My HUGO and M8 and modi all sound different...
Let me have my test review here
Here is how I get my impressions and why I think it makes sense:
I have 3 DAC(HUGO, M8, MODI) at once for about 6 months, avg listening for 2 hours per day. There was one week in may when I switched between the 3 DAC, tested them and then listed one for sell, one gave away as gift, one for myself. I tested them with the same source(gaming notebook), input usb cables with jitter bug usb cleaner, output RCA cable, wall power, headphone AMP(jotunheim high gain single end) and headphone(HE500) and the same software setting(JRiver exclusive mode) and music files Beethoven Symphonies 5 & 7 - Honeck, Pittsburgh SO (Reference FR-718).
The 3 different DAC sound like 3 different DAC. The modi has the most to-your-face soundstage while all instruments are tied together and the rear instruments(basses, horns and trombones etc...) don't sound like on the back, but only sound like being covered by the front due to lack of details and their harmonic overtone got overwhelmed by high frequencies noise from pc. Modi also makes everything sounds much brighter than live perform. M8 has a more realistic brightness. The rear instruments don't get overwhelmed by the front too much while airy details from the front are still there. Its overall a more 3D, not overly bright sounding DAC. Therefore if the instruments are brighter than they should but instruments are still not well separated, then I must be listening to a MODI not a M8. Because their harmonic overtone sound like being overwhelmed by the brightness of all the fundamental sound of the instruments. When the high frequencies details and harmonic got messed up, the soundstage got messed up too. The Hugo is a larger jump again. Each instrument sounds more like what the sound in real life. The fundamental sound of the instruments are more detailed and weighted, without disturbing restless noise from PC which makes everything sounds too bright and out of place. Therefore the harmonic overtone is all there, its warm and airy and all instruments own a body on the stage. Maybe thanks to the well written Xmos interface and clean battery power or something in the HUGO, the shiiit PC noise do not get in my music as much as the 2 other dac while having good detailed sounding chip and stuff. Hugo simply tastes better.
I have to say all 3 DAC I have are not for symphonies because they all have the to-your-face soundstage compares to full size pro DAC. However they are still different enough for me to tell which is which. Back to the volume matching issue, if the violins sound too bright, no matter how you turn the volume up and down. You wont make it natural wood sounding again. If the orchestra instruments are well separated, there won't be much noise to jam the airy details no matter how you turn the volume up and down.
One of the most important factor in my test which makes my 3 DAC sound so different is definitely not the volume, but my very poor source(gaming notebook). I can't believe none of you point it out yet. Its has tones of jamming noise passses to the DAC. Since my modi is USB powered, it only amplifies the weakness of the DAC and make the already not very revealing chip even worse. I do believe the DAC is not what makes the music really bad but the tech failed to handle the noisy power is. I actually used a high end 204 interface between the PC and DAC. That proved what I thought. PC + int204 + linear power supply +modi uber sounds much much better than PC + Hugo/M8/modi/modi uber. However the int204 costs more than the rest of the system.