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Prism Sound Lyra 2

USB 2 Audio Interface
Published September 2015
By Hugh Robjohns

Prism Sound Lyra 2

Prism Sound’s Lyra brings the quality of their Orpheus and Titan interfaces within reach of lesser mortals.

Prism Sound need no introduction, such is the company’s reputation in high-end converter technology. When Prism Sound released the Orpheus interface in 2008 it set new standards for quality, capability, and convenience, and a small family of closely related products has followed in its wake. These include the Titan and larger Atlas, as well as the smaller Lyra 1 and 2 interfaces. Importantly, although the original Orpheus is an eight-channel Firewire interface, all of these newer models are USB 2 interfaces.

So, the Titan is essentially an updated USB 2 version of the Orpheus, in the same 1U rack case with four mic preamps. The larger Atlas model is the same core product but expanded to provide eight preamps in a larger, 2U case. In contrast, the two compact Lyra models are both half-width 1U interfaces, yet they still manage to offer a remarkably comprehensive range of facilities. The baby of the family is the Lyra 1 which features one mic/line and one instrument/line input, with two analogue outputs plus optical S/PDIF digital I/O. The Lyra 2 looks very similar, but expands on its sibling’s capability with two full-function (mic/instrument/line) inputs and four analogue outputs, plus both optical and coaxial S/PDIF (the latter also accepting and generating AES3, if required), ADAT and an Ethernet port (see below) for digital I/O.

I previewed these two Lyra interfaces back in the November 2012 edition of SOS, just before the product’s official launch, but three years on we thought it time to revisit these interfaces to see how they have developed, and to run some bench tests. Both Lyra models share the same converters, clocking, USB interface and preamp technology as the Titan and Atlas models and, as the Lyra 2 is the more comprehensively equipped, that’s the model I was loaned for this review.

Overview

Despite the compact box and minimal front-panel controls, there’s actually quite a lot going on inside the Lyra, all organised via the same software control panel as supplied with the Orpheus and Titan. The only hardware panel controls are a power on-off button, a dedicated headphone volume control (for the front-panel quarter-inch socket), and a large assignable encoder knob with a push-button action. This can be allocated by the user to act as a master level control for whichever outputs are feeding the monitor speakers, with its push-button instigating a full mute. However, the action of this control is still not reflected on any of the Lyra’s output level meters, which can be rather perplexing and frustrating when the mute function has been activated accidentally and you can’t find out why there’s no output when the meters says there is!

The rear panel of the Lyra 2 offers an array of digital and analogue connections along with an IEC power socket. The rear panel of the Lyra 2 offers an array of digital and analogue connections along with an IEC power socket. Prism’s distinctive variation on the theme of bar-graph metering is found in a recessed section in the middle of the front panel, along with various status indicators, and a pair of high-impedance instrument inputs is provided on the left-hand side (just one for the Lyra 1). Internally, the analogue circuitry enjoys the same updates found in the Titan, including slightly less sensitive mic inputs with a 20dB pad facility to reduce the risk of overload with high-output mics, and a more powerful headphone output.

Rear-panel analogue I/O comprises a pair of XLRs for the mic inputs (with phantom power), two TRS quarter-inch sockets for the electronically balanced line inputs, and four more TRS sockets for the electronically balanced line outputs. The Lyra 1 differs in having a single mic input XLR and only two line output sockets. To help prevent digital overload when working with very small headroom margins on the analogue inputs, Prism Sound’s ‘Overkiller’ can be selected in the control app which engages a very fast-acting progressive limiter to control transient peaks up to 10dB above the normal digital clipping level.

The analogue input channel signal-processing options also include selectable 80Hz high-pass filters, a 20dB pad, polarity inversion, and a Mid/Side decoding matrix. The Lyra 2 also allows the high-pass filter to be converted into an RIAA de-emphasis filter to enable the connection of a stereo moving-magnet record-player pickup directly to the instrument inputs (or moving-coil pickups to the mic inputs), if required. Each pair of analogue, digital, and headphone outputs can be fed directly with the corresponding output signals from the computer’s USB 2 bus, or from a duplicate any of the other output pairs, or from separate dedicated mixers adjusted via a tab in the controller app. The mixer option allows any of the physical inputs to be combined with the DAW output signal for low-latency monitoring (less than 0.5ms).

