This updated version of Lynx’s mastering converter offers a much improved touchscreen, a host of new filtering options — and the best D‑A converter performance we’ve ever measured!
When launched in July 2012, Lynx’s Hilo converter established a new benchmark level of performance that has endured for over a decade. Now, the company have raised that bar once again with a new, substantially updated version: the Hilo 2. At first glance, aside from a fashionable dark‑grey colour scheme replacing the original silver, and the 2 suffix being added to the name, the new model is visually indistinguishable from the old. But much has changed beneath the skin, all aimed at eking out even higher technical performance and delivering enhanced usability and functionality.
Overview
Users of the original Hilo will immediately feel at home, as the operation and connectivity are largely unchanged. This remains a two‑in, six‑out, mastering‑grade A‑D/D‑A converter, combined with an internal 16x16 digital routing matrix. The front‑panel touchscreen provides direct control and display functions, but a Mac/Win computer app can be used for remote control.
The front panel remains very minimalist, with just a standby on/off button, assignable rotary volume control, and quarter‑inch headphone socket. As before, every aspect of the machine’s configuration and operation is controlled through a large, colour touchscreen, but this 480x272‑pixel display is a major upgrade: now an IPS (in‑plane switching) type with capacitive touch‑sensing, it has been totally redesigned to be more responsive to touch, brighter, and with improved off‑axis viewing.
In my review of the original Hilo (https://sosm.ag/lynx-hilo) I noted that “my only difficulty was with the touchscreen interface, where my podgy fingers only needed to be slightly off centre of the relatively small virtual buttons on the routing pages to either get no response or activate the wrong source”. I had no such difficulties with the Hilo 2, which responded quickly, precisely and reliably to my every prod without my even thinking about finger placements. So, this new screen is a very worthwhile upgrade!
The new touchscreen is a significant improvement over the one used in the original Hilo.
As far as I can tell, the Hilo 2’s current firmware (v1.3, released August 2024) is derived from the most recent version for the previous model (v8.13), and the core functionality and graphics appear almost identical. One useful key difference that I spotted early on, though, is that the new converter hardware can be configured with a wide range of different linear‑ or minimum‑phase filtering modes. The excellent, 70‑page manual explains these different modes well but, as a quick overview, the minimum‑phase options mimic ideal analogue filters, complete with their potential for ‘time smearing’ and altered waveshapes due to different phase‑shifts versus frequency.
The linear‑phase options maintain the phase relationships between different frequencies (and thus preserve waveshapes), but introduce pre‑ringing to the impulse response (ie. the filter creates an output before the wanted signal arrives, which isn’t something that can happen in nature!). Some people argue that pre‑ringing is audible and accounts for the difference in perceived sound quality between analogue and digital systems. For those who subscribe to this view, the availability of minimum‑phase alternatives will be appealing.
Both ‘fast’ and ‘slow’ options are available for both types of filter, referring to the steepness of the filter slope. The fast filter modes essentially provide a slightly wider and flatter signal bandwidth, while the slow options start to roll off a little earlier but much more gently, and the impulse response ringing is of shorter duration and reduced amplitude as a result. Interestingly, there’s also a linear‑phase mode with an ‘apodising filter’ setting (see the ‘Apodising’ box).
Inputs & Outputs
Other than the front‑panel headphone socket, all I/O connections are made on the rear panel and are identical to the previous model. Stereo line‑level electronically balanced analogue connections are on XLRs, with monitor outputs on a pair of quarter‑inch TRS sockets. As with the original version, the analogue line input and output reference levels are adjustable, reaching 0dBFS for signals between +18 and +24 dBu to match professional equipment, or 0 to +6 dBV for consumer gear. The monitor outputs are also configurable for a maximum level of either +24 or +10 dBu.
The expansion slot accepts USB, Thunderbolt or Dante cards, with USB being the most affordable option.
Digital audio in and out is either via XLRs for AES3 or RCA phonos for S/PDIF. Both formats are active simultaneously for the outputs, but only one can be selected at a time for the digital input. A pair of Toslink optical ports is also provided and can be configured either for ADAT or optical S/PDIF formats. All the usual sample rates are supported up to 192kHz, although the ADAT interface only supports single‑rate (eight‑channel) and double‑rate (four‑channel) modes. Similarly, the USB interface provides 16 channels at single and double rates, but only eight channels at quad rates. Word‑clock in and out is available via a pair of BNC connectors, and power is through the ubiquitous IEC mains inlet (100‑240 V AC), or a four‑pin XLR for external battery power (9‑18 V DC).
