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Prism Sound Orpheus

Audio & MIDI Interface [Mac/PC]
Published September 2008
By Hugh Robjohns

Prism Sound's Orpheus interface brings the company's high–end digital conversion technology within reach of the project studio owner for the first time.

Prism Sound OrpheusPrism Sound are a British manufacturer, mainly associated with very high–end digital converter technology, although they're no strangers to state–of–the–art analogue thanks to their involvement with the Maselec product range. They're not a company most would have expected to be working in project studio territory — at least, not until the launch of their new interface.

The Orpheus is a 1U, rackmounting, multi–channel Firewire audio interface with eight analogue line inputs and outputs (switchable for +4dBu or –10dBV operation), linked directly to eight Prism A–D and D–A converters. Four of the input channels also have very high–quality microphone preamps (with gain from 10 to 65dB in 1dB increments, switchable phantom power and M/S stereo decoding matrices). Moreover, the first two preamps have front–panel high–impedance DI input sockets, and can be switched to include RIAA de–emphasis so that turntables can be connected directly. The line inputs are electronically balanced, but will accept unbalanced inputs without problems, and Prism state that the Orpheus employs the same fully balanced architecture and the same isolation between analogue and digital domains as their high–end products. A second Firewire port on the rear panel enables additional Orpheus units to be daisy–chained to create larger interfaces, if required. The Orpheus also provides MIDI in and out, of course, and word clock in and out.

Drivers and control software are provided for both Windows (XP and Vista, with ASIO & WDM formats), and Mac OS 10.4 or later (for both Intel and PPC machines). The Orpheus's firmware and Control Panel software were both revised back in May, and the review model was running the latest versions (Firmware 1.02, Control Panel 1.03).

The Ins...

The Orpheus's front panel is astonishingly neat and simple in comparison to most interfaces. Apart from the two DI input sockets, there are just a few status LEDs, some very funky bar–graph meters, an assignable encoder wheel, two headphone volume pots and output sockets, and a power switch. It looks classy and elegant, and works very well; the meters will only give you a vague idea of signal levels, but your DAW (or other recorder's) metering will provide any additional resolution, should you need it.

In terms of input connectivity, then, the back panel has four combi XLR/TRS sockets for the first four channels with mic preamps, plus another four TRS sockets for the remaining four line inputs, and the front panel has two TS sockets for the DI inputs. Channels can also be linked together for stereo operation, but everything — apart from the monitor and headphone level controls — is controlled exclusively from the software controller application (see box overleaf) which runs behind a graphical interface in a separate screen on your computer.

All eight analogue input channels have a switchable 'Overkiller' circuit, which is a fast–acting but progressive limiter designed to catch and control brief transients that might otherwise overload the converter. This is a technology which has been included on other Prism converters for some time, and is very effective if you like to run things with little headroom.

The Orpheus also has a stereo digital input and output which is compatible with both S/PDIF and AES3, and its optical ports can be reassigned as an eight–channel ADAT interface, which can be used simultaneously. So that's a total of eight analogue inputs and up to 10 digital inputs, altogether! In ADAT mode, the system can support eight channels at base sample rates, or four at double rates, and a stereo sample–rate converter can be patched in to accommodate the digital input or the digital output. That allows a digital source with an incompatible sample rate to be connected easily, or a base–sample–rate output to be created to feed a CD recorder, say, when working with the DAW at 96kHz. Furthermore, the inclusion of Prism's SNS noise–shaping facility means that the word length can be reduced with mastering precision and quality!

As you would expect, the A–D and D–A conversion and clocking technology in the Orpheus is extremely sophisticated and is derived from Prism's state–of–the–art converters, while taking advantage of newer chip sets and design experience to maintain performance at a lower cost. All standard formats up to 24–bit, 192kHz are supported.

