2. amps-preamps
  3. 162284-76532

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
audio2design
1,351 posts
 
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.
ricevs
1,543 posts
 
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.
ctbarker32
8 posts
 
My videos about VTV have been popular. Also check out my Roon - 10 things you don't know video.

VTV Purifi Amplifier - Input Buffer Upgrade Video
https://youtu.be/Jj1jJPuda8A
ricevs
1,543 posts
 
Chris,
Have to formed an opinion about the sound of the vtv amp with the baby sparko op amp versus the Hypex board and have you listened to other discrete op amps and compared sonically with the baby sparko?  I think a lot of people would like to know what all these options do to the sonics.  Do we get more by paying more?
djones51
4,947 posts
 
I assume these various opamps are being compared sighted, I doubt in a blind test anyone could tell one from another. 
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