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
clearthink
1,421 posts
 
djones51"I assume these various opamps are being compared sighted, I doubt in a blind test anyone could tell one from another."


Perhaps you should test you're theory by actually conducting proper, appropriate, repeatable blind tests but I suggest and recommend that you engage other listeners in the test because I do not think you will hear a difference because of your "expectation bias" that you won't but it would be an interesting exercise for you undertake to determine, establish, and substantiate you're claam.
djones51
4,947 posts
 
My theory has already been tested, none could tell a difference. Better luck next time.
t_ramey
632 posts
 
@djones51 

How did you guys do the blind test with the VTV amps? Did you have one Purifi amp with 4 or 5 opamps to switch out or did you have 4 or 5 Purifi amps with a different opamp?
clearthink
1,421 posts
 

djones51"My theory has already been tested, none could tell a difference. Better luck next time."


My English suffices for me to detect this an an insult, which is the type of response we could expect from someone who makes a broad, sweeping, over "arching" claim for which he has no proof, substantiation or references and which reflects an underlying inability to comprehend or understand the actual topic under discussion so as you say "Better luck next time" if you want to be accepted as an authority or expert.
djones51
4,947 posts
 
I never said I tested the theory. I see no reason to educate anyone on sighted bias. The only way anything claimed about opamp sonic differences is if they were tested in a proper controlled blind setting. Flowery subject anecdotes while highly entertaining gives no valuable information. Thanks for playing. 
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