rolled-off, and in that case, the amp sounded best with my Focal Radiance. I also tried replacing the supplied Ei PL95 tubes, with a pair of G.E. EL95, and a pair of Mullard PL95. However, none of these replacement tubes sounded as good as the original PL95 tubes supplied with the amp.
This product is described as a headphone amplifier, DAC, and Pre-amp. However, for me it fails at the latter two functions. The DAC is poor quality. Anyone who already has a DAC is probably going to get better sound using the DAC they have. I tried 3 different DACs that I have, and the Euterpe sounded better with any one of them, compared to the internal DAC. Ultimately I just disconnected the USB cable.
The quality of sound from the pre out is so poor that I will not use it. I connected my KEF LS50 powered speakers to the Euterpe pre outs. With the Euterpe’s impedance switch on L, there was a constant high-pitched hum from the speakers. Switching impedance to H eliminated the hum, but the quality of sound was too poor to use. I have used many headphone amps, but never before heard such bad sound from their pre outs.
Operating the impedance switch sometimes creates a static sound or momentary dropouts in the left channel.
One other minor issue: As shipped to me, the EL95/PL95 switch was in the wrong position. Fortunately I noticed and corrected this before powering on the unit.
In summary, I had significant complaints about the internal DAC and pre-amp outputs, but I love the great sound I get with my favorite headphone, the Empyrean, and I enjoy using the Euterpe every day.