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
bluemoodriver
193 posts
 
Doh! <slaps forehead>
kawzx7
5 posts
 

Hello, does anyone know the current engineering revision level of the Purifi class (J)unk Amplifiers? Putz apparently says Class A could do with some improvements, but Class (J)unk cannot stand on its own merits. Someone said that there were amplifiers that were over $20000 with these modules inside them? Talk about a ripoff. The % profit margin must be in the 4 digits.

atmasphere's avatar
atmasphere
12,061 posts
 

@kawzx7 

Any Purifi module isn't junk! - they are all excellent. 

The problem was the mix and match approach that spawned this old thread had the expected result. If you want a class D amp to sound good, you have to give it a respectable power supply like you would with any other amplifier. If that happens to be a switch mode supply, to really make it work it should be designed for the application rather than something off the shelf, even if that off the shelf source is excellent.

The input buffer can have a big effect too. Its a sad state of affairs that so many class D amps get shot down on this account.

Any bugs in either of these departments and the whole thing goes down the loo.

If these issues are properly controlled you find that a class D amp can be just as good as the best class A amps price no object.

erik_squires
16,554 posts
 

Thread from 2020

More to discover