Natty Norwegian
We put Hegel’s H160 amplifier to the test
Hegel is a Norwegian company which had a rather strange beginning. ‘Way back in 1988 Bernt Holter, a young electrical engineering student at the Technical University in Trondheim (NTNU), was paying his way through uni by playing in a heavy metal band called ‘The Hegel Band’.
As the band became more successful and started playing larger and larger venues, it needed more powerful amplifiers, so Holter decided to build them himself, using a new amplifier topology based on a circuit he’d developed for a thesis in which he’d proved that it was possible to reduce distortion in an audio amplifier without adversely affecting other performance parameters, in particular frequency response and damping factor (the circuit he developed is now trademarked by Hegel as ‘SoundEngine Technology’). Rather than build ‘one-off’ amps, he decided the circuit was so good it deserved to be built into fully commercial products, capable of being mass-produced, so Holter negotiated a partnership with one of the biggest telecommunications companies in the world, the Telenor Group, which is based in Oslo, Norway, but has mobile operations in 13 markets under its own name and in another 14 markets in partnership with VimpelCom Ltd. In all, Telenor manages more than 390 million mobile subscriptions.
Of course the new company required a name, so Holter decided on using his band’s name for both the name of the company and the brand name of the amplifiers. Thus it was that Hegel Music Systems came into being.
The equipmenT
Hegel variously identifies the H160 as either an ‘integrated amplifier’ or a ‘Music Machine’ depending on where you look on its website and although the latter label suits it the best, it doesn’t really describe exactly what it is, because as well as being an integrated amplifier, the H160 has a DAC built in as well. It would be better to call it a ‘Amplidac’ as this is the label that describes most precisely exactly what the H160 is and what it does, but unfortunately this word has yet to enter the audiophile lexicon, despite the attempts of Australian Hi-Fi’s editor to popularise it. ( I’ll get there in the end… Editor.) Essentially the Hegel H160 is an integrated amplifier with an inbuilt DAC that has both hard-wired inputs (analogue, digital and USB) and a streamer, so it can stream music wirelessly from any Apple AirPlay or DLNA device (though you do need to provide your own network—the H160 can’t do everything entirely on its own!)
As an integrated amplifier, the Hegel H160 is rated with an output of 150-watts per
channel into 8Ω (or 250-watts per channel into 4Ω) and has one balanced (XLR) input, one unbalanced (RCA) input and a single ‘home theatre’ (RCA) input. It also has two line-level analogue outputs (one fixed voltage, the other variable voltage) plus of course, speaker-level analogue outputs in the form of the usual colour-coded multi-way bananacapable terminals. They’re not on standard 19mm centres, so you can’t use dual Pomona banana connectors.
As a DAC, the Hegel H160 has six digital inputs: one coaxial digital input, three optical (Toslink) digital inputs, one USB (Type B) input and an Ethernet (RJ45) input. It also doesn’t use one of the ‘usual suspects’ ICs from Burr-Brown or Cirrus Logic, but instead uses an Asahi Kasei AK4396 192kHz/24-bit 128× oversampling delta-sigma device… one that has full differential SCF outputs, so there’s no need for Hegel to use any coupling capacitors.
As a Streamer, Hegel says on its website— and I quote—‘ You can also stream wireless music to it from devices with Apple AirPlay or DLNA’ but this is not strictly true, because you have to use the Hegel’s Ethernet connection to link to a wireless router, and it’s only after doing this that you can interface with UPnP and DLNA clients or Apple AirPlay. Note also that the Hegel H160 is a passive recipient of whatever music you send to it as data via Ethernet (or USB). It can’t request music from any of the components on your network, wired or wireless. Personally, I prefer this approach, because it means you don’t have yet another renderer in a system, meaning the renderers can be on other devices—devices that are more easily changed, upgraded and/or updated.
As you can see, the front panel of the H160 is beautifully simple and elegant: two large rotary encoders flanking a display with a deep ‘blue on black’ readout. The only other thing on the front panel is a standard 6.35mm headphone socket. Unlike most headphone sockets, lurking behind the one on the H160 is a full low-impedance, highcurrent headphone drive circuit. I tested this fairly early on in the reviewing process with every pair of headphones I had at my disposal, including the in-ear Sennheisers I use when I’m at the gym, and the H160 made every pair sound brilliant: no noise, no distortion, and more power than I’d ever need. Would that all amplifiers had headphone circuits this good!
Inside the amplifier are a multiplicity of what Hegel refers to as ‘technologies’ so you have ‘Dual Amp Technology’, ‘Dual Power Technology’, ‘Line Drive Technology’, ‘Masterclock Technology’ and others. I don’t know why Hegel calls these ‘technologies’ (maybe this is just an issue with the translation from Norwegian to English) but I think they’re more akin to being ‘features’ than ‘technologies’… which is not to say they aren’t great features. For example, let’s look at what ‘Dual Amp’ means: In most amplifiers the voltage gain stages and current gain stages are combined in the same amplifier section. Hegel’s ‘DualAmp’ approach splits the voltage gain and current gain stages into two completely different stages. According to Hegel’s Bernt Holter, this has significant advantages. ‘ First, the music signal goes to the voltage gain stage, amplifying only the voltage level of the music signal, and by doing only voltage gain in this first stage, we can use amplifier building blocks that are specially designed to do voltage amplification,’ he told me. ‘ Then the following current gain stage has only to do the current gain and nothing else, allowing us to use amplifier blocks that are specially designed to do current gain. Finally, there’s no feedback from the current gain stage to the voltage gain stage, which results in lower distortion and a higher dynamic range than normal audio amplifiers.’
Hegel’s ‘Dual Power’ approach ensures that the voltage gain and current gain stages are fed by completely separate power supplies. Hegel says it uses custom-designed toroidal power transformers with dual secondary windings, with each winding feeding independent high-speed rectifiers and high-capacity power supply capacitors so the voltage rails for the voltage and current stages are completely isolated from each other.
According to Holter, his ‘SoundEngine’ approach ‘ combines the advantages of Class-AB amplifiers and the advantages of Class-A amplifiers without any of their drawbacks and without any global feedback.’ The patented circuitry apparently cancels crossover distortion by using local feedback in combination with adaptive feedforward circuitry.
The ‘LineDriver’ seems to be a differential balanced output stage that has a low output impedance and a high-current capability, so if you need to run signal wires a long way you’ll get reliable, noise-free performance almost irrespective of the length or design of the cables you’re using. Of the other Hegel technologies inside the H160, there wasn’t sufficient information on the company’s website for me to understand how the company’s approach to, say, clocking, was different from other companies. One exception was the Hegel’s DAC technology.