Review of the Prism Sound Lyra 2 Audio Interface

April 4, 2015
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PRODUCT REVIEW

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Graham Boswell

The author (left) in ‘audio converter heaven’, with Prism Sound’s Director of Sales & Marketing, Graham Boswell.

If I was to say that a face to face catch up with Prism Sound’s Graham Boswell was overdue, then I would win the prize of the week for understatement.  It had been nearly 30 years since we had last worked together, at the wonderful Neve Electronics in 1984 and, finally, here we are standing in the reception area of Prism’s HQ in the pretty village of Stretham, north of Cambridge, in the UK.  Although Graham and I had done a little bit of catching up by phone over the last few years it was time to squeeze 30 years of history into a single day spent touring the Prism facility, getting some sneak previews of new products (sorry you’ll have to wait for the press release!) and, of course, talking audio converter design.

I had wanted to review a Prism Sound audio interface for some time and Graham kindly let me borrow a Lyra 2, so now I had the opportunity to take some of the best audio interface technology in the world, into my home studio and discover if I really could hear the difference that very high specification converters could bring to my recording and monitoring environment.

 

Audio Facilities

The Lyra takes the audio path and clock circuitry from the renowned Orpheus multiple interface and offers it in a smaller format.  In the case of the Lyra 2 (there is also a Lyra 1) this translates into 2 in, 4 out, analogue interface plus digital inputs and outputs as stereo AES3 or S/PDIF, or up to 8 channels of digital I/O on the ADAT optical format, plus stereo headphones.  Each of the analogue audio inputs can be selected for either mic, line or DI use (each with their own input socket) with appropriate gain ranges and facilities.

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As the Lyra provides high end mic amps which might be used on location recording, it’s great to see a built in MS matrix for use with a mid side microphone set-up.

Most audio I/O is on the rear panel but helpfully the two DI inputs, output level control, headphone jack, level metering and key status indicators are all front panel located and well laid out.

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The electronics are housed in a robust steel case with an internal, shielded mains PSU and, with the feet removed, the unit can be rack mounted with an optional 1RU kit.

 

Getting Connected

Although the unit can be configured to run in a pre-set stand-alone configuration, the more usual mode of operation will be by USB 2.0 connecting to a host recording computer.  A driver is required for Windows but Mac is supported natively.  A control panel app provides access to all of the unit’s control settings and level monitoring.

 

Synronisation, sample rates and SRC

The unit has a very high quality internal clock which can be routed to either the S/PDIF, ADAT or Wordclock outputs.  Alternatively, you can sychronise the Lyra to an external clock by using the DI or ADAT sync source, or from a studio wide master clock source to the Lyra’s Wordclock BNC connector.

Sample Rate conversion is available on digital inputs or outputs and is extremely flexible so, for example, you could be running a session at 88.2kHz and simultaneously derive a 44.1kHz digital output for a client mix.

24-bit recording and playback is available at all popular sample rate frequencies from 44.1kHz to 192kHz.

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The control panel app provides access to the unit’s session settings including sample rate, SRC on/off and, for Window’s operation, buffer settings for the USB interface (applies to both WDM and ASIO drivers) and an additional ASIO buffer setting.  For Mac operation these are all handled automatically.

Two buttons on the RHS of the screen allow settings to be saved and loaded from disk.  The green Help button opens the online version of the user manual in a separate browser window.

 

Inputs

prism-6An Inputs tab on the control app provides access to all of the input controls. Each of the analogue inputs can be selected to either mic, line or DI.  Line input sensitivity can be preselected to either between +4dBu and -10dBV nominal, while mic and DI gain are set by on-screen faders, next to which sit high resolution level meters with overload indicators.  Mic inputs get individual phantom power switching, 20dB pads, plus access to the switchable MS input matrix.  All inputs have switchable high pass filters or RIAA de-emphasis filters for DJ use, phase reverse, plus soft limiters to prevent accidental digital overs.

The digital source can be switched between coax and optical S/PDIF inputs, and ULOK and ASNC indicators are provided.  ULOK (unlock) is lit when no S/PDIF carrier is detected at the selected input; ASNC (asynchronous) is lit when the incoming carrier is not locked to Lyra’s selected sync source.  In ADAT modes, ULOK and ASNC indicators are also provided for the ADAT/SMUX inputs.

 

Outputs

prism-9The app’s Outputs tab provides control access to the four analogue outputs, the stereo digital out and the headphone feed.  Analogue line outputs can be switched to either +4dBu (0dBFS=+18dBu) or -10dBV (0dBFS=+6dBu) nominal, to suit the destination device sensitivity.  All outputs have high resolution level meters, again with overload indicators.

