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History. For a mini primer on Bruno Putzeys, after high school he wrote his thesis on class D audio at the National Radio and Film Technical Institute in Brussels where he graduated bachelor in electrical engineering. Dutch electronics giant Philips Applied Technologies of Belgium's Leuven had sponsored his thesis work to now offer him a position. This involved designing class AB amplifiers around core modules from Philips partner Sanyo. Getting bored Bruno eventually had himself reassigned and in charge of testing a class D audio chip which Philips had designed for a television set in another division. Putzeys challenged his bosses that within a month's time he'd have designed something far superior from discrete parts. Three weeks later he really had a 25wpc class D amp with better specs than the IC version which the Philips 4-man team had worked on for two years.
By 2001 the Philips executive George Aerts had secured funding to allow Putzeys R&D time to create a small affordable high-performance class D module which would be suitable for a broad variety of applications. Eight months and four generations later Bruno delivered a compact class D module which he called UcD for Universal class D. Not much happened with it at Philips however. Then Jan-Peter van Amerongen who ran Hypex Electronics to supply amps and other gear to active speaker manufacturers and recording studios visited in 2003. Impressed by the module's performance on a scope, he immediately signed up for the license. By May of 2005 Bruno followed his modules to Hypex Electronics of Groningen/Holland where he's been the resident head designer ever since.
He also is one fourth of the Grimm Audio team of Utrecht/Holland—their active LS1 speakers run on Ncore power—and one of his prior high-end endeavors was designing Kharma's MP150 amplifier with linear power supply above [present NC1200 module at left].
To understand the Ncore development [NC1200 with matching SMPS at right] means a closer look at its specs*. Besides ultra-low distortion including IMD, the perhaps most 'text book' is the output impedance. Measured directly at the terminals, it's 1.3mΩ from 20Hz to 17kHz and only 3mΩ at 20kHz. That's "lower than the resistance of three feet
of 4-gauge speaker cable" and shockingly linear across the audible bandwidth. Noise floor relative to 1W/8Ω is better than minus 130dB. Total unweighted noise is 24uV. "The original UcD circuit has a remarkably simple
comparator circuit consisting of six transistors and
two diodes. The new comparator circuit with ten transistors is a
lot faster and handles much smaller signals. The
match between predicted and actual distortion
performance is now almost exact. This results in low
distortion right until the onset of clipping. A
new driver circuit significantly
reduces idling losses and improves
crossover distortion." Only the HF response still betrays class D limitations by being ruler flat to about 8kHz, then down 0.4dB at 20kHz which is identical behavior into 8, 4 and 2Ω.
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* All measurements were conducted on an unregulated supply despite class D amps being known to be sensitive to AC power supply conditions. Voltage ripple was 2V yet all mains-related artifacts of the amp are at least 135dB down.
Those self-conscious of driving stock Ncore when 'more advanced'—or simply changed, deliberately voiced—iterations could wait behind recognized boutique names like Jeff Rowland & Co. can always stand the same argument on its head. Call it your guarantee against dealing with second-guessed iterations tweaked by folks not bright enough to develop this module in the first place.
Call it your guarantee to hearing this circuit exactly as its creator envisioned. Unless you had that additional grand for his own Mola-Mola version. Or wanted to bank on the eventual launch of lower-priced variants in more basic enclosures which would seem nearly predestined.
