This review page is supported in part by the sponsors whose ad banners are displayed below

Reviewer: Srajan Ebaen
Financial Interests: click here
Source: APL HiFi NWO 3.0-GO; Ancient Audio Lektor Prime; Yamamoto YDA-01
Preamp/Integrated: ModWright LS-36.5 with PS 36.5

Amp: 2 x Audiosector Patek SE; First Watt F5
Speakers: Neeper Acoustics Perfection One [on review]; Acoustic System International Tango
Cables: Acoustic System International Liveline interconnects; Crystal Cable Ultra and Reference power cords; Acoustic System International Liveline power cord [on loan]
Stands: 2 x Ikea Molger, with re-purposed assorted Ikea butcher block platforms
Powerline conditioning: 2 x Walker Audio Velocitor S, with custom AudioSector 1.5KV Plitron step-down transformer with balanced power option for 120V gear
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; extensive Acoustic System resonator tuning throughout the house
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: €6,000|€8,000 for P10|H10 respectively

Simple is better. Einstein said so. As did Nelson Pass. Naturally, that sentiment is shared by many, across many very diverse disciplines. If you too subscribe to this notion, consider Hegel's Norwegian flagship P10. It puts all of 2 FETs and one or two resistors in its fully balanced signal path.* Yes, what we have here is a single-stage, zero-feedback single-ended circuit. But unlike typical SETs, this one's not a power amplifier. It's a line stage. And unlike typical SETs, it sports vanishingly low THD. Hegel in fact claims complete and utter elimination of any higher-order artifacts above the 3rd, period. Credit obsessive parts matching for that annihilation. Hegel apparently ordered 30,000 exotic Toshiba parts and returned 29,700, rejecting all that didn't pass the desired tolerances. The remaining 300 were sorted into 16 categories to arrive at perfectly matched pairs. That's why there'll be only 30 units each, of the P10 and its matching H10 power amplifier. Such
hard-nosed rejection ratios and endless testing don't lend themselves to normal mass production cycles. Hence this review is about two very exclusive products.

This number ambiguity is because of relay-switched resistor attenuation. To achieve the desired signal strength, one (or two resistors together) create the desired value. The volume control visible to the user is a standard pot whose position codes an A/D converter that triggers the specific relay which selects the necessary resistor configuration.

The H10's voltage gain stage mirrors the P10's. It then adds a bipolar current buffer with patented feed-forward error correction* to produce 2 x 300 watts into 8 ohms, 570 into 4 and 1000 into 2. The load stability of the amp is a crushing 0.5 ohms. On further specmanship, channel balance is said to be better than 0.1dB. Frequency response deviation less than 0.2dB within the audible band. Phase response within +/- 2 degrees. Cross talk better than -100dB. S/N ratio better than 100dB. Damping factor above 1000, i.e. ultra-low output impedance. And IMD less than 0.01% on the 19/20kHz intermodulation test. The power toroid is a massive 2400VA affair with dual-mono windings. Power supply capacitance adds up to 320,000uF. And to arrive at the very substantial power figures, the output stage runs 56 high-speed and gain-matched bipolar transistors of the 15A/200W kind.

Once we return to the 6-input relay-switched remote-controlled preamp, its low-level specs get more radical yet. 0.05dB frequency response deviation. Less than 0.5 degrees phase shift. Cross talk better than -100dB. Noise floor below -140dB. And IMD below 0.004%. While the promised fruits of simplicity are thus exceptional accuracy and ultra-low distortion, arriving there wasn't simple. Just consider the photo of the relay resistor network below.

Hegel's dynamic error correction is dubbed SoundEngine and carries US patent 6,275,104B1 awarded to Hegel founder and chief engineer Bent Holter. It is claimed to cancel class A/B-type crossover distortion while avoiding any kind of global negative feedback, relying instead on "local and adaptive laser-trimmed feed-forward technology". As Bent explained to me in person at the Guangzhou show, this parallel circuit is mostly inactive and prompted only when specific parameters 'written' into the analog threshold detector trigger it to apply correction which is then added to the signal in real time. Bent's background includes working in radio broadcasting, recording studios, transistor manufacture and playing the clarinet. He stated plainly that if necessary, he could design Hegel transistors from scratch. Actual in-house fabrication of course would be prohibitive but he truly understands how transistors are made and work from the inside out.

It is this intimacy with them that led him to the isolation of specific performance parameters which even companies claiming to match transistors, in his opinion, don't test for. Holter believes his extreme test protocol to be unique but he reiterated how to the extent pursued in this Special Edition product, it is frustratingly inefficient, laborious and impractical.
To see Bent Holter's sketch of the SoundEngine circuit, click on the above graphic

Both machines offer balanced inputs as standard. For single-ended users, there are RCA i/o ports on the preamp, RCA inputs on the power amp. In short, go in and out as you please. It won't affect ideal operation. The H10 sports twinned speaker terminals for easy biwiring. And because of class A/B operation, there are no heat or green issues.

The P/H10 combo is Hegel's 10th Anniversary can-do celebration of its standard P4A/H4A models, but 'extremized' as far as the firm knows how to. Alas, that doesn't include the finish. The 30 ultra-tolerance pairs are only available in black, not silver. It's not just more stringent parts matching per se though. Both 10s benefit from entirely new input stages running JFets instead of bipolars; different transformers and more. And their core circuit minimalism simply isn't possible without the extravagant precision matching.

To summarize the P10 concept, Hegel aims for a passive preamp's transparency with the power of an active. The recipe combines an overbuilt power supply and sophisticated new custom attenuation scheme with the simplest possible voltage gain - one stage, single-ended, no feedback but fully balanced.

The H10 borrows the P10's FET voltage gain section and marries it to a massively paralleled current buffer with upgraded bipolar transistors over the H4A. With its quite hulking dimensions of 21 x 43 x 55cm (HxWxD), this 45kg stereo amplifier is a true power house. Its load stability into a half ohm should embrace even the most dastardly loads irresponsible speaker designers have brought (or dream of bringing) to market. This is a high-current amp then to drive anything with. Considering how it consumes only 100 standby watts, the operational bias is quite low. Fry your eggs in the pan.

Classic class A bias is claimed unnecessary due to the zero-crossing distortion elimination of Hegel's SoundEngine correction circuit. The Scandinavian-chic chassis doesn't scream heat sinks from hell or vertical space heater. It'll be comfortably at home not just in man caves. And that's precisely what one imagines Hegel's cosmetic minimalism goes after: understated elegance hiding thoroughly hi-tech guts. Put differently, hulking fins and snazzy meters might attract more attention but the plain appearances here are deceptive. Don't judge with your eyes. Or do. Once you flip up those plain bonnets to contemplate the internal parts density...