Digital I/O is in the form of RCA-phono sockets for coaxial S/PDIF and AES3 in and out, as well as Toslink optical ports which are software-configurable for either S/PDIF or ADAT formats. (The Lyra 1 offers only S/PDIF via Toslink.) Sample-rate conversion is available for S/PDIF and AES3 signals, and the converter can be assigned either to the inputs or outputs. Prism’s four ‘SNS’ noise shaped dither facilities are also available when reducing the S/PDIF or AES3 output word length. The Lyra 2 also has word-clock in and out on BNCs, with options to run on an internal clock, the external BNC, or the selected digital input. Standard, double, and quad sample rates up to 192kHz are supported via S/PDIF and AES3, while the ADAT ports support base and double sample rates (the latter with S/MUX4). The ADAT source element of the output mixers in the control app is hidden if no ADAT signal is detected.

Both Lyra models communicate with the host computer via a USB 2 B-type socket, of course, supporting ‘Audio Class 2’ compliance for native operation with Mac OS X (10.5 onwards). ASIO drivers are supplied for both 32- and 64-bit Windows systems (Vista onwards), and the dedicated controller application is included for both Windows and Mac installations. Linux, iOS, and Android operating systems will also support the Lyra as a Class-2 native interface, but without the benefit of a controller app.

In summary, then, the Lyra 2 offers 12 physical inputs (eight ADAT, two S/PDIF, two analogue) and 16 outputs (eight ADAT, two S/PDIF, four analogue, two headphones), plus whatever the Ethernet port supports in the future. Lyra’s control-panel app is straightforward in normal use, and there is a button to access the online manual if help is needed to locate the lesser-used functions.

Ethernet Interfacing

The Ethernet port was an intriguing feature when the Lyra 2 was launched, and much was made of the potential connectivity it would offer as an AVB interface — even though the firmware support had not actually been completed when the Lyra was first introduced. For anyone not familiar with AVB, ‘Audio Video Bridging’ is a non-proprietary layer-2 audio-over-IP interface defined by an IEEE 802 technical standard, and designed to provide precise synchronisation and low latency between digital audio devices.

However, three years have now passed and that AVB port remains entirely dormant at the back of the Lyra 2. When I quizzed Graham Boswell, Prism Sound’s Sales and Marketing Director, about it he told me, “We planned an AVB capability [in Lyra 2] as we believed that, as an open standard, AVB offered fantastic opportunities. Unfortunately, that potential does not seem to have been realised. Internet switches are not incorporating AVB as standard yet, and very few player/recorder/streamer products are currently supporting it either. This is a great shame as users are going to lose out on the guaranteed low-latency of AVB in mixed signal networks that relied on the layer-2 elements of the AVB protocol.

This Audio Precision FFT plot shows the averaged noise floor from the line input with a  100Ω source termination. The highest spurious component lies below -145dBFS, which is at the limits of a  24-bit converter range.This Audio Precision FFT plot shows the averaged noise floor from the line input with a 100Ω source termination. The highest spurious component lies below -145dBFS, which is at the limits of a 24-bit converter range.“We did proceed with development of software to the extent of architecting a solution on our X platform [the computer interface employed in the Lyra/Titan family], but we’ve suspended work pending evidence of the progress of AVB in the marketplace. There’s no point in implementing something if there’s nothing for customers to connect it to!”

The lack of AVB support in the wider audio community is disappointing, and Prism Sounds’ decision not to progress AVB implementation in Lyra is quite understandable. However, other audio-over-IP protocols have been quite widely embraced in the audio industry, particularly the Dante format, so I asked if this was something Prism was considering? Graham replied only to say, “We are looking at Dante and how that might be incorporated in future...” So, no promises, then, but it seems the hardware platform could support it (or other Ethernet audio protocols) if there was a proven requirement amongst Prism’s customers. In the meantime, the Lyra’s Ethernet port remains a non-functional ‘future development’ option.

