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Purifi Class D: Junk?

So, from the previous thread about high-end class D the Purifi module was brought up. I decided to get a cheap example from VTV, a simple stereo unit with a single Purifi module and matching Hypex SMPS. Standard input buffer. I got it in yesterday. First impression wasn't what I was expecting: weak, congested dynamics is what stood out to me. I expected greater expression through my ProAc D30Rs. The other problems such as poor soundstage, thin / boring character, etc, I marked up to needing burn-in before evaluating. So it's been 24 hours, I would still expect to get at least the high control / damping of high end class D and dynamic power, but it's just not present.

Could it be an impedance mismatch? Other manufacturers selling the Purifi with their custom input buffers are reporting 47k Ohms. VTV doesn't say in the manual or on the site. I checked the Purifi data sheet which reports...2.2k Ohms on SE???? That can't be right?? That's absurdly low! Am I reading the right spec? My preamp has an output impedance of 230 Ohms. Can someone confirm that the stock Purifi has this ultra-low input impedance?
madavid0
georgehifi's avatar
georgehifi
10,312 posts
 
If the defeault Hypex board is really that compromised
I’ve got those those Hypex buffer boards in my NC500 mono’s that have my own big linear supplies, there’s nothing wrong with the buffers (they don’t sound bad as some here would like you to believe) Your problem is elsewhere.

Saying that, my MSB discrete R2R dac has got volume control in the digital domain with up to 5v out balanced, and by-passing the Hypex buffers altogether and going direct from the MSB's balanced output into the balanced input of the NC500 modules, the sound took on a massive improvement in transparency/dynamics and slam.

(Moral of the story: Less is more, just like I always say with passive pre’s vs active pre’s also when possible)

Cheers George
ricevs
1,543 posts
 
"I don't get why Purifi thought this thing sounded good enough to release to the public"  What are you talking about?  You are not hearing a Purifi.....you are hearing a Purifi with a Hypex buffer put together by VTV.....The Purifi can use any buffer on its input.........a stock Hypex buffer board, a Purifi buffer board....a VTV buffer board with various different sounding discrete op amps....and then are mods to the input boards, mods to the input stages, mods to the Power supply, AC inlets, etc. etc......You really don' t seem to have any idea of what you are talking about.   
georgehifi's avatar
georgehifi
10,312 posts
 
a stock Hypex buffer board
There is nothing wrong with that buffer, Putzy's not an idiot to release a Hypex product that kind of bad sound ****
ricevs
1,543 posts
 
You say there is nothing wrong with it and at the same time you say there is a "massive improvement"  when you bypass it.  You cannot have it both ways.  Every op amp....every regulator......every everything....has a sound.  So all buffers, etc will sound different.  Some will sound bad, some are OK, some are good, some are really good, some are great.  If you bypass it and you get a massive improvement.....then certainly, it is not great.
georgehifi's avatar
georgehifi
10,312 posts
 



Wake up!! Did you come down with the last shower?

It doesn’t sound ****, like your making out.
And of course, leave out any buffer regardless of how good if one can with high output source, and you’ll reap those benefits of extra transparency/dynamics and slam, by going direct into the Class-D module with no buffer at all in the way.

And that Hypex buffer is a perfect match with the Purifi module, that’s why it’s called and marketed as a buffer.

It something else the OP is hearing, and you know what that leaves, the Purifi module itself!
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