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
madavid0 OP
214 posts
 
I'll look around the local dealers to see if they have a SE-R1 for audition.

I really am giving class D a lot of chances. Maybe I really want to believe in the promise of high-quality audio in a small and cheap package. But I didn't go into this with my mind made up, I was successfully talked into trying it by you guys (and others). I really have to question though what are some of you guys' standards in audio. It's still burning in so we'll see. I hope this mid range mess sorts itself out.
soix
8,604 posts
 
Kudos to you @madavid0 for giving Class D a solid shot. Maybe send it to @ricevs to do some magic mods to it and then we can all enjoy watching Georgie sunshine blow a circuit.
ricevs
1,443 posts
 
You buy the bottom of the line VTV amp and you think you will know anything about class D or Purifi?  This amp is $979 delivered including shipping.  It uses a one dollar op amp for the input buffer (LM4562) and two one dollar 3 pin regulators.....here is the part listed on Hypex site:

https://www.hypex.nl/product/nc500-evaluation-board/51

This is NOT going to give very good sound.  The input board from Purifi is better....at least it uses 1612 op amps and a discrete regulator.  However, the input board that VTV makes that uses discrete op amps and discrete regulators is much better sounding than the Purifi board.  In fact, I will not mod any VTV amp that uses the stock Hypex input board.  This is not serious....this is for people who want to spend as little as possible.  The discrete input board will take the amp up another level....but my mods take the amp to many more levels up.  You are just playing around with that VTV.  I will have an eval amp out for tour....so you guys can really hear what class D and Purifi can do.  A fully modded stereo VTV Purifi amp using modded Sparko labs op amps is around $2600.........not cheap....but a lot less than a $10K LKV. 
georgehifi's avatar
georgehifi
10,312 posts
 
Maybe send it to @ricevs to do some magic mods to it
Don’t know about mods without any tests/measurements/to back up any subjective listening claims. But "voodoo" and "snake oil" maybe.

As for the LM4562 it one of the better opamps around, it’s even used in some discrete MSB dacs and many others.
And as for your OPA1612 is no better and cost around the same. Just more "snake oil" talk from Tweakaudio, EVS or whatever you call your self these days

ricevs
1,443 posts
 
It is best just to ignore George. He goes on and on saying the same nonsense about stuff he has never listened to. Let him have the last word or it will go on forever......go on George, you know you have to.

Maybe we should use a new word for people like this. How about Anti Snake Oiler or ASO. Much better than "fuser" (word made up by George to vilify fuse lovers). If you look closely you will see the humor.....he he. I love you George. You are so entertaining.
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