Brainstorming Purifi 1et400a amps

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#62
Studley said:
I’m very interested in using Tom’s stellar buffer with the Purifi modules. They can also be configured for gain so perfect for boosting the overall gain of the amp.
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Same here. They deserve an excellent power supply though. Either SALAS SSL v1.3 UltraBiB or the DIYINHK 0.56uV ultra-low noise regulator (it is marketed at "DACs" but it can output more than 1A, and the neurochrome buffer at clipping draws 100mA). Or perhaps an AC-DC converter, another DC-DC and then a CLC filter and a integrated regulator?

Roberto
 
#74
by ergo

Purifi class-D amplifiers - Page 2

Optimized and clarified

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Look at the power inlet -> it seems with RF/EMI filter.


Purifi class-D amplifiers - Page 3

As a comparison base I have a B&O ICEpower 200ASC based power amp and two NCore NC500MP based monoblocks (NC500MP are the NCores with power supply and buffer integrated onto module - not the NC500OEM that would be a direct competitor)

Source has bee the Cambridge Audio Azur 851D and speakers the Wavecor Ardents EE edition

The first impression was that the Purifi sounded better in mids and highs. Even bit more clarity and precision in upper end. But at the same time the subjective feel was that the body of voices and music instruments seemed a bit thin. Like a speaker with baffle step compensation not quite there yet.

We listened with my friend and tried it also by bypassing the buffer and having 851D directly drive the Purifi. That had clear signs of trouble and the thinness remained while some more graininess emerged. Plus there is not enough gain in system anymore to play loud enough with some songs...
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Purifi class-D amplifiers - Page 3

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#76
The Veros One is LKV Research’s top-of-the-line phono preamp.

SIGNAL HANDLING CIRCUITRY:

* LKV Class A: Input, voltage gain and driver functions are performed by LKV’s signature Class A line level circuits, which use no loop feedback. They are constructed using tightly matched jfets and other premium components, including low tolerance metal film resistors and polypropylene capacitors. High accuracy (effectively zero distortion at musically most important power levels) is achieved using current source biasing, cascode amplifier topologies and differential (balanced) amplification.

* Purifi Class D: The Purifi module embodies Bruno Putzeys latest (Patent Pending) advance in amplifier control circuitry. This innovation for the first time enables very high feedback to be maintained throughout the audio spectrum. As a result, the high frequency problems that have plagued all previous feedback amplifiers are banished. The complete audio spectrum can now be delivered to the speaker without degradation.

POWER SUPPLY:

* Linear Power Supply: Specially designed (1) to enhance performance of the Class A and D circuitry, and (2) to avoid sonic issues that can be caused by switching supplies.

* Transformers: Three separate toroidal power transformers are employed in the PWR+: (a) One large 1KV transformer weighing over 12 pounds supplies high current for the Class D output stage. (b) A second serves as a floating, +15 volt supply for the driver circuitry in the Purifi module. (c) A third feeds the power supply for the LKV Class A input/gain/driver stages.

* High Current Supply: This power supply employs almost 40KuF of capacitance and is specifically designed to meet the demands imposed by Class D amplification circuits. Most importantly, it copes quite effectively with “power pumping,” a problem unique to Class D amps.

* Line Level Supply: To assure the very accurate, low noise/distortion performance for which the LKV Class A circuits are known, each power rail in this supply has two stages of power regulation, a capacitance multiplier, and 40KuF of capacitance.
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#80
So NAD has fired the last amp developer and replaced him by a bunch of marketing nonsense writers. Any generation gets the products they deserve.
MP3, i-phone, Alexa and company have preconditioned the ears of future buyers, so some cheap amp module, available to any DIYS idiot, is the future measure of superior sound quality.
What else could we expect from a generation that virtually lives inside of their smart phones and prefers Facebook, Instagram, Twitter, Snapchat, Pinterest, Tumblr and reddit to seeing reality with their own eyes?
It had to come. S*hit in = S*hit out.

PS: NAD uses Gorilla glas on their products now. They know what apes need!
 
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