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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
georgehifi's avatar
georgehifi
10,312 posts
 
Nothing like a tweaked IceEdge or tweaked Purifi.
Save use all, looks like another one bringing out his new "tweaked" Class-D, probably has an orange fuse in it too

Can anyone save us us against boutique Class-D manufacturers using threads to promote their own yet to be released stuff onto the market.

BTW Those $300 3000w Behringers are ICE POWERED modules!!!!

Two problems Class-D have still.
The switching frequency, which is fixable with GaN technology the way only Technics so far have used it.
And the second, is current delivery, where wattage goes up almost doubling for each halving of impedance down to 2ohms or even less.
atmasphere's avatar
atmasphere
11,834 posts
 
Take it up with the likes of D’Agostino, Curl, ect ect manufacturers of the greatest amps that are recognized as being able to drive speakers with loadings that make Class-D’s run for the hills, they will tell you the same thing.
Actually they won't. They will all tell you the same thing- the limit of any solid state amp, class D or no, will be current the output section can withstand, the ability of the heatsinks to adequately cool the devices and how much current is available from the power supply.

I will note one thing though- I've seen a number of SMPSs (Switch Mode Power Supplies) used in class D amps. I think its a bad practice. They work, sort of; the problem is that class D amps go from almost no current draw at idle to quite a lot at full power. SMPSs don't have a lot of capacitance at their output and so can be drained faster than they can replenish. A lot of them will shut down if you put a lot of capacitance at their output. So if you're not running an amp with a regular power transformer and a lot of capacitance available for the class D amp to feed on, you're probably not hearing what it can do.
georgehifi's avatar
georgehifi
10,312 posts
 


Actually they won't. They will all tell you the same thing

Yeah, get them to confirm that big furphy
ricevs
1,543 posts
 
Can anyone save us from Georges constant negativity?

I own one of those Behringer amps.....there is nothing in there that resembles anything made by IcePower.  Even if it is a custom IcePower it is junk.  i don't even like it that much on woofers....and I modded it.
art_boston
45 posts
 
So if you're not running an amp with a regular power transformer and a lot of capacitance available for the class D amp to feed on, you're probably not hearing what it can do.

Exactly true. That's what allows the H2O Audio S250 Signature to run Scintillas with ease and quality, albeit with old B&O modules. I'll take this old school approach with current class D anytime!
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