I decided to register here to discuss the Purifi modules. I recently purchased a stock Purifi stereo amp from VTV. It was noticeably better than every other class-D I've heard before. However it suffered from a really bad mid-range: blurry and artificial-sounding. Just awful. I almost returned it, but I was talked into buying a pair of VTV custom input boards with Sparkos opamps. The upgrade is on the way and I'll update the thread with my findings. A few other peculiarities:
- Burn-in time. It seemed like it needed more than the usual amount of 200 hours, maybe closer to 300 hours. I wasn't counting. But burn-in was essential, out of the box the amp was atrocious: narrow soundstage, no dynamics, lacking in bass control (something I expected it to be good at out of the gate). Unnatural sounding.
- Doesn't care about mains quality. I tested my reference amp mains: Lessloss Level 1 filtering cable + Lessloss Firewall 64X into a Furutech GTX-D(r) NCF outlet against a bog standard black (14ga I believe) mains cable into a regular outlet in my listening room. I could not reliably tell the difference between them. Perhaps there was a minor difference but the change is so small it wouldn't overcome audio memory effects. In fact, I think all the class Ds I've tried have had this issue. Perhaps something to do with switching mode power supplies?
- The Purifi seems to have been engineered to bring back even-order harmonics -- or at least that what it sounds like to me. The sense I get that in terms of harmonic overtones it's truer to life than what I've experience in all other class Ds. I disagree with the assessment that it's "clinical" or "dry". However this could be because of my all-tube preamp, a Yaqin B-T2 with all NOS and Herbie damping rings. I just got cheap-o NOS tubes as I didn't want to spend big $ on high end NOS if I didn't want to keep it long-term.
- Lack of engagement. Compared to my current reference, an Odyssey Kismet, the Purifi is seriously un-engaging. However this may be completely the fault of the compromised input stage. Possibly the ugly midrange is what is killing it for me.