& The Outs

The rear panel of the Orpheus is packed with almost all of the unit's I/O. From left to right: built–in power supply, dual Firewire ports, MIDI and word clock I/O, electrical and optical digital I/O, eight TRS line outputs, four TRS line inputs and, finally, four combi XLR/TRS inputs.The rear panel of the Orpheus is packed with almost all of the unit's I/O. From left to right: built–in power supply, dual Firewire ports, MIDI and word clock I/O, electrical and optical digital I/O, eight TRS line outputs, four TRS line inputs and, finally, four combi XLR/TRS inputs.On the output side, there are eight analogue outputs, up to 10 digital outputs (ADAT plus S/PDIF or AES3), and a stereo headphone output — providing access, in theory, to 20 different channels at the same time. Each output can be switched between the corresponding DAW return (via the Firewire interface), or to derive the output from an independent digital input mixer facility, complete with a fader (which can be controlled from the assignable front–panel encoder knob, if required) and pan, cut, and solo functions. This feature allows the creation of latency–free foldback mixes, for example, but can also be used to provide a simple stereo or surround monitoring system (up to 7.1 channels) to control the monitoring signals from your DAW en route to active speakers. Of course, the digital signal processing involved here is to top–notch studio standards, and the worst–case propagation delay through the complete A–D and D–A signal path is an inconsequential 0.5ms at base sample rates, and proportionally less at higher sample rates. There is also a separate dedicated stereo headphone mixer, which feeds two front–panel quarter–inch headphone sockets, each with its own volume control.

The Orpheus can also operate as a stand–alone preamp and converter, once it has been configured from a computer, providing S/PDIF, AES3 or multi–channel ADAT digital outputs from the analogue inputs, and pre–configured monitoring. This is possible because, once set up using the Orpheus Control Panel applet, the settings are stored in non–volatile memory. When the unit is powered up it automatically restores the previous configuration, regardless of whether it can find a host computer or not.

The analogue outputs are electronically balanced, on TRS sockets, but they will work correctly (without a 6dB level drop) if connected to unbalanced inputs.

In Use

The Control Panel software is used to manage nearly all of the Orpheus's functions.The Control Panel software is used to manage nearly all of the Orpheus's functions.From the first moment you run audio through the Orpheus, its class and quality really shines through — it honestly is that obvious that this has come from a high–end stable with properly engineered analogue circuitry and superb converters. Stereo imaging is rock–solid and effortless, with massive depth and clarity. There is no trace of coloration, and the bandwidth extends smoothly at both ends. I've not had the chance to try the Orpheus against Prism's ADA8XR, but my recollections of that unit would suggest that the Orpheus would be a very close contender from a sound quality point of view. I have heard some reports that claim the Orpheus is even better than the ADA8XR, which is really impressive!

The microphone preamps are also very clean and very quiet, with an impressive degree of transparency and that larger–than–life quality at the bottom end that separates the really good designs from the OK designs. Again, there isn't any really obvious character or coloration, but equally, they don't sound bland in any way — just totally lifelike. I checked the phantom power supply voltage, and that proved a little low at 46.8V — although still well within the ±4V tolerance allowed in the specs. More importantly, the voltage didn't vary when I plugged in additional microphones. That indicates a very capable power supply, and users shouldn't have any problems regardless of how thirsty their capacitor mics might be.

I also got mean and dirty with the Orpheus and tried injecting some ground hum to see how well it would cope. I'm very pleased to report that it passed the test with flying colours. Clearly, the analogue circuitry and its earthing has been designed properly, and it would appear to be immune from ground–loop problems, which shouldn't be surprising given Prism's pedigree. Would that other manufacturers paid as much attention to this kind of detail.

The digital side of things also worked flawlessly. I was initially a little disappointed to discover that the conversion between S/PDIF coaxial and AES3 interfacing involved a (supplied) 'bodge lead'. Now I know that approach works most of the time, and I use the technique myself regularly and successfully, but it isn't kosher. AES3 not only has a different characteristic impedance and voltage (not forgetting its balanced configuration), but it also has different channel status bit assignments. I needn't have been concerned, though. Prism have done the job right, and when you change mode, the output voltage and channel status bits change too, so that the selected format really does comply with the standards. Proper engineering!

