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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: Esoteric UX-1;Yamamoto YDA-01
Preamp/Integrated: ModWright DM-36.5; Esoteric C-03, Wyred for Sound (on review)

Amp: FirstWatt F5, ModWright KWA-150, Octave MRE-130, Yamamoto A-09S
Speakers: Acoustic System Tango R
Cables: Acoustic System Liveline interconnects, speaker cables and power cords

Stands: 2 x Ikea Molger with Ikea butcher block platforms and Acoustic System footers
Powerline conditioning: 2 x Walker Audio Velocitor S
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; full-house installation of Acoustic System resonators, noise filters and phase inverters; Advanced Acoustics UK Orbis Wall and Corner
Room size: Sound platform 3 x 4.5m with 2-story slanted ceiling; four steps below continues into 8m long open kitchen, dining room and office which widen to 5.2m with 2.8m ceiling; sound platform space is open to 2nd story landing and 3rd-floor studio; concrete floor, concrete and brick walls, converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse
Review Component Retail: ca. €3,200 for CDP, €2,600 for amp (depends on country and VAT offsets)

Cool Nordic looks, heady engineering!
Perusing Hegel's web pages, one comes across many an item™. Cynics could recall the secret circuits wars of the 80s. Then every audio electronics maker concocted ever more outrageous acronyms for what essentially were the same old topologies. It's a trend best forgotten.

Here there is some real distinction. It's simply mixed up with laudable but certainly not unique solutions which still get their own Hegel Speak polish. Let's begin with the CDP4A. As Hegel does for all its CD players, it runs an AC mains input filter to purify wall power. Then it adopts a low-noise voltage reference system where "many individual voltage regulators" optimize the dual-differential (fully balanced from converter to output) signal path between multilevel 24-bit 352kHz DAC, master clock and output stage. We thus get single-ended and true balanced outputs. For off-boarders, there's a transformer-coupled RCA digital port. Very unusual for such a small firm, Hegel implements its own CD servo decoder board for the chosen Sony transport and has done such add-on digital engineering since 2002. Industry convention for even far larger firms (with really expensive players) is to buy their transport mechanisms with associated servo circuits from OEM suppliers like Philips, Sony, Matsushita and Daisy and leave those alone. Not our Norwegians.
"When reading the digital data from a CD spinning at 200-500 revolutions per minute, the laser system has to dynamically lock to this spiraling data track with micro-tolerance precision. It must do so while the CD spins eccentrically both horizontally and vertically (due to CD stamping tolerances, the data track is never physically centered on the disc's geometrical center). To track these orbital offsets, three different servo motors move the laser head horizontally and vertically. These motors rely on large dynamic current flowing through their circuit boards to keep the laser system fixed precisely on the extremely narrow data track wobbling past.

Power supply for CD servo
Analog filter
On/off power relay control
Digital filter, jitter eliminator and DAC chip
The following five thumb nail links are of the H100 integrated amplifier. The first six belonged to the CDP.
Micro controller for buttons and display
Transport mechanism
Bipolar output transistors
SoundEngine board
Input switching relay
Line-level outputs and speaker relays
Micro controller for volume and input

"To read this 0.4 micrometer track, an infrared laser diode illuminates it, light-sensitive photo diodes receive back the reflections from the pits and lands. These response currents are far smaller than the large servo motor currents. Contrary to popular belief that CD is an all-digital system, the current outputs from the photo diode readers are high-frequency analog signals. It is these tiny photo diode currents which are disturbed by the large servo-motor currents. This disturbance must be avoided for error-free high-frequency analog optical response. The design of the photo diode amplifier circuits and their circuit board layout is thus extremely important to preserve the highest possible S/N ratio for the CD signal. And, error-free read-in is vital because CDs are processed in real time. Lost data cannot be retrieved."

Hegel responds to these electro/mechanical demands with its own servo decoder boards. They also implement a special master clock with a "very stable clock frequency and the lowest possible jitter (<10ps)". Contributors to master-clock jitter include power supply noise, clock oscillator topology, quartz crystal resonator quality, clock driver circuit and circuit board layout. "Most CD players' master clocks are located at the CD servo-decoder boards to suffer unstable frequency and high jitter from exposure to high levels of signal and power supply noise. In addition, many use a S/PDIF serial digital interface from the servo-decoder to DAC boards. This increases jitter and decreases performance." That's exactly why expensive solutions separate the master clock generator. That's also why Hegel places their master clock generator on the DAC board. From there it is distributed to the converter chip and servo decoder.

When it comes to the popular asynchronous upsampling, Hegel believes it "converts jitter error into amplitude error" and prefers synchronized upsampling for its fully balanced syncroDAC™ implementation. The reconstruction filter is a "linear-phase" variant to maintain phase integrity of the signal. The subsequent fully balanced Linear Phase LineDriver™ output stage combines high current and low impedance to "drive all types of signal cables". All this nets very impressive published specs. S/N ratio is given as <-130dB, cross talk as <-100dB, distortion as less than 0.002% and IMD below -110dB (19kHz + 20kHz beat test). The output signal is 2.3V for both RCA and XLR, dimensions are 8 x 43 x29cm HxWxD and weight is 10kg. The CDP4Amk2 comes in either black or silver, with a glass-particle blasted and anodized solid aluminum front panel and matching controls, solid aluminum side rails and a brushed aluminum top cover.

For user-interface functionality, Hegel's CD player is more restricted than most. Front panel access controls are limited to two circular rocker buttons with three basic functions each. The metal remote's 12 identically sized buttons only cover play, prev, next, stop, fast rewind, fast forward and repeat while the mute and vol/ch +/- buttons are for the integrated. Those keen on display dim or off, direct track access, time remain options and such are out of luck. How the display shows pause, repeat track and repeat disc with those strange gaps and combination of small and capital letters is also a bit funky. It seems not quite in keeping with the elegantly understated appearance elsewhere.

For all its power and integrated amplifiers, Hegel engineering has patented their SoundEngine™ adaptive feed-forward "local error cancellation" system to increase dynamic range and lower distortion*. Not traditional negative feedback (this technology uses no global feedback of any sort in fact), it "cancels crossover distortion found in all class A/B amplifiers" to allow class A/B topologies "with the advantages of class A and without the draw backs of class A or class A/B technologies".

* In my prior review of Hegel's flagship preamplifier and amplifier, the technically curious can find just a bit more on the SoundEngine circuit.