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  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
oldhvymec
5,101 posts
 
The one thing I did dig out of the thread is, I need to pick up a pair of Nord built Purifi 1ET400A, with Nord buffers and Sparco 2590. He'll give me a deal.

I own 9 of his NC500. I bought 5 from him. 3 pairs of MBs and one X3 NC500 with trigger and 3 x PS (no sharing). ALL use 1200/700 PS. All but 2 have rev. d boards (rev c). Let's say we have a rapport. 
My 3X was the first to roll off the line with rev d boards and multi Mono rail within a single enclosures, withOUT shared (or compromised) PS 1200/700. Serious piece of gear..

Now to modify the fuse circuit. It needs to be inline and remove the onboard 15 and add a 20 amp iec copper/silver non fuse female.

These are great sounding units with small planars MUCH better than any of the earlier 400/500/700. I really didn't like that sound as ALL.

The buffer made all the difference in the world for me.. BUT then I like tone control, Mcintosh and VMPS speakers. I'm one of "those guys".

To top it all off, kenjit, kicked me off his forum, I'm heart broken.. (took a while to work). Ok I all better now.. I'll quit yipin', I mean typing. :-)

Regards
Post removed 
ricevs
1,543 posts
 
The Nord board is not better made and the VTV board has the exact same options as the Nord and VTV sells more op amp options. You can use any of the the op amps that Nord sells and more. There are no copper foil resistors on the VTV board......what the heck is a "copper foil resistor"? He uses standard metal film resistors that were tested by Andrew Sparks as having the lowest noise.
ricevs
1,543 posts
 
Here is a comment from someone who bought the VTV buffer boards and installed them in his NC500 amp.....this is from the VTV website:

"I purchased a pair of the VTV input buffer boards for my NC500
amps using the Sparkos SS2590 opamps and WOW.
I must add that I have been using the Nord RevD buffers and before that the Bellissimo Audio buffers. I had tried the SS3602 and preferred the SS2590 in each case. After installing the VTV buffers in low output configuration I was blown away. The amp was more cohesive with smoother overall performance and finer details also better bass."
oldhvymec
5,101 posts
 
Ok I looked at my Nords and my phone pics. I deleted the pic of the boards after I returned them..

Now I remember the whole deal. I bought 2 buffer boards and 2 Wiess opamps. They arrived but it took 4 opamps to do 2 boards. It was worded weird. I looked the boards over, and he (whoever built the boards), didn't use copper foil resistors and the work on the boards was not as nice. Plane and simple. 

I didn't get to listen to the Weiss, as I recall. I was ticked that I need two more. 950.00 for a pair.. 700.00 for the Nords..

The boards side by side, LOL yea, about that... VW vs Porsche.
The boards I looked over..
Even Rev C had copper foil resistors vs Weiss with cheapos.

They can take the 2590s I was mistaken, I was ticked the it took 4 Wiess Op Amps and he sent me 1/2 what I needed. Didn't make any sense.

The guy couldn't read my mind.. Go figure.. My mistake..:-)

They were sent back. Customer service was great though.. No problems at all.. Good guy to deal with..

I'll stick with Nord.. only problem it's in England.. Turns out it's not an issue so far, 5 years now with class ds Hypex NC500, no issues..
Sure like them better than the ICE products.. I have Wyred4sound, too mercy.. Where is the tone control..

Regards
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