DAC1 was extremely clean, but a little thin sounding in the lower midrange. Replacing op-amps made sound a little more vivid and fuller, but DAC3 is much better overall. Sound is still very clean and extended on both ends, but midrange sounds much better - cello sounds more natural, male voices have more "chestiness". Background is darker, sound more refined.
I jumped from DAC1 to DAC3, so I cannot comment on the sound of DAC2. I use DAC3 with AHB2 amp with great results.
I’d like to mention another difference between DAC1 and DAC3 HGC (Hybrid Gain Control) - volume control. DAC1 volume control got static noise over time. I was able to slightly bend the back of the pot and force in "Fade lube" spray (Deoxit). It worked fine for few years after that, but started to exhibit the same problem again. DAC3 HGC, having digital volume control for digital sources, is free from this problem without any negative effects (at least I don’t hear any).
I jumped from DAC1 to DAC3, so I cannot comment on the sound of DAC2. I use DAC3 with AHB2 amp with great results.
I’d like to mention another difference between DAC1 and DAC3 HGC (Hybrid Gain Control) - volume control. DAC1 volume control got static noise over time. I was able to slightly bend the back of the pot and force in "Fade lube" spray (Deoxit). It worked fine for few years after that, but started to exhibit the same problem again. DAC3 HGC, having digital volume control for digital sources, is free from this problem without any negative effects (at least I don’t hear any).