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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
millercarbon's avatar
millercarbon
12,531 posts
 
I am sure that changing a part here and there could change a measurement. However, this us not the usual case.

What is it with people feeling its okay to pontificate and lecture about things they clearly haven't the foggiest about? To an audience chock full of people who do?  

Ralph has more experience in his little finger but even I have enough to know its darn near the OPPOSITE of what this ricevs guy is saying. First swap I ever did was a diode, just a dumb little $8 hexfred, and the improvement was massive! Changed caps- huge. Fuse- ditto. On and on.  

Actually did these things. Actually heard these differences. Just a suggestion ricevs, but I really do think what you should do for at least a while, every time you're all set to start blathering about that which you have no actual experience or knowledge of, type the words, "Of course I have no clue if this is right or not because I haven't done anything even close to this before but...." and then type away. 

Deal?
georgehifi's avatar
georgehifi
10,312 posts
 

ricevs
Almost all tube manufacturers....they pick caps, etc. by ear....and they don't measure any different.
atmasphere This statement is false- they do indeed measure differently (whether some companies bother to measure the differences is a different matter). We use custom made resistors as well (made by Caddock); they sound better but they also measure better.
I couldn't agree more (wow that's one for the books)
Any manufacturer/designer or modder worth his salt, will use all the EE laws at hand to design, then build/measure/bench-test and listen. And if they don't like it, they change things using all the EE laws/measure/bench-test again and listen once again till they get it right. Any fool that say otherwise is a hoax and a snake oiler.

Cheers George  

ricevs
1,543 posts
 
Miller,
I do not understand what you are saying to me. I am the one saying everything makes a difference and I have been doing listening tests for over 40 years. I do know what I am saying because I EXPERIENCED it, just like you did. Maybe you are confusing me with someone else. I am confused by your comments above......maybe you are confused. Check out my website...you will see how crazy I am..... he he.

BTW, what you quoted from me is true. I am not talking about changing a transistor or tube or making a circuit change. I am talking about changing a brand of solder, wire, resistor, cap, etc. to a different brand and measuring a difference. For the most part, you cannot measure the difference between different brands of solder/parts.....that is the truth. measurement wise.
atmasphere's avatar
atmasphere
11,834 posts
 
Can you illuminate me on what types of differences, among equally rated and types of fuses you have encountered? How precise did the DVM have to be for you to measure it, and what qualities do you look for?
The voltage drop across the fuse varies. The better sounding fuses correspond with the least voltage drop ('better sounding' doesn't always correlate to 'boutique', just to be clear). I use a Fluke DVM that's 3 1/2 digits. Like I said, its not rocket science. I prefer to use Littlefuse or Bussman. 
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