I would like to take this opportunity to list some random notes Re. my James Romeyn Hypex Professional Build Service, specifically my Hypex NCore NC400 Stereo and Hypex NCore NC400BTL (Bridged Tied Load) high end audio power amplifiers.
I respectfully request readers allow me to open w/a singular shameless plug. Alan Silverman of Arf Productions! Studio in Brooklyn has won two Grammy Awards. Alan is one of our happy and satisfied NC400 owners, and he paid full price. I should look up Alan’s exact words via email, but suffice to say Alan typed something like, “NC400 changed the way I listen to music.” Interestingly, Alan’s first impression was puzzlement, NC400 sounding so different than anything else he heard prior, that he was not sure what to make of it. Alan might be the last person on earth to make a quick or snap judgment concerning audio performance, the polar opposite of some audiophiles. Shameless plug closed.
Since designing and releasing the Stereo chassis several years ago, regular mono blocs ceased production, not to be confused w/NC400BTL Bridged Tied Load mono bloc. Our Stereo amp has 1200W PS, exactly twice the 600W PS in the regular/discontinued mono blocs.
NC400 Stereo: $1490/ea, 200/400/600W @ 8/4/2 Ohm, 1 Ohm minimum
NC400BTL mono, same chassis as Stereo: $2980/pr, 400/800/1200W @ 8/4/2 Ohm, 1 Ohm minimum, includes free internal optional foil capacitor across speaker output per Hypex recommendation, outperforms Stereo version at all power levels, even fractions of a Watt.
I have shipped the above amplifiers to happy and satisfied clients all over the globe. NC400 works perfectly well w/50 Hz or 60 Hz AC mains voltage from 110V to 240V.
Since 2015 we installed IEC input w/Rhodium plated contacts, an audible upgrade. Owners w/the earlier nickel plated IEC can upgrade for $7 plus round trip shipping, turnaround time usually one business day. Also since 2015, we installed Hypex’ so-called nAmpon (Negative Amp On) switch on the rear panel, easily accessed in the top hole between the XLR jacks. Up = normal play/20W idle current, Down = input mute/4W idle current. Users can swap inputs in the down position.
How reliable and how bulletproof is NC400? For about thirty seconds I saw someone accidentally short the speaker outputs of his two NC400BTL (again, 1200W @ 2 Ohm, 1 Ohm minimum). One NC400BTL made a sequential “click” sound. Not only was nothing damaged, not even the PS fuse blew in either amp. I suspect most amps would have incinerated output transistors in one or both amps, and possibly even one or both PS transformers. The only error more brutal I can imagine is applying AC mains voltage to the speaker outputs. NC400 is among the most bulletproof amps extant.
Hypex designer Bruno Putzeys stated the component w/the shortest shelf life is the largest power supply capacitor. After twenty years of use, Bruno stated this capacitor may change its value but would likely still be within OEM specs.
Based on the above, let’s estimate a twenty five year shelf life for this capacitor. I estimate, in today’s dollars, replacing this capacitor out of warranty would cost about $125/25 years = $5/year service cost + AC mains voltage (very low).
No offense to competing Class D amps, but one gets the impression that Hypex shall be around for service for many years.
NC400 built today might need its PS capacitor replaced in 2042. Presumably, a similar exercise w/a typical Class A and/or Class AB amp would look less attractive.
Electrolytic power supply capacitors have two shelf life specs, “dry” (no voltage applied/not in use) and “wet” (voltage applied in use in circuit). The latter is generally about 1/3rd greater than the former, meaning the above described power supply capacitor lasts about 1/3rd longer w/AC mains current applied to NC400. I would suggest flipping the nAmpon switch up during waking hours and down during sleep time. Of course, always unplug AC mains to NC400 during electrical storm or threat of same.
Of all NC400s we built, only one client demanded RCA inputs. Bruno is adamant there is no good reason to employ RCA input instead of NC400’s fully balanced input, even w/unbalanced source. Per Bruno, the following unbalanced source applications almost match the performance of a fully balanced source:
Unbalanced source RCA > quasi-balanced IC > NC400 XLR input, or close second...
Unbalanced source RCA > RCA/XLR adapter > balanced XLR IC > NC400 XLR input
Avoid the following applications, for which no good reason exists to employ:
Unbalanced source RCA > unbalanced RCA IC > RCA/XLR adapter > NC400 balanced input or...
Unbalanced source RCA > unbalanced RCA IC > NC400 RCA input
Plug your new NC400 directly to the AC mains power, using no filtration or so-called purification device, which degrades performance.
NC400 has huge current capacity. Even @ 8.5 lbs, it supplies as much or more current than 100 lb Class AB amps. The worse/more difficult is the speaker load, the more does performance improve by lowering speaker cable series resistance. Ideally, NC400 owners should view graph depicting their speaker’s impedance and phase angle across the full bandwidth. I found NC400 to supply so much current that some applications benefit with less series resistance in the speaker cable than what is recommended in online calculator for this purpose.
OK, I lied. Shameless plug #2 and final: for decades I preferred Stan Warren’s (the S of PS Audio, P being Paul McGowan) original speaker cable recipe, which Stan personally gave me, and is equivalent 9AWG. I found cases where NC400 audio performance improved w/6AWG cables, even though online calculator recommended 9AWG. Since then I devised my own speaker cable recipe, 6AWG equivalent, that handily outperforms Stan’s original 9AWG recipe, whether the amp is an ultra low current tube OTL or ultra high current NC400 beast. Originally I sold this cable w/custom DIY solid copper terminals for only $220/pr 6 feet, but since that time I found that Rhodium terminals are indispensable, increasing the price to $320/pr 6 feet (longer lengths only moderate price increase). I unequivocally recommend auditioning these cables for any application, but especially for NC400 owners and even more so if the speaker drops below 5 Ohm, which is almost every speaker. 45-day return w/full refund in same condition as received.