So from an analogue–to–digital converter point of view — and from a digital–to–analogue converter point of view — I have nothing but praise for the Orpheus. Great I/O capability, lots of flexibility, stunning sound. Brilliant. Most high–end analogue boxes tend to run hot too, thanks to all that Class–A circuitry, but the Orpheus was barely warm after several hours of use, and it only consumes 25W, so it's pretty kind to the planet.

Summing Up

At a fraction under £3000 in the UK, the Orpheus may well appear expensive, but it isn't when you consider what you are getting for your money: eight channels of truly high–end A–D and D–A, four superb mic preamps with DI inputs and RIAA facilities, stereo and ADAT digital I/O (with sample–rate conversion and word length facilities for the stereo interface), a very competent multi–channel Firewire interface, MIDI In and Out, and very flexible monitoring facilities.

There is no doubt in my mind that the Orpheus delivers seriously impressive results, and although I haven't used every interface that's out there, I can honestly say I've never heard a better system in such a compact form and at this price level. The unit is very easy to use and set up, it works well, and it was 100 percent stable and reliable for me. However, the Control Panel software really could do with a bit more polish so that it matches the very high standards set by the hardware. I wouldn't be put off buying the Orpheus because of the software, but I would find it a little frustrating and disappointing, which is a shame. Hopefully, Prism can address this minor weakness quickly and easily. Clearly, though, the Orpheus is destined to become a classic and widely used system interface. Where can I buy Prism shares?  

The Orpheus Control Panel

To achieve the control flexibility and the neatness of hardware design, pretty much all of the Orpheus's functions are controlled through the Control Panel applet. Nothing wrong with that — especially since it enables a wider range of features and facilities than would have been manageable using hardware controls. But sadly the controller in its current form lacks the polish and professionalism of the hardware unit, and that's a shame. Fortunately, it should be easily fixable given some development time. Don't get me wrong, though, everything seemed to work, and it was completely stable on my system (Windows Vista 32 SP1, 4GB RAM, 2.6GHz Quad Core processor).

The first issue for me was the fixed Control Panel window size. I run a dual 21–inch screen set up with 1680 x 1050 resolution on each screen, and I found the controller window was just a bit too small and fiddly to feel comfortable — I kept having to lean in towards the screen each time I wanted to change something, which isn't good. On higher–resolution screens I presume that problem would get even worse. Other than that everything seemed to work mostly as expected, and I didn't have to refer to the handbook very much at all. Amongst the minor bugs I found, the Help button refused to open the help manual (although it did flash open an impressively brief DOS command window at one stage!). Of greater concern, but little practical significance, was that the faders and bar–graph meters in the output pages didn't change to reflect level adjustments being applied with the rotary encoder. I could hear the level going up and down as I twiddled the knob, but the on–screen faders and meters didn't show those changes at all! Yet if I dragged the faders around with the mouse, the meters showed the level change as you would expect. That maybe not a huge problem to most users, but potentially very confusing and clearly not right.

I have an innate fear of using software to control the monitoring level because I've been near systems that have crashed and gone into massive howlrounds at maximum level. One such occasion managed to produce a pair of perfect smoke rings wafting gently from the tweeters of a pair of NS10s! The Orpheus didn't exhibit any crashing or random full–level problems during my time with it, although I have heard of early adopters suffering such calamities. Hopefully that problem was fixed in the firmware and controller updates earlier in the year. The only other thing that struck me about the monitoring facilities was that they could usefully be made more versatile with mono, dim, alternative output routing facilities and the like — the basics that you would expect to find on any decent monitoring controller. OK, so it could be argued that these facilities should be provided on the DAW, but it would be handy to be able to control some of these things from the Control Panel program too.

Published September 2008

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