Purifi Class D: Junk?

I had a pair of Nord Hypex NC500 monoblocks a couple years ago and was kind of disappointed with the sound  quality. These amps came with input buffer boards that supported the Sparkos and Sonic Imagery discrete op amps, and I tried them both. I preferred the warmer, smoother sound of the Sparkos in the system I had then, but not by much. The Sonic Imagery opamps offered noticeably more detail, but were more sterile sounding.

These amps replaced a Krell FPB-300 which had died for the second time and I decided it was time to sell it for parts (which I now kind of regret), and they really weren't a good substitute. Granted they cost WAY less and were a lot easier to deal with (both weight and power consumption) but they didn't work for me. 

I ended up selling them and replacing them with a Parasound JC-5 which I was much happier with. That was close to 2 years ago. I have since completely changed my system (although I still have the JC5) and have really gotten into DIY. After building a pair of FirstWatt F5 turbo monoblocks and a pair of Neurochrome chip-amp monoblocks, I decided to give class D another try. 

I recently completed a pair of Purifi-based monoblocks. But instead of using the typical Hypex SMPS, I built them with a large linear power supply, similar to what you'd expect to find in a high-end class AB amp (1500VA shielded transformer with ~200,000uF of Nichicon filter caps). As a first round, I decided to use the Neurochrome input buffers which are a well-engineered op-amp design.

I plan to experiment with other designs including discrete op-amps and fully discrete in the future, but with this relatively simple and cost effective buffer, these amps sound quite nice. I'm sure there is some "pride of my own build" bias  influencing my perspective, but I have to say that I was not that impressed with my FirstWatt F5 Turbo build. The Purifi amps are better in just about every way (more dynamic, much more detail, quieter background, sweeter midrange, better soundstage, WAY less heat). 

You can see a couple of photos on my system page. https://systems.audiogon.com/systems/8726

I'm thinking about trying an input buffer using the Weiss OP2-BP op amps next. I've heard good things about them, and it would be interested to compare them to a high quality conventional op-amp implementation. 

@jaytor -- You have a wonderful touch with the DIY projects. If I had the skill and patience to make things so neat and beautifully laid out, I’d be a DIYer myself.

As someone interested in those PuriFi modules, I’ll be very interested in how you like the Weiss op amps. Please do post and let us know.

I believe the Weiss are not plug-compatible with the Sparkos and Sonic Imagery units. Is that right?

Thanks Mike. I believe the Weiss opamp is pin compatible with the Pro series opamps from Sparkos and Sonic Imagery, but not their dual discrete opamps. 
I want to give my amps a couple more weeks of burnin before I decide how to proceed with the Weiss opamps. 

What an entertaining thread. A bunch of people (mainly) with obviously from this thread and others weak engineering skills (at best) with odd exception pumping their chests and egos while arguing about things they poorly understand while making wild and patently false claims about all kinds of things.

w.r.t. the purifi and hypex modules they need an input buffer to operate to specification. They cannot just be driven with a "lowish" impedance source.  They are meant to be driven with a very low impedance source, i.e. like the buffer circuit on the eval boards.  It sounds like the ops supplier is not qualified at what they are supplying.

VTV supplies the amps with various input buffers.....all of which drive the Purifi module with super low impedance. However, they all sound different.  Yesterday, I A/Bed the Weiss op amps versus my custom modified Sparko Labs 2590 op amps......different but in the same league.  Stock, the Sparko is not in the same league at all as the Weiss.  Everything you do makes a difference.  A complex game this is.