Hypex NCore 400 Amplifier
Enter a great Class D amplifier from the Netherlands.
Article By Jeff Poth

  The crew at Hypex has been making class D amps for a long time- lead designer Bruno Putzeys designed the "Universal Class D" topology at Phillips, and Hypex licenses it for use in their own products (Phillips owns the patent). Hypex has had a successful run with this technology, my own amplifier uses their 400W (into 4 Ohms) boards, and I’ve been very pleased with it. As time rolls on however, improvements have been identified and Hypex has released a new, higher-end variant on class D, designated "NCore". The UCD line is still active and Hypex has a variety of interesting plate amps, DSP, and other components with and without amplification attached, all very well engineered.

My good friend decided that he wanted more oomph than his receiver was providing and because his speaker setup matched his space so nicely, he decided to go with an amplifier upgrade to achieve that. With a box of doughnuts in hand, he and our mutual partner in crime came around to my workstation... errr... kitchen table with a couple boxes of parts beyond the doughnuts, including the Hypex Ncore 400. The Ncore 400 delivers up to 400W into 4 Ohms, though that is dependent upon the power supply. These boards are intended for DIY'ers and are meant for use with Hypex switch mode power supplies. Normally the Ncore 400 is used with its sister supply SMPS600 -- the combination fit nicely to make compact monoblocks. In some cases alternative supplies may be used; for example when a compact stereo amplifier is desired, requiring a single larger supply (the SMPS 1200). We wanted a stereo amp, and it took some extra efforts, we had to do a fair amount of splicing and careful routing to achieve a good setup with this modification, but in the end all worked out well.

This thread and this thread within AudioCircle discussion board contains the diagram used for cross-coupling from the intended SMPS600 to the SMPS1200.

Notes on switch mode supplies:
Switch mode supplies are the most common type of power supply in modern electronics because they are by far the most efficient type of power supply, regulating the wall voltage to appropriate outputs utilizing a high-frequency switching arrangement. This allows for them to be small, generate limited heat and have excellent regulation performance when properly designed and implemented. Unfortunately, often they are not properly designed and implemented and the result is a lot of radiated high frequency noise. This noise contaminates both the device utilizing the supply and other devices connected to the same mains supply. Isolation transformers can be helpful when you’re stuck with this type of supply - phone chargers and other small electronics will often have noisy power supplies and inexpensive commercial isolation transformers on your non-audio gear can reduce the noise they radiate onto the main power lines, yielding better power for your gear. The Hypex supplies are properly engineered, so don’t exhibit this type of issue the same way. Whether they are ultimately as good or better than a proper linear power supply is debatable- some people prefer low-noise but unregulated supplies for main rail voltages, or linear supplies in general over switch mode. For me, I’m a little old-school, and I prefer big transformers in my gear over switch mode.

Back To Business
Binding posts and IEC inputs used were Furutech models along with Cardas XLR inputs. The case was made by Silicon Ray, and was solid and a good value, though the connector holes were not aligned. Altogether this was a fairly straightforward build process, though we moved rather slowly over a couple sessions (and some meaningful time/arterial plaque invested at the local Korean BBQ buffet... Thanks!) We took our time to make sure the power supply adaptation was correct and we made the right decisions in the build and to optimize the fairly pricey componentry. The case was pre-drilled for the modules, and as homework after we figured out the layout, my friend took the case home and drilled new mounting holes for the power supply. The small case is a tight space to work in, and we used epoxy to mount tie-off points to help keep the wiring secure and routed for minimal noise. To allow the epoxy to adhere properly, the finish was sanded off.

We carefully routed the input, speaker output, and power supply wiring around the boards, to ensure low potential for noise pickup. Between the twisted pairs and shielded input wire, we had no noise issues whatsoever.

Power supply wiring was pretty simple, utilizing high-current push-in connectors for the multi-wire junctions. These connectors were nice to work with and made very solid connections with tinned solid core leads. The alternative would have been terminal strips where space was at a premium, or wire nuts which have other shortcomings. Multiple twisted pairs were used for the main rails to keep radiated fields and wiring harness inductance to a minimum, and the lower current, lower voltages were hooked up as made the most sense from a layout perspective. An amp like this has multiple connections from power supply to amplifier circuit, to drive not only the main transistors responsible for the output voltage, but also to drive the input circuitry and class D oscillator/etc. Some class D amps, including the Hypex UCD, have these connections as optional- they can derive the needed voltages onboard from the main rails. The single main supply arrangement is convenient but best noise and amplifier performance is achieved by having multiple well-regulated supplies for all needed voltages. While it’s hard to tell from the picture, we used as much of the case height as possible to avoid interference in the power supply wiring, and got everything squeezed into the space available without issues. Fortunately these are DC supplies, not AC wiring, so we can allow for relatively tightly-bunched bundles as shown. Often these are routed in one overall bundle, but I prefer to keep things a little separate. The mute switch is on the back panel, to maintain the clean look of the faceplate.

All was well upon hookup- and the overall character was similar to my UCD amplifier- which is a very good thing, as my UCD is an excellent amp. We enjoyed some DVD concert content and CD music, but as this wasn’t my amp it was not to stay in my home for prolonged evaluation. Because it was only here for a short time I won’t endeavor to compare the sound of NCore to UCD, though user reviews are very positive online. The amp is pulling very smooth, clean, powerful sounding service in my friend’s rig and he’s happy with the upgrade so we’re calling this one a win.

Parts List
1. Amplifier Module: Hypex Ncore 400 - 2 modules

2. Switch Power Supply: Hypex SMPS1200/400 - 1 MOdule

3. IEC Input Plug: Furetch FTECH-65010 15A 125V/ 10A 250V AC Inlet Male, Rhodium, solder lug

4. XLR Connectios: Cardas CM F XLR, Chassis/PCB Mount, XLR Jack, FEMALE . 2 Connectors

5. Speaker Binding Posts: Furetch FT-809 Torque Binding Posts - Gold Plated 2 pairs

6. Case: RE2507-NC enclosure for 2 channels Hypex NC400 (Mounting re-drilled manual - re-orientation of the amplifier module and push PSU to the front of the aluminum case) link

7. Mute Switch: SPST Mini Toggle Switch link

8. Custom Molex Module for NCore400:

  (1) Molex header - Mouser Part # 538-43025-1200
       Manufacturer Part #: 43025-1200 Manufacturer: Molex. 2 modules link

  (2) Molex Wire Housing - Mouser Part #: 538-46235-0002
      Manufacturer Part #: 46235-0002 Manufacturer: Molex
      Description: Headers & Wire Housings 20-24FEM 30AU LWFRC
      Reel of 12000. 24 wire housing needed

  (3) 20 AWG insolated solid connection wire in Black, Blue, Red, Green, White, Orange and Gray

9. Wire: Hookup wire - DH LABS Silver Sonic 14 AWG. BLACK and RED Hookup Wire

10. Amplifier Stands: Four quantity Penn-Elcom F1696 rubber cabinet foot 1" D x 1.25" H.

Amplifier Module Features
All-discrete op amps with proven "real circuit" linearity well beyond that

Specifications
Output power 400W @ 4 Ohms
Characterized from open circuit down to 2 Ohm.
Lower load impedances are allowed, 24A current limit
SNR: Unweighted, min 124dB re full power, 101dB re 2.8Vrms
Output Impedance: 0.7 milliOhms (corresponds to a DF of 11000)
PSRR: Better than 85dB
Price: €325

Manufacturer
Hypex Electronics B.V.
Kattegat 8
9723 JP Groningen
Netherlands

Voice: +31-(0) 50-5264993
Website: www.Hypex.nl