The stereo digital output can fed as either 24 bit or 16 bit with a choice of dither and noise shaping algorithms using Prism Sound’s proprietary SNS (Super Noise Shaping) process.  If the sample rate converter is selected, then a separate sync source and sample rate can be chosen.

Each of the outputs can be switched to follow a single output level control which is controllable both on screen and via the unit’s front panel control.  This can be locked to prevent accidental adjustment.

The source which feeds each of the output pairs can be fed from the DAW (USB), its own DSP mixer (see below) or from another output’s mixer (so effectively parallel outputs).  There are additional buttons to send any one of the output pairs directly to the headphones.

 

On-board Mixing

prism-7Providing ‘on board’ low latency mixing is still pretty well essential, especially for vocalists, so they can hear themselves on headphones without the echo which latency through computer based mixing still suffers from.  The Lyra has individual DSP based, ultra low latency buss mixers for each of its outputs which allows you to derive mixes which, when tracking, might typically be allocated for headphones, main and nearfield monitor speakers and a fourth mix which feeds the S/PDIF output, perhaps used to feed a stand-alone digital backup recorder.

Each source to each mixer has its own pan control, solo and mute buttons and a long throw fader with level meter.  Each input pair can be linked as a stereo feed with a balance control replacing the individual pan pots.  The DAW feed is treated as a stereo source by default.

The resultant mix has its own stereo output fader with level meter and mute button.

 

Audio Specifications

The published audio specifications for the Lyra are pretty mouth watering, so before I connected the unit into my recording set-up, I did a quick tech spec run through my Neutrik TT402 Analogue Test Set.  This would provide a real world, analogue in, analogue out benchmark.  I was particularly interested to see how the Lyra’s distortion and noise performance would compare with my two MOTU Ultralite interfaces.

With either of the line inputs routed to any of the line outputs, so low is Lyra’s distortion, that you have to measure at high levels to see any THD residual above the very low noise floor.  I settled on measuring at +15dBu in/out.  At any audio frequency, I measured THD below 0.001% which is getting on for a factor of 10 better than my MOTU interface.

Terminating the line input and with the unit set to unity gain, I measured an output noise figure of -94dBu (un-weighted) across the 22Hz to 22kHz bandwidth.  This is 10dB better than the -84dBu measured on both my MOTU units when set up identically.

Round trip, dynamic range measured at 112db which is in line with the quoted input and output dynamic ranges of 116dB and 115db respectively.

Low end frequency response is essentially flat down to around 10Hz whilst HF response is only limited by the sampling frequency in use, so for my preferred 88.2kHz rate this translates into a flat response until around 30kHz and 3dB down at 44kHz.

Crosstalk between channels was below the noise floor at all frequencies, so of no practical concern.

The performance of the mic and DI inputs is in the same league, with similar distortion and frequency response figures.  Microphone equivalent input noise, measured at full gain (65dB),  was an impressive -128dB with the input terminated at 150 ohm (typical mic source impedance) and also excellent at a mid range gain of 40db, measuring at -127.5dB and much better than a lot of boutique mic amps on the market.

Analogue outputs are properly electronically balanced, meaning that both hot and cold legs are driven (some lesser units use what’s called ‘impedance balancing’ so that only the hot leg contains audio) and the outputs can be unbalanced with no loss of level.  Maximum analogue I/O level is +18dBu which is a bit lower than some other analogue gear.  However with such a wide dynamic range available, there are no practical issues as long as you keep an eye on feed levels from external audio mics pre-amps and analogue processors feeding the Lyra’s line inputs.

 

Time to listen

So into the studio and I connect up the Lyra 2 to my recording system which is based around a very quiet PC running Windows 7 and Sonar.  Monitoring is via PMC DB1+ speakers.

First stop was to connect a pair of analogue outputs from the Lyra to my monitoring system and listen to some recently recorded 88.2kHz source material.

Even when dealing with line level audio, a 10db improvement in the noise floor begins to make a positive impact when doing critical monitoring of sources within the mix.  The immediate audible impression is one of clarity, improved location of sources within the stereo sound field and (for me) an unexpected improvement of low end smoothness from my PMCs, at higher monitoring levels.