As with the original model, an optional ‘LSlot’ interface card can be installed providing up to 16 channels in (usually configured as eight stereo sets) and 16 more out, via a USB, Thunderbolt or Dante connection to a computer. Drivers are available for the Thunderbolt and USB options, for both macOS and Windows. The Hilo 2 operates as a Core Audio device using USB on a Mac, and supports both WDM and ASIO on Windows. The Thunderbolt interface requires a dedicated Lynx driver on both platforms.
Screens
Most of the time, the display screen shows audio signal levels in various ways, and there are four options. The All I/O view does as it says, using two rows of vertical bar graphs to show the current signal levels on each and every input and output. The Horizontal view presents two larger horizontal stereo bar graphs, configured to show selected input and output levels. Perhaps the most attractive option is the Analog VU, which is a virtual pair of classic VU meters whose sensitivity is adjustable between ‑3 and ‑30 dBFS for 0VU. Again, any input or output source can be assigned to feed the meters. Lastly, there’s an RTA (real‑time analyser) option, with two rows of vertical bar‑graphs indicating the stereo level across 30 frequency bands for any selected input or output. The sensitivity is also adjustable in 3dB steps.
The Audio screen provides access to functions like the desired sample rate and sync source, analogue line input and output reference levels, Toslink optical interface mode (S/PDIF or ADAT), selected digital input source (AES or S/PDIF), and SRC on/off for the digital input (synchronising an external digital source to the Hilo’s current clock rate).
A System page accesses functions like the display language, backlighting, USB modes (eight or 16 channels), digital filtering modes, and rotary control assignments (normally it controls the monitor and/or headphone outputs, but it can be used to control other outputs or groups of outputs). Information is also displayed here on serial and firmware numbers, and factory defaults can be restored.
Particular system configurations and routings can be stored and recalled as Scenes on another menu page with eight options altogether; four are factory settings, and four are user configurable. The last menu page allows signal routing from any combination of inputs to any number of outputs, allowing multiple sources to be mixed and fed to multiple destinations, if desired, with adjustable signal levels. The setup process involves highlighting an output and then selecting (or muting) the required input(s). It’s easier than that might sound, and routing is performed as stereo pairs of channels. Helpfully, selected sources can also be summed to mono, or either channel can be routed to feed both output channels, if needed.
Bench Tests
The best modern converters really are now performing on the very edges of human perceptibility, meaning that incremental technical improvements are more easily identified through test‑bench measurements than through conventional listening tests. Regular readers of my converter reviews will know that I value the AES17 dynamic range test as a good overall indicator of converter performance. I have found it to give consistent and reliable quantitative assessments of converter performance that tally closely with my personal subjective impressions. This is probably because, in order to achieve a good AES17 score, every single aspect of the converter’s design and manufacture has to be optimised, including the analogue circuitry, the grounding arrangements, the power supplies (particularly the analogue/digital supply isolation), the clocking arrangements, digital stream recovery, and more. The smallest technical weakness in any area very quickly degrades the AES17 measurement.
When I reviewed the original Hilo, it scored 121.3dB (A‑weighted) for the A‑D converter and 120.5dBA for the D‑A conversion. Both are excellent figures which placed the Hilo comfortably within the top 10 of all the converters I’d measured at that time. I still rate anything above 118dBA as being of genuine professional mastering quality, so to have achieved this standard 12 years ago is highly impressive. Nevertheless, converter chip manufacturers have continued to improve the performance of their devices, and product manufacturers continue to build converter systems that are capable of extracting all the potential performance of these newer chips.
These are exceptional figures, genuinely pushing against the boundaries of what is possible in a practical commercial product, and Lynx are to be congratulated on their striking achievements.
This is all clearly evident in my bench tests of the new Hilo 2. In my tests, this newer model gained 2dB of performance on the A‑D side, measuring an exceptional 123.1dBA. That’s second on my list only to the incredible RME ADI‑2 Pro (124dBA). The D‑A side exhibited an even greater improvement, reaching a whopping 128.1dBA, making it my new leaderboard winner — 2dB better than the Merging Hapi interface, which was the previous leader. These are exceptional figures, genuinely pushing against the boundaries of what is possible in a practical commercial product, and Lynx are to be congratulated on their striking achievements.
This Audio Precision chart illustrates some of the available D‑A filter mode options. The red, orange and pink curves are minimum‑phase types while the blue and purple curves are linear‑phase. The fast modes start to roll‑off steeply from around 22kHz, while the slow options start attenuating very gently from about 16kHz. The default option of Linear Fast gives greater attenuation at the Nyquist frequency (48kHz) than all other options apart from the apodising filter (green).
Similar improvements are apparent across many other bench test measurements too. For example, the THD+N figure for the analogue line inputs is 3dB better (now ‑117dB), while that for the line output is 11dB better (‑120dB). Crosstalk is also improved for both line input and output, but especially the latter, which is 8dB better at ‑143dB (at 1kHz).