Technical Performance

As expected, the Lyra’s converters are identical to those of the Orpheus, Titan and Atlas products, with near-identical bench-test measurements taken with an Audio Precision system. The AES17 dynamic range figure from analogue line input to optical S/PDIF output measured 118dB (A-wtd), while the D-A performance measured 116dB (A-wtd). As I said in my Titan review, while these figures match the published specifications and indicate good levels of A-D performance on a par with my Crookwood mastering console’s converters, UAD’s Apollo, and Audient’s ASP880, there are products on the market that measure rather better in this particular respect. Contenders include Apogee’s Symphony (120dBA), Lynx’s Hilo (121.3dBA), and Lavry’s AD11 (123dBA). Similarly, the Lyra’s D-A matches the AES17 performance of Antelope’s Orion 32 and Benchmark’s DAC1, but is out-performed by Grace Design’s M905 (119.7dBA), Lynx’s Hilo (120.5dBA), Benchmark’s DAC2 HGC (125dBA), and Apogee’s Symphony (129dBA).

However, while the AES17 figures give a useful indication of the general quality of a converter, they certainly don’t tell the whole story, and other aspects of the Lyra’s technical tests proved extremely impressive — and better than the Titan in some cases! Crosstalk between adjacent channels measured a truly magnificent -122dB at 10kHz (ref +18dBu), with a THD figure of just 0.0003 percent — with very similar results being obtained for both line-in to S/PDIF out, and S/PDIF in to line-out.

This is the same as the plot above, but taken from the microphone input at maximum gain, again with a  100Ω source termination. There are no mains hum components at all from the internal power supply, just a  couple of very modest spurious signals around 8 and 16 kHz, but all below -80dBFS and completely inaudible in normal applications.This is the same as the plot above, but taken from the microphone input at maximum gain, again with a 100Ω source termination. There are no mains hum components at all from the internal power supply, just a couple of very modest spurious signals around 8 and 16 kHz, but all below -80dBFS and completely inaudible in normal applications.The minimum microphone input level for 0dBFS is -56dBu, which means that for a more realistic peak level of -12dBFS the source needs to provide -68dBu. Consequently, the Lyra will work happily with low-output mics and distant mic placements. The maximum mic input level, with gains at minimum and the pads engaged, is +19dBu (for 0dBFS out), and at maximum gain the EIN figure measured a respectable 127.6dB (150Ω source).

Looking at the instrument inputs, the minimum signal level for -12dBFS is -50dBu, while the maximum is +5dBu, which should accommodate active instruments without difficulty. The maximum line input and output levels are +18dBu for 0dBFS.

Evidence of Prism’s expertise in digital, clocking, PSU and analogue circuit design can be found in the spectrum analysis of the mic amp’s output at maximum gain (and terminated in 100Ω). No mains-related hum components were visible at all in the noise floor, and the few spuriae that were present were all comfortably below -80dBFS. At minimum gain (and for line inputs) they fell to below -145dBFS! (See AP Plots.)

Conclusion

Lyra provides genuine Orpheus levels of technical performance, but in a more compact, convenient and affordable form, while retaining a wealth of professional features and flexibility. USB 2 connectivity also ensures a good degree of future-proofing in the ever-changing world of computer interface standards.

In all probability, the Lyra interfaces will appeal most to those who want, but can’t afford — or who just don’t need the facilities of — the Titan and Orpheus interfaces. And there is a very substantial price saving to be made, with the Lyra 2 costing a great deal less than the Titan, and the Lyra 1 even less than that. Impressively, it also seems that all of Prism Sound’s interfaces are over 20 percent less expensive today than they were back in 2012 (in the UK, at least)!

Of course, Prism Sound are up against some very strong competition in the compact interface market, and while there is no doubt that their converters, clocking and analogue circuitry still set very high standards of audio performance, other manufacturers are now competing at a similar level.

The Lyra exudes quality and class, both in its physical construction and in the sound quality of anything passing through it. Stereo imaging is deep and wide, with a crystal-clear transparency of micro-details in the mix. The microphone preamps are clean and quiet, with that slightly larger-than-life character at the bottom end I associate with high-quality designs. For applications where a couple of analogue inputs and outputs is sufficient, the Lyra makes a very attractive option indeed.

Alternatives

High-quality, compact interfaces worthy of consideration include the Focusrite Forte, Lynx Hilo, Apogee’s and Avid Pro Tools’ Quartets, Matrix Halo ULN2 and the Antelope Audio Pure 2.

Published September 2015