I decided to give the Lyra an even more severe test.  As the Lyra 2 provides two pairs of analogue outputs, I looped analogue outputs 1 and 2 back into the two analogue line inputs and routed these in turn to analogue outputs 3 and 4.  With the simple addition of a couple of balanced splitter cables and a balanced passive switcher, I was now able to switch between;

88.2kHz DAW audio to Lyra Analogue Output to Monitor Loudspeakers

and

88.2kHz DAW audio to Lyra Analogue Outputs to Lyra Analogue Inputs to Lyra Analogue Outputs to Monitor Loudspeakers

I had expected to report that I could just about detect a subtle difference between the two feeds, bearing in mind the alternative monitor path was going through an additional A-D, D/A chain, but to my ears the two paths sounded identical.  This has very positive implications if you wish to use the Lyra 2 to insert an analogue processing chain across the 2-buss or within an analogue based mastering setup. (I’ll come back to that application a little later).

To get another perspective, I switched the Lyra to 44.1kHz and spent some time listening to a couple of classic jazz tracks.  First up was ‘Blue Velvet’, featuring the legendary saxophonist Willis “Gator” Jackson and the jazz guitarist Pat Martino.  First thing which struck me was the immediate increase in depth of the mix compared to my normal monitoring set up.  Willis Jackson sounds like he is actually standing up front on stage, piano left but noticeably further back. Double bass player standing a couple of meters behind Willis, drummer playing brushes to the right hand side of the bassist.  Then at 2:56 into the track, Pat Martino takes over lead duties and there he is front of stage slight to right of centre.  I kid you not.  If you close you eyes, you can soon forget you’re listening to a 16 bit/44.1kHz reproduction of a performance.

Staying with jazz, I turned to the Bill Withers composition ‘Use Me’ as recorded live by Patricia Barber in 1999 at the Green Mill Jazz Club in Chicago.  This starts with a very melodic solo double bass, then some percussion just before Patricia comes in with vocals and later Hammond B-3 organ.  It was originally recorded in analogue and then mastered for Vinyl, CD and later SACD release.  The double bass reproduction via the Lyra is quite simply stunning, solid positioning in the stereo field and no audio colouring.  And you can really hear the whole length of the instrument even through my diminutive PMC’s.  Patricia Barber’s vocals are nicely controlled and again you begin to forget you’re listening to digital reproduction outputting in analogue to a pair of loudspeakers.

By now you may be wondering why I’ve wandered off into review a couple of classic Jazz albums rather than the Lyra, but that is the whole point about this Prism Sound converter.  It is, to all intents and purposes, invisible.  Only those foks who actually want an audio interface to impart audio colouring as a ‘non optional’ feature will be disappointed.

 

Recording

As a recording interface, the same superb audio quality is evident.  The mic amps are transparent.  However, if ‘transparent’ is not to your taste then you have the option to use another mic amp brand then come into the digital world in the sure knowledge that the Lyra will add no audio footprint to your preferred ‘classic’ mic amp.  The very low noise floor means you should be able to record with plenty of spare headroom, so avoiding accidental digital clipping.  However if you are recording a very dynamic and unpredictable source, then the Lyra 2 has switchable ‘Overkiller’ limiters which will provide 5 or 6 db of additional headroom using a soft clipper type limiter circuit, enough to cope with the occasional high peaks from say a close miked drum kit.

 

Mastering applications

With the facilities available in the Lyra 2 you have the essential ingredients for a stereo mastering interface.  Assuming you receive 24 bit, high sample rate, digital source material you have the means to feed an analogue mastering chain, then re-enter the digital world via the Lyra’s line inputs, and also provide an analogue monitor feed via the second set of analogue outputs.

 

Support and advice

In terms of further technical information and advice, Prism Sound publish a more detailed set of technical specifications for their products than just about any other audio manufacturer I can think of.  The same evidence of thoroughness is evident in the depth of advice and tips available for the Lyra unit, including a very useful and detailed guide to Optimising your Windows PC for audio here.  I’ve already spotted half a dozen issues I need to attend to in my own PC setup to ensure that my recordings stay glitch free.

 

In summary

It may not seem intuitive that an audio interface with relatively limited I/O might be one of the most expensive items sitting in your studio.   Yet if we strive so hard to capture a great performance in all its glory and nuance, why would we compromise on such an essential part of the recording, mixing and monitoring chain?  It’s perhaps time to re-evaluate priorities and give your studio the quality of converters it deserves.  The Prism Sound family of converters are among the best in the world.  The Lyra 2 is highly recommended.

Useful Links

www.prismsound.com

You can also find a whole bunch of useful information including User Manual and other reviews at Audio Gear.  Click on the link below

Audio-Gear-Mini-15  Lyra 2 Database Listing

Robert Campbell
April 2015

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