I couldn’t find any significant changes in the performance of the monitor or headphone output sections, which both achieved THD+N of ‑107dB and crosstalk around the ‑135dB (at 1kHz) mark. Perhaps not quite as impressive as the main line outputs, but still a very high standard.
Impressions
The new Hilo 2 undoubtedly delivers an impressive step up in its technical performance compared with the original model, regaining the top spot in my own tested converter league table and highlighting the current state of the art. This is to be highly commended.
Many of the ‘essential’ items I described in a ‘wish list’ of functions in my review of the original model have also been incorporated through various firmware updates over the last decade, and have been carried over to the Hilo 2. For example, things like adjustable VU meter sensitivity and ADAT channel selection. Sadly, most of my other suggestions haven’t (yet?) been implemented and, given the open‑ended development promise of the original concept and 10 years of development time, I found this disappointing. I’d still like to see, for example, basic monitor controller functions, stereo width manipulation, L‑R channel swapping, True‑Peak and Loudness metering, and a cross‑point matrix display option for viewing and setting signal routing paths.
Nevertheless, the Hilo 2 is a phenomenal, benchmark‑setting professional converter that offers stunning sound quality, superb features, great versatility, and even easier operation than its forebear. The Hilo 2 is ideally suited as the heart of any professional mastering suite, transfer room, or high‑end audiophile’s system, delivering standard‑defining audio quality in a wonderfully easy to use and configure format. The best just got better.
Apodising
The filters on offer include an apodising option, intended to reduce the pre‑ringing inherent in linear‑phase filters.
Apodising filters have been used in spectral analysis functions for decades as a way of reducing the effect of the abrupt start and end of analysis time windows. In digital audio applications, an apodising filter is employed to reduce or remove linear‑phase filter pre‑ and post‑ringing that is caused by the D‑A reconstruction filter and that is already embedded in the digital signal by the A‑D’s linear‑phase anti‑alias filter.
In simplistic terms, an ‘apodising filter’ is essentially a specific type of minimum‑phase low‑pass filter, which is critically designed to place its first deep null at the Nyquist frequency, but there’s rather more to it than that.
As we know, digital audio signal paths inherently involve both anti‑alias and reconstruction filters in the A‑D and D‑A converters, respectively. In any system containing a series of filter stages, the system’s overall frequency response is the product of the individual responses of each filter. So, for example, if the chain contains two first‑order (6dB/oct) filters in series with the same turnover frequency, the overall response will be a second‑order (12dB/oct) filter.
However, in the time domain, the overall impulse response of the whole chain is defined by the convolution of the individual filter responses, the significance of which is that it’s possible to design a filter which, through convolution, exactly counteracts the time‑domain characteristics of standard linear‑phase filters. This is the ‘apodising’ filter and, when introduced into the signal path, the overall system’s impulse response becomes shorter and smaller than that of any of the individual filters. In this way, it’s possible to almost completely remove both pre‑ and post‑ringing associated with conventional linear‑phase filters.
Naturally, there are trade‑offs; the most significant is that the apodising filter has to start rolling off slightly lower in order to achieve that deep first null at the Nyquist frequency. But we’re really only talking from roughly 19.5kHz instead of 21.5kHz, in a 44.1kHz sampled system, and I think that’s a very small price to pay for a fully corrected time‑domain performance — and in systems with double or quad sample rates there’s no compromise involved at all! Secondly, as the apodising filter is still a minimum‑phase low‑pass filter, there will still be some post‑ringing, but this is natural and, as it generally falls within the human temporal masking range, inaudible.
Apodising is a very clever and proven practical solution, first described for digital audio applications by Peter Craven back in 2004, and I remain baffled, 20 years on, that so few manufacturers of digital products employ it — it’s good to see it as an option in the Hilo 2.
Alternatives
The only direct alternative, in terms of both core functionality and class‑defining audio quality, is RME’s ADI‑2 Pro.
Pros
- Stunning audio performance.
- Redefines the benchmark standard of converter performance.
- Greatly improved touchscreen.
- Immensely versatile and impressive converter/router system.
Cons
- This sort of quality costs!
- Signal processing and metering functions haven’t yet expanded to meet the open‑ended promise of the original design.
Summary
The Hilo 2 redefines the state of the art in converter performance, while retaining all the much‑loved versatility and capability of the original.
Information
USB version £3769, Thunderbolt 3 £4355, Dante £4459. Prices include VAT.
Source Distribution +44 (0)20 8962 5080.
Hilo 2 including: USB card $3599; Thunderbolt 3 card $4199; Dante card $4299.
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